Patient Preparation and Specimen Collection
Patient Preparation and Specimen Collection
PATIENT PREPARATION BEFORE DIAGNOSTIC AND LABORATORY PROCEDURES
Successful encounters with patients begin with a professional, respectful, and compassionate approach. Positive communications should begin by addressing the patient using proper titles such as Ms., Mrs., or Mr.; the use of inappropriate terms of endearment is a common patient complaint. First names may be used with the permission of the patient. Health care providers should also always introduce and identify themselves to the patient before explaining the upcoming procedure, when and where the procedure will take place, and the expected duration of the scheduled procedure.
The first step in any laboratory or diagnostic procedure is patient preparation or patient teaching before the performance of the procedure. This pretesting explanation to the patient or caregiver follows essentially the same pattern for all sites and types of studies and includes the following:
- Statement of the purpose of the study. The level of detail provided to patients about the test purpose depends on numerous factors and should be individualized appropriately in each particular setting.
- Description of the procedure, including site and method. It is a good idea to explain to the patient that you will be wearing gloves throughout the procedure. The explanation should help the patient understand that the use of gloves is standard practice established for his or her protection as well as yours. Many institutions require hand washing at the beginning and end of each specimen collection encounter and between each patient.
- Description of the sensations, including discomfort and pain, that the patient may experience during the specimen collection procedure. Address concerns about pain related to the procedure and suggest breathing or visualization techniques to promote relaxation. For pediatric patients, a doll may be used to “show” the procedure. Where appropriate, the use of sedative or anesthetizing agents may assist in allaying anxiety the patient may experience related to anticipation of pain associated with the procedure. Sensitivity to cultural and social issues, as well as concern for modesty, is important in providing psychological support.
- Instruction regarding pretesting preparations related to diet, liquids, medications, and activity as well as any restrictions regarding diet, liquids, medications, activity, known allergies, therapies, or other procedures that might affect test results. To increase patient compliance, the instructions should include an explanation of why strict adherence to the instructions is required.
- Recognition of anxiety related to test results. Provide a compassionate, reassuring environment. Be prepared to educate the patient regarding access to the appropriate counseling services. Encourage the patient to ask questions and verbalize his or her concerns.
Specific collection techniques and patient preparation vary by site, study required, and level of invasiveness. These techniques are described in the individual monographs.
- It is essential that the patient be positively and properly identified before providing care, treatment, or services. Specimens should always be labeled with the patient’s name, date of birth (or some other unique identifier), date collected, time collected, and initials of the person collecting the sample.
- Orders should be completed accurately and submitted per laboratory policy.
Most laboratory tests that require a blood specimen use venous blood. Venous blood can be collected directly from the vein or by way of capillary puncture. Capillary blood can be obtained from the fingertips or earlobes of adults and small children. Capillary blood can also be obtained from the heels of infants. The circumstances in which the capillary method is selected over direct venipuncture include cases in which:
- The patient has poor veins.
- The patient has small veins.
- The patient has a limited number of available veins.
- The patient has significant anxiety about the venipuncture procedure.
Venous blood also can be obtained from vascular access devices, such as heparin locks and central venous catheters. Examples of central venous catheters include the triple-lumen subclavian, implanted venous access port, and Groshong catheters.
Fetal blood samples can be obtained, when warranted, by a qualified health-care provider (HCP) from the scalp or from the umbilical cord.
Arterial blood can be collected from the radial, brachial, or femoral artery if blood gas analysis is requested.
Some general guidelines should be followed in the procurement and handling of blood specimens:
- The practice of an overnight fast before specimen collection is a general recommendation. Reference ranges are often based on fasting populations to provide some level of standardization for comparison. Some test results are dramatically affected by foods, however, and fasting is a pretest requirement. The presence of lipids in the blood also may interfere with the test method; fasting eliminates this potential source of error, especially if the patient already has elevated lipid levels. The laboratory should always be consulted if there is a question whether fasting is a requirement or a recommendation.
- Gloves and any other additional personal protective equipment indicated by the patient’s condition should always be worn during the specimen collection process. Standard Precautions online at DavisPlus provides a more detailed description of standard precautions.
- Stress can cause variations in some test results. A sleeping patient should be gently awakened and allowed the opportunity to become oriented before collection site selection. Comatose or unconscious patients should be greeted in the same gentle manner because, although they are unable to respond, they may be capable of hearing and understanding. Anticipate instances in which patient cooperation may be an issue. Enlist a second person to assist with specimen collection to ensure a safe, quality collection experience for all involved.
- Localized activity such as the application of a tourniquet or clenching the hand to assist in visualizing the vein can cause variations in some test results. It is important to be aware of affected studies before specimen collection.
- Hemoconcentration may cause variations in some test results. The tourniquet should never be left in place for longer than 1 min.
