Liver function tests

Liver Function Tests 

Definition

Liver function tests, or LFTs, include tests for bilirubin, a breakdown product of hemoglobin, and ammonia, a protein byproduct that is normally converted into urea by the liver before being excreted by the kidneys. LFTs also commonly include tests to measure levels of several enzymes, which are special proteins that help the body break down and use (metabolize) other substances. Enzymes that are often measured in LFTs include gamma-glutamyl transferase (GGT); alanine aminotransferase (ALT or SGPT); aspartate aminotransferase (AST or SGOT); and alkaline phosphatase (ALP). LFTs also may include prothrombin time (PT), a measure of how long it takes for the blood to clot.

Purpose

Liver function tests are used to aid in the differential diagnosis of liver disease and injury, and to help monitor response to treatment.

Precautions

Bilirubin: Drugs that may cause increased blood levels of total bilirubin include anabolic steroids, antibiotics, antimalarials, ascorbic acid, Diabinese, codeine, diuretics, epinephrine, oral contraceptives, and vitamin A.

Ammonia: Muscular exertion can increase ammonia levels, while cigarette smoking produces significant increases within one hour of inhalation. Drugs that may cause increased levels include alcohol, barbiturates, narcotics, and diuretics. Drugs that may decrease levels include broad-spectrum antibiotics, levodopa, lactobacillus, and potassium salts.

ALT: Drugs that may increase ALT levels include acetaminophen, ampicillin, codeine, dicumarol, indomethacin, methotrexate, oral contraceptives, tetracyclines, and verapamil. Previous intramuscular injections may cause elevated levels.

GGT: Drugs that may cause increased GGT levels include alcohol, phenytoin, and phenobarbital. Drugs that may cause decreased levels include oral contraceptives.

Description

The liver is one of the most important organs in the body. As the body's "chemical factory," it regulates the levels of most of the main blood chemicals and acts with the kidneys to clear the blood of drugs and toxic substances. The liver metabolizes these products, alters their chemical structure, makes them water soluble, and excretes them in bile.

Liver function tests are used to determine if the liver has been damaged or its function impaired. Elevations of certain liver tests in relation to others aids in that determination. For example, aminotransferases (which include ALT and AST) are notably elevated in liver damage caused by liver cell disease (hepatocellular disease). However, in intrahepatic obstructive disease—which may be caused by some drugs or biliary cirrhosis—the alkaline phosphatases are most abnormal.

Alanine aminotransferase

Alanine aminotransferase (ALT), formerly called serum glutamate pyruvate transaminase, or SGPT, is an enzyme necessary for energy production. It is present in a number of tissues, including the liver, heart, and skeletal muscles, but is found in the highest concentration in the liver. Because of this, it is used in conjunction with other liver enzymes to detect liver disease, especially hepatitis or cirrhosis without jaundice. Additionally, in conjunction with the aspartate aminotransferase test (AST), it helps to distinguish between heart damage and liver tissue damage.

Aspartate aminotransferase

Aspartate aminotransferase (AST), formerly called serum glutamic-oxaloacetic transaminase, or SGOT, is another enzyme necessary for energy production. It, too, may be elevated in liver and heart disease. In liver disease, the AST increase is usually less than the ALT increase. However, in liver disease caused by alcohol use, the AST increase may be two or three times greater than the ALT increase.

Alkaline phosphatase

Alkaline phosphatase (ALP) levels usually include two similar enzymes (isoenzymes) that mainly come from the liver and bone and from the placenta in pregnant women. In some cases, doctors may order a test to differentiate between the alkaline phosphatase that originates in the liver and the alkaline phosphatase originating in bone. If a person has elevated ALP, does not have bone disease and is not pregnant, he or she may have a problem with the biliary tract, the system that makes and stores bile. (Bile is made in the liver, then passes through ducts to the gall bladder, where it is stored.)