- Previous puncture sites should be avoided when accessing a blood vessel by any means to reduce the potential for infection.
- Specimens should never be collected above an IV line because of the potential for dilution when the specimen and the IV solution combine in the collection container, falsely decreasing the result. It is also possible that substances in the IV solution could contaminate the specimen and result in falsely elevated test results.
- Changes in posture from supine to erect or long-term maintenance of a supine posture causes variations in some test results. It is important to be aware of this effect when results are interpreted and compared with previous values.
- Collection times for therapeutic drug (peak and trough) or other specific monitoring (e.g., chemotherapy, glucose, insulin, or potassium) should be documented carefully in relation to the time of medication administration. It is essential that this information be communicated clearly and accurately to avoid misunderstanding of the dose time in relation to the collection time. Miscommunication between the individual administering the medication and the individual collecting the specimen is the most frequent cause of subtherapeutic levels, toxic levels, and misleading information used in the calculation of future therapies.
- The laboratory should be consulted regarding minimum specimen collection requirements when multiple tube types or samples are required. The amount of serum or plasma collected can be estimated using assumptions of packed cell volume or hematocrit. The packed cell volume of a healthy woman is usually 38% to 44% of the total blood volume. If a full 5-mL red-top tube is collected, and the hematocrit is 38% to 44%, approximately 2.8 to 3.1 mL, or [5 – (5 × 0.44)] to [5 – (5 × 0.38)], of the total blood volume should be serum. Factors that invalidate estimation include conditions such as anemia, polycythemia, dehydration, and overhydration.
- The laboratory should be consulted regarding the preferred specimen container before specimen collection. Specific analytes may vary in concentration depending on whether the sample is serum or plasma. It is strongly recommended that when serial measurements are to be carried out, the same type of collection container be used so that fluctuations in values caused by variations in specimen type are not misinterpreted as changes in clinical status. Consultation regarding collection containers is also important because some laboratory methods are optimized for a specific specimen type (serum versus plasma). Also, preservatives present in collection containers, such as sodium fluoride, may exhibit a chemical interference with test reagents that can cause underestimation or overestimation of measured values. Other preservatives, such as EDTA, can block the analyte of interest in the sample from participating in the test reaction, invalidating test results. Finally, it is possible that some high-throughput, robotic equipment systems require specific and standardized collection containers.
- Prompt and proper specimen processing, storage, and analysis are important to achieve accurate results. Specimens collected in containers with solid or liquid preservatives or with gel separators should be mixed by inverting the tube 10 times immediately after the tube has been filled. Handle the specimen gently to avoid hemolysis. Specimens should always be transported to the laboratory as quickly as possible after collection.
- Results that are evaluated outside the entire context of the preparatory, collection, and handling process may be interpreted erroneously if consideration is not given to the above-listed general guidelines.
Capillary Puncture: Assess the selected area. It should be free of lesions and calluses, there should be no edema, and the site should feel warm. If the site feels cool or appears pale or cyanotic, warm compresses can be applied over 3 to 5 min to dilate the capillaries. For fingersticks, the central, fleshy, distal portions of the third or fourth fingers are the preferred collection sites (Fig. A–1). For neonatal heel sticks, the medial and lateral surfaces of the plantar area are preferred to avoid direct puncture of the heel bone, which could result in osteomyelitis (Fig. A–2).
Venipuncture of Arm: Assess the arm for visibly accessible veins. The selected area should not be burned or scarred, have a tattoo, or have hematoma present. Even after the tourniquet is applied, not all patients have a prominent median cubital, cephalic, or basilic vein. Both arms should be observed because some patients have accessible veins in one arm and not the other. The median cubital vein in the antecubital fossa is the preferred venipuncture site. The patient may be able to provide the best information regarding venous access if he or she has had previous venipuncture experience (Fig. A–3). Alternative techniques to increase visibility of veins may include warming the arm, allowing the arm to dangle downward for a minute or two, tapping the antecubital area with the index finger, or massaging the arm upward from wrist to elbow. The condition of the vein also should be assessed before venipuncture. Sclerotic (hard, scarred) veins or veins in which phlebitis previously occurred should be avoided. Arms with a functioning hemodialysis access site should not be used. The arm on the affected side of a mastectomy should be avoided. In the case of a double mastectomy, the requesting HCP should be consulted before specimen collection.
Venipuncture of Hand and Wrist: If no veins in the arms are available, hands and wrists should be examined as described for the arm (see Fig. A–3). Consideration should be given to the venipuncture equipment selected because the veins in these areas are much smaller. Pediatric-sized collection containers and needles with a larger gauge may be more appropriate.
Venipuncture of Legs and Feet: The veins in the legs and feet can be accessed as with sites located on the arm, hand, or wrist. These extremities should be used only on the approval of the requesting HCP because veins in these locations are more prone to infection and formation of blood clots, especially in patients with diabetes, cardiac disease, and bleeding disorders.
Radial Arterial Puncture: The radial artery is the artery of choice for obtaining arterial blood gas specimens because it is close to the surface of the wrist and does not require a deep puncture. Its easy access also allows for more effective compression after the needle has been removed. The nearby ulnar artery can provide sufficient collateral circulation to the hand during specimen collection and postcollection compression (Fig. A–4).
Percutaneous Umbilical Cord Sampling: The blood is aspirated from the umbilical cord under the guidance of ultrasonography and using a 20- or 22-gauge spinal needle inserted through the mother’s abdomen.
Postnatal Umbilical Cord Sampling: The blood is aspirated from the umbilical cord using a 20- or 22-gauge needle and transferred to the appropriate collection container.
Fetal Scalp Sampling: The requesting HCP makes a puncture in the fetal scalp using a microblade, and the specimen is collected in a long capillary tube. The tube is usually capped on both ends immediately after specimen collection.
Locks and Catheters: These devices are sometimes inserted to provide a means for the administration of fluids or medications and to obtain blood specimens without the need for frequent venipuncture. The device first should be assessed for patency. The need for heparinization, irrigation, or clot removal depends on the type of device in use and the institution-specific or HCP-specific protocols in effect. Use sterile technique because these devices provide direct access to the patient’s bloodstream. When IV fluids are being administered via a device at the time of specimen collection, blood should be obtained from the opposite side of the body. If this is not possible, the flow should be stopped for 5 min before specimen collection. The first 5 mL of blood collected should be discarded.
Selection of Blood Collection Equipment
- Gloves and other personal protective equipment depending on the situation
- Materials to cleanse or disinfect the collection site (alcohol preparations [70% alcohol], povidone-iodine solution [Betadine], or green soap are the most commonly used materials)
- Gauze (to wipe collection site dry after cleansing)
- Sterile lancet (capillary puncture)
- Syringe and needle (arterial puncture or venipuncture)
- Vial of heparin and syringe or heparin unit dose
- Sterile normal saline in 50-mL syringe (for indwelling devices such as Groshong catheter)
- Sterile cap or hub (for indwelling devices when the cap or hub will be replaced after specimen procurement)
- Needle and holder for vacuumized collection tube system (arterial puncture or venipuncture)
- Butterfly or winged infusion set (venipuncture)
- Collection container (vacuumized collection tube, capillary tube, or Microtainer)
- Bandage (to cover puncture site after specimen collection)
In many cases when a blood sample is required, serum is the specimen type of choice. Plasma may be frequently substituted, however. Specimen processing is more rapid for plasma samples than serum samples because the anticoagulated sample does not need to clot before centrifugation. Plasma samples also require less centrifugation time to achieve adequate separation. Consult with the testing laboratory regarding recommended specimen types. The basic blood collection tubes are shown on the inside cover of this book. Consider latex allergy when selecting the collection equipment appropriate for each patient. Equipment used in specimen collection includes:
- Iatrogenic anemia is a significant concern for hospitalized infants. Anemia from chronic blood sampling can also be an issue for older adults who may also suffer malnutrition, dehydration, and diminished hematopoietic system response. The use of Microtainers allows for specimen collection from capillary sites. Many vacuum tubes, including blood culture tubes, are available in pediatric sizes to reduce collection volume. Advances in the technology of laboratory equipment has dramatically reduced, to microsamples, the amount of specimen required for testing.
- There have been other changes in equipment used specifically to address specimen collection issues in the pediatric and geriatric populations. The use of butterfly needles or winged infusion sets has become very popular with older adults who believe “they hurt less and are smaller” than conventional needles. Smaller needle size is a patient perception; butterfly and vacutainer holder needles are available in the same sizes. The way the butterfly needle is designed is the reason the patient perceives a less painful venipuncture. The butterfly wings are held by the phlebotomist and because the wings are closer to the needle than with a traditional vacutainer holder, the needle can be placed with greater precision; the tubing also allows for greater freedom and mobility in site selection to include surface veins (hand, wrist, scalp) that tend to “roll” when a traditional vacutainer holder is used. The skin of pediatric and geriatric patients is very delicate and tape was typically used to hold the bandage in place after the venipuncture. Many patients could not even tolerate the paper tape that is made with less adhesive. A self-adhesive wrap is now commonly used instead of tape; a section of the wrap is placed over the bandage and then the roll of adhesive is wrapped several times around the bandage. The wrap sticks to itself instead of the skin, very effectively holds the bandage in place, comes in every color imaginable, and is very popular with patients.