Gamma-glutamyl transferase

Gamma-glutamyl transferase (GGT), sometimes called gamma-glutamyl transpeptidase (GGPT), is an enzyme that is compared with ALP levels to distinguish between skeletal disease and liver disease. Because GGT is not increased in bone disorders, as is ALP, a normal GGT with an elevated ALP would indicate bone disease. Conversely, because the GGT is more specifically related to the liver, an elevated GGT with an elevated ALP would strengthen the diagnosis of liver or bile-duct disease. The GGT has also been used as an indicator of heavy and chronic alcohol use, but its value in these situations has been questioned recently. It is also commonly elevated in patients with infectious mononucleosis.

Bilirubin

Bilirubin, a breakdown product of hemoglobin, is the predominant pigment in a substance produced by the liver called bile. Excess bilirubin causes yellowing of body tissues (jaundice). There are two tests for bilirubin: direct-reacting (conjugated) and indirect-reacting (unconjugated). Differentiating between the two is important diagnostically, as elevated levels of indirect bilirubin are usually caused by liver cell dysfunction (e.g. hepatitis), while elevations of direct bilirubin typically result from obstruction either within the liver (intrahepatic) or a source outside the liver (e.g. gallstones or a tumor blocking the bile ducts). Bilirubin measurements are especially valuable in newborns, as extremely elevated levels of unconjugated bilirubin can accumulate in the brain, causing irreparable damage.

Ammonia

Analysis of blood ammonia aids in the diagnosis of severe liver diseases and helps to monitor the course of these diseases. Together with the AST and the ALT, ammonia levels are used to confirm a diagnosis of Reye's syndrome (a rare disorder usually seen in children and associated with aspirin intake), which is characterized by brain and liver damage following an upper respiratory tract infection, chickenpox, or influenza. Ammonia levels are also helpful in the diagnosis and treatment of hepatic encephalopathy, a serious brain condition caused by the accumulated toxins that result from liver disease and liver failure.

Preparation

Preparation requirements for all these tests vary from laboratory to laboratory, so it is generally considered best that the patient be in a fasting state (nothing to eat or drink) after midnight the day before the test(s).

Aftercare

Because many patients with liver disease have prolonged clotting times, it is important to monitor the puncture site for bleeding after blood is drawn (venipuncture).

Risks

Risks for this test are minimal, but may include slight bleeding from the blood-drawing site, fainting or feeling lightheaded after venipuncture, or hematoma (blood accumulating under the puncture site).

Normal results

Reference ranges vary from laboratory to laboratory and also depend upon the method used. However, normal values can generally be found within the following ranges, unless specified differently.

• ALT: 5-35 IU/L (values for the elderly may be slightly higher, and values also may be higher in men and in African-Americans)
• AST: 0-35 IU/L
• ALP: 30-120 IU/L
• GGT: Normal values for this test vary widely, depending on the laboratory performing the test, and the age and sex of the patient. For example, females less than 45 years old have lower values than both males and females over 45 years of age. Values in the newborn can be as much as five times higher than in adults.
• Bilirubin: (Adult, elderly, and child) Total bilirubin: 0.1-1.0 mg/dL; indirect bilirubin: 0.2-0.8 mg/dL; direct bilirubin: 0.1-0.3 mg/dL. (Newborn) Total bilirubin: 1-12 mg/dL. Note: critical values for adult: greater than 1.2 mg/dL. Critical values for newborn (requiring immediate treatment): greater than 15 mg/dL.
• Ammonia: Normal values for this test vary widely, depending upon the laboratory performing the test, the age of the patient, and the type of specimen. For example, values are somewhat higher in arterial than in venous blood.
• PT: 9-12 seconds.

Abnormal results

ALT: Values are significantly increased in cases of hepatitis, and moderately increased in cirrhosis, liver tumor, obstructive jaundice, and severe burns. Values are mildly increased in pancreatitis, heart attack, infectious mononucleosis, and shock. Most useful when compared with ALP levels.