The procedures outlined here are basic in description. Positively identify the patient using at least two unique identifiers before providing care, treatment, or services. Label the appropriate tubes with the corresponding patient demographics, date, and time of collection before the specimen is collected. Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Pediatric and Geriatric Considerations: Two venipuncture-related concerns that are especially important pertain to the selection of specimen collection materials and the volume of specimen required.
Complications: There are a number of complications associated with invasive punctures of the skin. Pain is commonly associated with needles and while pain experienced during a needle puncture is usually mild, on a rare occasion the needle may strike a nerve causing severe and lasting pain. Hematoma results when blood leaks into the tissue during or after a needle puncture as evidenced by pain, bruising, and/or swelling at the puncture site. The swelling can cause temporary or permanent injury by compressing the surrounding nerves. Hematomas occur more often in elderly or frail patients, or those with difficult vessels to access. Prolonged bleeding is a complication that occurs with patients who are taking blood thinners such as aspirin or warfarin, or who have coagulopathies such as hemophilia. Bleeding or bruising can be prevented by applying direct pressure to the puncture site, once the needle has been removed, with gauze for a minute or two. The site should then be observed/assessed for bleeding or bruising. If no further action is required, the site can be covered by the gauze and an adhesive bandage or paper tape. Some patients experience a vasovagal reaction during the needle puncture procedure, evidenced by sweating (diaphoresis), low blood pressure (hypotension), fainting (syncope), or near fainting (near syncope). The potential for a fall injury is a significant concern related to vasovagal reactions. Other more unusual complications of needle puncture include cellulitis, phlebitis, seizures, inadvertent arterial puncture during a venipuncture, and sepsis. Sepsis can be caused by introduction of bacteria from the surface of the skin into the blood as the result of improper cleansing of the puncture site. Immunocompromised patients are at higher risk for developing this complication.
Capillary: Place the patient in a comfortable position either sitting or lying down. Positively identify the patient using at least two unique identifiers before providing care, treatment, or services. Label the appropriate tubes with the corresponding patient demographics, date, and time of collection before the specimen is collected. Assess whether the patient has allergies to the disinfectant or to latex if latex gloves or tourniquet will be used in the collection procedure. Use gloved hands to select the collection site as described in the site selection section. Cleanse the skin with the appropriate disinfectant and dry the area. Pull the skin tight by the thumb and index finger of the nondominant hand on either side of the puncture site and move them in opposite directions. Puncture the skin with a sterile lancet to a depth of approximately 2 mm, using a quick, firm motion. Wipe the first drop of blood away using the gauze. If flow is poor, the site should not be squeezed or the specimen may become contaminated with tissue fluid. Do not allow the collection container to touch the puncture site. Collect the sample in the capillary tube or Microtainer. The capillary tube should be held in a horizontal position to avoid the introduction of air bubbles into the sample. Microtainer tubes should be held in a downward-slanted direction to facilitate the flow of blood into the capillary scoop of the collection device. If a smear is required, allow a drop of blood to fall onto a clean microscope slide. Gently spread the drop across the slide using the edge of another slide. Apply slight pressure to the puncture site with a clean piece of gauze until bleeding stops, and then apply a bandage. Safely dispose of the sharps. Transport properly labeled specimens immediately to the laboratory.
Venipuncture Using a Syringe or Vacuumized Needle and Holder System: Place the patient in a comfortable position either sitting or lying down. Positively identify the patient using at least two unique identifiers before providing care, treatment, or services. Label the appropriate tubes with the corresponding patient demographics, date, and time of collection before the specimen is collected. Assess whether the patient has allergies to the disinfectant or to latex if latex gloves or tourniquet will be used in the collection procedure. Use gloved hands to select the collection site as described in the Site Selection section. Locate the vein visually, then by palpation using the index finger. The thumb should not be used because it has a pulse beat and may cause confusion in site selection or in differentiating a vein from an artery. Select the appropriate collection materials (needle size, butterfly, syringe, collection container size) on the basis of the vein size, vein depth, appearance of the collection site, patient’s age, and anticipated level of cooperation. Cleanse the skin with the appropriate disinfectant and dry the area. Select the appropriate collection tubes. If blood cultures are to be collected, disinfect the top of the collection containers as directed by the testing laboratory. Be sure to have extra tubes within easy reach in case the vacuum in a collection tube is lost and a substitute is required. Apply the tourniquet 3 to 4 in. above the selected collection site. Remove the sterile needle cap, and inspect the tip of the needle for defects. Pull the skin tight by placing the thumb of the nondominant hand 1 or 2 in. below the puncture site and moving the thumb in the opposite direction. The thumb is placed below the puncture site to help avoid an accidental needle stick if the patient moves suddenly. Ensure that the needle is bevel up and held at an angle of approximately 15° to 30° (depending on the depth of the vein) (Fig. A–5).
Puncture the skin with a smooth, firm motion using a sterile needle held by the dominant hand. A reduction in pressure is achieved when the needle has penetrated the vein successfully. Be sure to release the tourniquet within 1 min of application. Fill the vacuumized collection containers in the prescribed order of draw for the studies ordered. Tubes with anticoagulants can be gently mixed with the free nondominant hand as they are filled. When the required containers have been filled, withdraw the needle and apply pressure to the collection site until the bleeding stops. In most cases, a piece of gauze can be placed on the collection site and the arm bent upward to hold it in place while attention is given to disposing of the sharps safely. In cases in which a syringe is used, the barrel of the syringe should be gently pulled back during specimen collection and gently pushed in during the transfer to collection tubes. The vacuum in the collection container should not be allowed to suck the sample into the container, but rather the speed of entry should be controlled by the pressure applied to the barrel. The blood should gently roll down the side of the tube to prevent hemolysis. Transport properly labeled specimens immediately to the laboratory.
Radial Artery Puncture: Place the patient in a comfortable position either sitting or lying down. Positively identify the patient using at least two unique identifiers before providing care, treatment, or services. Label the appropriate tubes with the corresponding patient demographics, date, and time of collection before the specimen is collected. Assess whether the patient has allergies to the disinfectant or to latex if latex gloves or tourniquet will be used in the collection procedure. Assess if the patient has an allergy to local anesthetics, and inform the HCP accordingly. Glove the hands, and select the collection site as described in the site selection section. Ensure that the patient has adequate collateral circulation to the hand if thrombosis of the radial artery occurs after arterial puncture by performing an Allen test before puncture. The Allen test is performed by occlusion of the ulnar and radial arteries on the palmar surface of the wrist with two fingers. The thumb should not be used to locate these arteries because it has a pulse. Compress both arteries, and ask the patient to open and close the fist several times until the palm turns pale. Release pressure only on the ulnar artery. Color should return to the palm within 5 sec if the ulnar artery is functioning. If color returns above the wrist, the Allen test is positive. The Allen test also should be performed on the opposite hand. The wrist to which color is restored fastest has better circulation and should be selected as the site for blood gas collection. Be sure to explain to the patient that an arterial puncture is painful. The site may be anesthetized with 1% to 2% lidocaine (Xylocaine) before puncture. The index finger of the nondominant hand is placed over the site where the needle will enter the artery, not the site where the needle will penetrate the skin. The specimen is collected in an air-free heparinized syringe, which is held like a dart in the dominant hand and inserted slowly, bevel up, about 5 to 10 mm below the palpating finger at a 45° to 60° angle. When blood enters the needle hub, arterial pressure should cause blood to pump into the syringe. When enough specimen has been collected, the needle is withdrawn from the arm, and pressure is applied to the collection site for a minimum of 5 to 10 min. Immediately after the needle has been withdrawn safely from the arm, the exposed end of the syringe should be stoppered.
Samples should be gently and well mixed to ensure proper mixing of the heparin with the sample. The heparin prevents formation of small clots that result in rejection of the sample. The tightly capped sample should be placed in an ice slurry immediately after collection. Information on the specimen label should be protected from water in the ice slurry by first placing the specimen in a protective plastic bag. Transport properly labeled specimens immediately to the laboratory.
Indwelling Devices: Positively identify the patient using at least two unique identifiers before providing care, treatment, or services. Label the appropriate tubes with the corresponding patient demographics, date, and time of collection before the specimen is collected. Indwelling devices are either heparinized or irrigated after specimen collection. Before specimen collection, prepare the heparin in a syringe, if required. Allow the heparin (unit dose or prepared solution in the syringe) to equilibrate at room temperature during specimen collection. Cleanse the catheter cap or hub with povidone-iodine and 70% alcohol over 2 min. Using sterile gloves, remove the cap and attach a 5- or 10-mL syringe to the connector. Withdraw 5 mL of blood to be discarded. Clamp the catheter. (The Groshong catheter does not require clamping because it has a special valve that eliminates the need for clamping.) Attach another 5- or 10-mL syringe and begin collecting blood for transfer to the collection tubes. After the required specimen has been withdrawn, the device is heparinized by slowly injecting the heparin into the cap or hub of the device. Clamp the device 2 in. from the cap, remove the needle, and unclamp the device. Attach a new sterile cap or hub if the old one has been discarded. Groshong catheters are irrigated rather than heparinized. Irrigation of a Groshong catheter is accomplished by gently injecting 20 to 30 mL of sterile normal saline through the cap with moderate force. Remove the needle using some positive pressure (pressing down on the plunger) to prevent the solution from backing up into the syringe. Transport properly labeled specimens immediately to the laboratory.