• AST: High levels may indicate liver cell damage, hepatitis, heart attack, heart failure, or gall stones.
• ALP: Elevated levels occur in diseases that impair bile formation (cholestasis). ALP may also be elevated in many other liver disorders, as well as some lung cancers (bronchogenic carcinoma) and Hodgkin's lymphoma. However, elevated ALP levels may also occur in otherwise healthy people, especially among older people.

GGT: Increased levels are diagnostic of hepatitis, cirrhosis, liver tumor or metastasis, as well as injury from drugs toxic to the liver. Although the causes are unclear, GGT levels may increase with alcohol ingestion, heart attack, pancreatitis, infectious mononucleosis, and Reye's syndrome.

Bilirubin: Increased indirect or total bilirubin levels can indicate various serious anemias, including hemolytic disease of the newborn and transfusion reaction. Increased direct bilirubin levels can be diagnostic of bile duct obstruction, gallstones, cirrhosis, or hepatitis. It is important to note that if total bilirubin levels in the newborn reach or exceed critical levels, exchange transfusion is necessary to avoid kernicterus, a condition that causes brain damage.

Ammonia: Increased levels are seen in primary liver cell disease, Reye's syndrome, severe heart failure, hemolytic disease of the newborn, and hepatic encephalopathy.

PT: Elevated in acute liver injury, vitamin K deficiencies, and disorders with impair the absorption of vitamin K, including cholestasis.

Resources

Books

Pagana, Kathleen Deska. Mosby's Manual of Diagnostic and Laboratory Tests. St. Louis: Mosby, Inc., 1998.

Key terms

Cirrhosis — A serious disease of the liver caused by chronic damage to its cells and the eventual formation of scar tissue (fibrosis). The most common symptoms are mild jaundice, fluid collection in the tissues, mental confusion, and vomiting of blood. If left untreated, cirrhosis lead to liver failure and death.

Hemolytic disease of the newborn — Also known as erythroblastosis neonatorum, this is a condition in which a newborn's red blood cells are destroyed by antibodies that have crossed the placenta from the mother's blood. (Hemolytic disease begins in the fetus, in whom the disease is called erythroblastosis fetalis). Severe anemia caused by hemolytic disease is treated in the same way as other anemias, but when jaundice appears due to increased bilirubin, the jaundice is treated by exposing the infant to bright lights. In severe cases, exchange transfusion is required or brain damage may result.

Hepatic encephalopathy — Also called liver encephalopathy or hepatic coma, this is a disorder in which brain function deteriorates because toxic substances, which would normally be removed by the liver, accumulate in the bloodstream due to liver damage or disease. Early symptoms include subtle changes in logical thinking, personality and behavior. As the disorder progresses, signs of drowsiness and confusion increase until eventually the patient loses consciousness and lapses into coma.

Hepatitis — An inflammation of the liver, with accompanying liver cell damage or cell death, caused most frequently by viral infection, but also by certain drugs, chemicals, or poisons. May be either acute (of limited duration) or chronic (continuing). Symptoms include jaundice, nausea, vomiting, loss of appetite, tenderness in the right upper abdomen, aching muscles, and joint pain. In severe cases, liver failure may result.

Reye's syndrome — A rare disorder characterized by brain and liver damage following an upper respiratory tract infection, chickenpox, or influenza, almost entirely confined to children under age 15, and often related to aspirin ingestion for a viral infection. Symptoms include uncontrollable vomiting, often with lethargy, memory loss, disorientation, or delirium. Swelling of the brain may cause seizures, coma, and in severe cases, death.