Order of Draw for Glass or Plastic Tubes (Reflects Current CLSI [formerly NCCLS] Guideline: Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture, GP41-A6, Sixth Edition)
- First—Blood culture and other tests requiring sterile specimen (yellow or yellow/black stopper); blood culture bottle first, followed by sodium polyethanol sulfonate (SPS) tube for acid-fast bacilli specimens.
- Second—Coagulation studies (light blue [sodium citrate] stopper); sodium citrate forms calcium salts to remove calcium, and this prevents specimen clotting. Note: When using a winged blood or vacutainer collection set and the blue-top tube is the first tube drawn, a nonadditive red-top or coagulation discard tube should be collected first and discarded. The amount of blood in the discard tube needs to be sufficient to fill the winged collection set tubing’s “dead space” or fill one-quarter of the discard tube. This is done to ensure complete filling of the blue-top tube. The blue-top tube to be used for testing must be filled to ensure the proper ratio of blood to additive in the test specimen blue-top tube.
- Third—Plain or nonadditive (red or red/gray [gel] stopper); red/gray-top serum separator tube (SST) contains a gel separator and clot activator. SSTs are not appropriate for all testing requiring a serum specimen. They are generally unacceptable for therapeutic drug monitoring and serology studies. The laboratory should be consulted if there are questions regarding the use of SSTs.
- Fourth—Additive tubes in the following order:
Note: Always follow your facility’s protocol for order of draw.
Green stopper: Tube contains sodium heparin or lithium heparin anticoagulant (heparin inactivates thrombin and thromboplastin, and this prevents specimen clotting). For ammonia levels, use sodium or lithium heparin. For lithium levels, use sodium heparin.
Lavender stopper: Tube contains K3 EDTA (tripotassium EDTA forms calcium salts to remove calcium from the sample, and this prevents specimen clotting while preserving the integrity of the red blood cell wall).
White stopper: Tube contains K3 EDTA with gel (this preservative is intended for polymerase chain reaction [PCR] and branched DNA amplification [bDNA] techniques used in molecular diagnostics testing).
Blue/black stopper: Tube contains sodium citrate or sodium heparin with gel (this tube should be collected after EDTA but before any tube containing a liquid additive; this tube is intended for separation and harvesting of mononuclear cells from the whole blood matrix for use in molecular diagnostics testing).
Gray stopper: Tube contains potassium oxalate/sodium fluoride (the potassium oxalate acts as an anticoagulant, and the sodium fluoride prevents glycolysis).
Clear stopper: Tube contains PAXgene blood RNA preservative solution (this tube should always be collected last, and if no other tubes are collected, a discard tube should be collected first and discarded; this tube is preferred for subsequent isolation and purification of intracellular RNA from whole blood for PCR used in molecular diagnostics testing).
The patient should be informed that improper collection, storage, and transport are the primary reasons for specimen rejection and subsequent requests for recollection. If the specimen is to be collected at home, it should be collected in a clean plastic container (preferably a container from the testing laboratory). Many studies require refrigeration after collection. If the collection container includes a preservative, the patient should be made aware of the contents and advised as to what the precaution labels mean (caution labels such as caustic, corrosive, acid, and base should be affixed to the container as appropriate). When a preservative or fixative is included in the container, the patient should be advised not to remove it. The patient also should be told not to void directly into the container. The patient should be given a collection device, if indicated, and instructed to void into the collection device. The specimen should be carefully transferred into the collection container. Urinary output should be recorded throughout the collection time if the specimen is being collected over a specified time interval. Some laboratories provide preprinted collection instructions tailored to their methods. The specimen should be transported promptly to the laboratory after collection.
Wear gloves and any other additional personal protective equipment indicated by the patient’s condition. See Standard Precautions online at DavisPlus for a more detailed description of standard precautions. Assess whether the patient has allergies to the disinfectant or anesthetic, or to latex if latex gloves or catheter will be used in the procedure.
Random: These samples are mainly used for routine screening and can be collected at any time of the day. The patient should be instructed to void either directly into the collection container (if there is no preservative) or into a collection device for transfer into the specimen container.
First Morning: Urine on rising in the morning is very concentrated. These specimens are indicated when screening for substances that may not be detectable in a more dilute random sample. These specimens are also necessary for testing conditions such as orthostatic proteinuria, in which levels vary with changes in posture.
Second Void: In some cases, it is desirable to test freshly produced urine to evaluate the patient’s current status, as with glucose and ketones. Explain to the patient that he or she should first void and then drink a glass of water. The patient should be instructed to wait 30 min and then void either directly into the collection container or into a collection device for transfer into the collection container.
Clean Catch: These midstream specimens are generally used for microbiological or cytological studies. They also may be requested for routine urinalysis to provide a specimen that is least contaminated with urethral cells, microorganisms, mucus, or other substances that may affect the interpretation of results. Instruct the male patient first to wash hands thoroughly, then cleanse the meatus, void a small amount into the toilet, and void either directly into the specimen container or into a collection device for transfer into the specimen container. Instruct the female patient first to wash hands thoroughly, and then to cleanse the labia from front to back. While keeping the labia separated, the patient should void a small amount into the toilet, and then, without interrupting the urine stream, void either directly into the specimen container or into a collection device for transfer into the specimen container.
Catheterized Random or Clean Catch: “Straight catheterization” is indicated when the patient is unable to void, when the patient is unable to prepare properly for clean-catch specimen collection, or when the patient has an indwelling catheter in place from which a urine sample may be obtained. Before collecting a specimen from the catheter, observe the drainage tube to ensure that it is empty, and then clamp the tube distal to the collection port 15 min before specimen collection. Cleanse the port with an antiseptic swab such as 70% alcohol and allow the port to dry. Use a needle and syringe (sterile if indicated) to withdraw the required amount of specimen. Unclamp the tube.
Timed: To quantify substances in urine, 24-hr urine collections are used. They are also used to measure substances whose level of excretion varies over time. The use of preservatives and the handling of specimens during the timed collection may be subject to variability among laboratories. The testing laboratory should be consulted regarding specific instructions before starting the test. Many times the specimen must be refrigerated or kept on ice throughout the entire collection period. Explain to the patient that it is crucial for all urine to be included in the collection. Urinary output should be recorded throughout the collection time if the specimen is being collected over a specified time interval. The test should begin between 6 and 8 a.m. if possible. Instruct the patient to collect the first void of the day and discard it. The start time of the collection period begins at the time the first voided specimen was discarded and should be recorded along with the date on the collection container. The patient should be instructed to void at the same time the following morning and to add this last voiding to the container. This is the end time of the collection and should be recorded along with the date on the container. For patients who are in the hospital, the urinary output should be compared with the volume measured in the completed collection container. Discrepancies between the two volumes indicate that a collection might have been discarded. A creatinine level often is requested along with the study of interest to evaluate the completeness of the collection.
Catheterized Timed: Instructions for this type of collection are basically the same as those for timed specimen collection. The test should begin by changing the tubing and drainage bag. If a preservative is required, it can be placed directly in the drainage bag, or the specimen can be removed at frequent intervals (every 2 hr) and transferred to the collection container to which the preservative has been added. The drainage bag must be kept on ice or emptied periodically into the collection container during the entire collection period if indicated by the testing laboratory. The tubing should be monitored throughout the collection period to ensure continued drainage.
Suprapubic Aspiration: This procedure is performed by inserting a needle directly into the bladder. Because the bladder is normally sterile, the urine collected should also be free from any contamination caused by the presence of microorganisms. Place the patient in a supine position. Cleanse the area with antiseptic and drape with sterile drapes. A local anesthetic may be administered before insertion of the needle. A needle is inserted through the skin into the bladder. A syringe attached to the needle is used to aspirate the urine sample. The needle is then removed and a sterile dressing is applied to the site. Place the sterile sample in a sterile specimen container. The site must be observed for signs of inflammation or infection.
Pediatric: Specimen collection can be achieved by any of the above-described methods using collection devices specifically designed for pediatric patients. Appropriately cleanse the genital area and allow the area to dry. For a random collection, remove the covering of the adhesive strips on the collector bag and apply over the genital area. Diaper the child. When the specimen is obtained, place the entire collection bag in the specimen container (use a sterile container as appropriate for the requested study). Some laboratories may have specific preferences for the submission of urine specimens for culture. Consult the laboratory before collection to avoid specimen rejection.
BODY FLUID, STOOL, AND TISSUE
Wear gloves and any other additional personal protective equipment indicated by the patient’s condition. See Standard Precautions online at DavisPlus for a more detailed description of standard precautions. Assess whether the patient has allergies to the disinfectant or anesthetic or to latex if latex gloves will be used in the procedure.
Specific collection techniques vary by site, study required, and level of invasiveness. These techniques are described in the individual monographs.
Wear gloves and any other additional personal protective equipment indicated by the patient’s condition. See Standard Precautions online at DavisPlus for a more detailed description of standard precautions. Assess whether the patient has allergies to the disinfectant, anesthetic, contrast material, or medications or to latex if latex gloves, catheter, or tourniquet will be used in the procedure.
A sleeping patient should be gently awakened and allowed the opportunity to become oriented before preparation for the selected study. Comatose or unconscious patients should be greeted in the same gentle manner because, although they are unable to respond, they may be capable of hearing and understanding. Anticipate instances in which patient cooperation may be an issue. Enlist a second person to help with preparing the patient for the procedure to ensure a safe, quality testing experience for all involved.