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test(s),

n a clinical or laboratory procedure designed to evaluate constituents or functions of the body.

test, acetone,

n See test, ketone bodies.

test, ACTH-stimulation (Thorn's test),

n a test of adrenocortical reserve based on changes in the eosinophil count and urinary levels of 17-ketosteroids and 17-hydroxycorticoids as a result of intravenous infusion or intramuscular injection of ACTH.

test, allergy, intradermal,

n a test for allergy performed by injecting a preparation containing the suspected allergen into the dermis.

test, amylase

n a determination of serum amylase, which is useful in the diagnosis of acute pancreatitis and after operations in which the pancreas might have been injured. The Somogyi sarcogenic method is often used, and the results are given in
Somogyi units, defined as the amount of amylase needed to digest 1.5 g of starch in 8 minutes at 37°C. The normal range is 60 to 200 units/100 ml. The serum amylase is also elevated in mumps and other diseases of the salivary glands.

test, amyloid

n See test, Congo red.

test, antiviral antibody,

n antibody tests in viral diseases. Included are complement-fixation tests for poliomyelitis, psittacosis, and Coxsackie infections; hemagglutination-inhibition tests for mumps, influenza, and encephalitides; and neutralization tests.

test, Aschheim-Zondek

n.pr See test, pregnancy.

test, ascorbic acid, intradermal,

n a test for ascorbic acid deficiency based on the decoloration of an intradermal injection of a purple dye (2,6-dichlorphenol-indophenol). Normally with a wheal of 4 mm, using a dye concentration of N/300, decoloration occurs in 10 to 15 minutes.

test, basophilic aggregation

n a test for lead poisoning based on increased stippling of erythrocytes. More than 2% stippled cells are seen in lead poisoning. See also test, lead.

test, Bell's palsy,

n.pr simple clinical tests, such as motor function tests, in which the patient is asked to whistle, pucker the lips, smile, or wrinkle the forehead; also sensory function tests in which the patient is asked to taste sweet with sugar, sour with citric acid, bitter with quinine, and salt with sodium chloride.

test, Benedict's,

n a nonspecific copper reduction test for glucose in the urine. Cupric sulfate in the Benedict's reagent is reduced by glucose during the reaction to cuprous oxide, a reddish-orange precipitate.

test, bilirubin

n qualitative, presumptive, quantitative, or specific determinations for bilirubin in the urine and blood serum. Included are Gmelin's test and van den Bergh's test.

test, bleeding time,

n techniques for determining the time interval required for hemostasis to occur after a standardized wound has been made in the capillary bed. See also test, Duke's and test, Ivy's.

test, Brinell hardness

n.pr a means of determining surface hardness by measuring the amount of resistance to the indentation of a steel ball. Recorded as the Brinell hardness number (BHN); the higher the number, the harder the material. Generally indicative of abrasion resistance.

test, Bromsulphalein (BSP)

n a test of liver function based on the removal of a known quantity of Bromsulphalein from the blood in a measured period of time. Normal values are less than 5% retention at the end of 45 minutes with an intravenous dose of 5 mg/kg body weight. It is a useful test of hepatocellular disease and detoxifying ability but is not applicable in the presence of extrahepatic or intrahepatic obstructive jaundice.

test, Bunnell,

n.pr See test, Paul-Bunnell.

test, capillary resistance (Rumpel-Leede-Hess test, Gothlin's test),

n a test of capillary fragility based on the number of petechiae that develop when a standardized intraluminal positive pressure is applied to the capillaries either by a blood pressure cuff or a suction cup applied to the skin. See also test, tourniquet.

test, caries activity,

n a test used to predict the probability of developing new or increased decay; may include assessments of saliva and plaque for the presence of certain designated microorganisms or studies of salivary secretion and sugar clearance.

test, CO capacity (CO combining power test),

n a general measure of the alkalinity or acidity of the blood. Various normal adult ranges are given (e.g., 23 to 30 mEq/L of serum or 55 to 70 vol/100 ml of serum). A low value is found in diabetic acidosis, hyperventilation, certain kidney diseases, and severe diarrhea. A high value is found in excessive administration of ACTH or cortisone, intake of sodium bicarbonate, and persistent vomiting.