Specific techniques and patient preparation vary by site, study required, age of the patient, and level of invasiveness. These techniques are described in the individual monographs.
The pediatric, maternity, special needs, and geriatric patient populations require special considerations when preparing for diagnostic studies.
Pediatric Considerations Preparing children for a diagnostic study depends on the age of the child. Encourage parents to be truthful about unpleasant sensations (cramping, pressure, pinching, etc.) the child may experience during the procedure and to use words that they know their child will understand. Toddlers and preschool-age children have a very short attention span, so the best time to talk about the test is right before the procedure. The child should be assured that he or she will be allowed to bring a favorite comfort item into the examination room, and if appropriate, that a parent will be with the child during the procedure. Special equipment (e.g., balloon-tip catheters to assist with retention of barium during a barium enema, foam wedges used to hold a limb in place during a nuclear scan, etc.) may be needed to assist with a successful study. Postprocedural recovery interventions, such as achieving adequate hydration, require close attention. The parents or caregivers must receive education to help them address specific needs and to be watchful for indications of a developing problem because pediatric patients cannot do these things for themselves.
Geriatric Considerations Elderly patients present with a variety of concerns when undergoing diagnostic procedures. Level of cooperation and fall risk may be complicated by underlying problems such as visual and hearing impairment, joint and muscle stiffness, physical weakness, mental confusion, and the effects of medications. A fall injury can be avoided by providing assistance getting on and off the examination table and getting on and off the toilet before and at the end of the exam. Older patients who are small in size compared to other adults also may receive a higher radiation dose than necessary if settings are not adjusted for their size. Elderly patients are often chronically dehydrated; anticipating the effects of hypovolemia and orthostasis can also help prevent falls. Special equipment (e.g., balloon-tip catheters to assist with retention of barium during a barium enema, foam wedges used to hold a limb in place during a nuclear scan, etc.) may be needed to assist with a successful study. Postprocedural recovery interventions, such as achieving adequate hydration, require close attention. Many older patients wish to maintain their independence. Their caregivers must receive education to help them address specific needs and to be watchful for indications of a developing problem; the limits of an older patient's physical and mental abilities may be an obstacle to independently carrying out the proper postprocedural care.
Radiation Safety Consultation with a HCP should occur before procedures involving radiation to discuss safety concerns regarding younger patients or patients who are lactating.
Pediatric Imaging Radiation risk is higher in young patients as they have more rapidly dividing cells than adults, and radiation damage occurs during cell division. Therefore, the younger the patient, the more radiation-sensitive the patient is. The Image Gently Campaign is an initiative of the Alliance for Radiation Safety in Pediatric Imaging. Information on the Image Gently Campaign can be found at the Alliance for Radiation Safety in Pediatric Imaging (www.pedrad.org/associations/5364/ig/). The campaign goal is to change practice by increasing awareness of the opportunities to promote radiation protection in the imaging of children. Three unique considerations in pediatric imaging are as follows:
- Children are considerably more sensitive to radiation than adults, which is evidenced in epidemiologic studies of exposed populations.
- Children have a longer life expectancy than adults, resulting in a larger window of opportunity for showing radiation damage.
- Children may receive a higher radiation dose than necessary if settings are not adjusted for their small size.
In addition to radiation safety, there are risks associated with the use of contrast media, especially iodinated contrast mediums. Pediatric patients have immature or incompletely developed organ and immune systems that do not tolerate the rigors of diagnostic testing as well as adults. Older adults are also potentially less able to tolerate some procedures because their systems are weakened by the natural aging process and interactions that may occur due to the presence of complex multisystem diseases.
- Although patients are still asked specifically if they have a known allergy to iodine or shellfish, it has been well established that the reaction is not to iodine, in fact an actual iodine allergy would be very problematic because iodine is required for the production of thyroid hormones. In the case of shellfish, the reaction is to a muscle protein called tropomyosin; in the case of iodinated contrast medium, the reaction is to the noniodinated part of the contrast molecule. Patients with a known hypersensitivity to the medium may benefit from premedication with corticosteroids and diphenhydramine; the use of nonionic contrast or an alternative noncontrast imaging study, if available, may be considered for patients who have severe asthma or who have experienced moderate to severe reactions to ionic contrast medium.
- If iodinated contrast medium is scheduled to be used in patients receiving metformin (Glucophage) for non-insulin-dependent (type 2) diabetes, the drug should be discontinued on the day of the test and continue to be withheld for 48 hr after the test. Iodinated contrast can temporarily impair kidney function, and failure to withhold metformin may indirectly result in drug-induced lactic acidosis, a dangerous and sometimes fatal side effect of metformin (related to renal impairment that does not support sufficient excretion of metformin).