test, CO combining power,

n See test, CO₂ capacity.

test, cold bends,

n a mechanical test used for assessing ductility.

test, colorimetric caries susceptibility (Snyder's test),

n a method of determining the concentration of acid-producing bacteria in the saliva by use of bromcresol green in a culture medium. The reliability of this and other salivary bacterial tests for dental caries susceptibility is questionable.

test, Congo red,

n.pr a test for amyloidosis based on the more rapid disappearance (excess of 60% injected dye in 1 hour) of Congo red from the serum of affected patients than from that of normal individuals. Gingival biopsy and positive staining with methyl violet or crystal violet also indicate amyloidosis.

test, creatinine clearance

n a renal function test of exogenous creatinine clearance. It is a convenient clinical test of glomerular filtration rate. It is calculated as the quotient of the product of urine creatinine (mg/L) and urine volume (L/24 hr) divided by the serum creatinine concentration (mg/L). The normal value for young healthy adults of average size (1.73 M² body surface area) is 115 to 155 L/24 hr (±15%).

test, dermal,

n See test, skin.

test, Dick's (scarlet fever test),

n a skin test to determine susceptibility or immunity to scarlet fever. A positive test is indicated when an area of erythema and edema measuring more than 10 mm in diameter occurs 8 to 24 hours after an intradermal injection of a standardized erythrogenic toxin.

test, Duke's,

n.pr a test of bleeding time as indicated by the time that elapses before a puncture wound of the earlobe ceases to bleed. Normal range is 2 to 4½ minutes.

test, electric,

n a test to determine whether a pulp is vital.

test, erythrocyte sedimentation

n a macroscopic test of the blood used to detect certain pathologic conditions, particularly inflammation. The blood cells are allowed to settle in the presence of an anticoagulant and the time (sedimentation time) determined. The greater the time or rate, the more severe the condition. Pregnancy and menstruation affect the sedimentation.

test, flow,

n used in the ADA specification for dental amalgam; measured as the percentage shortening of a cylinder of the material.

test, fluorescent treponemal antibody, absorbed (FTA-APS)

n a modification of the original FTA test for syphilis that employs a protein preparation from the Reiter treponeme.

test for trigeminal nerve function,

n.pl three simple clinical tests for trigeminal nerve function: (1)
sensation: apply gentle touch, pinpricks, or warm or cold objects to areas supplied by the nerve and note responses; (2)
reflex: try the jaw jerk and eye and sneeze reflexes; (3)
motor function: test the patient's ability to chew and work against resistance and observe contraction of the masseter and temporal muscles by visual examination and digital palpation.

test, Foshay's,

n.pr a skin test for tularemia using the Foshay antigen.

test, Friedman's

n.pr See test, pregnancy.

test, glare,

n an examination of blade sharpness using a magnifying glass under light, which reveals dull edges as round, shiny, reflective surfaces.

test, glucose paper,

n a test in which paper is impregnated with glucose oxidase and other reagents (TesTape, Clinistix). When the paper is moistened with fresh urine, the presence of glucose will cause a change in the color of the paper.

test, glucose tolerance (GTT),

n a test for abnormalities of carbohydrate tolerance by glucose loading and subsequent serial measurements of the concentration of glucose in the blood. Graphic representation of the concentration and the elapsed time makes up the glucose tolerance curve. Abnormal curves occur in diabetes mellitus, thyrotoxicosis, Cushing syndrome, acromegaly, and pheochromocytoma.

test, Gothlin's,

n.pr See test, capillary resistance.

test, hardness,

n See hardness, Mohs; test, Brinell hardness; test, Knoop hardness; and test, Vickers hardness.

test, Hess's,

n.pr See test, capillary resistance.

test, histoplasmin

n a skin test to determine sensitization to
Histoplasma capsulatum. A positive test indicates past or present infection (histoplasmosis).

test, infectious mononucleosis,

n one of several tests for the diagnosis of infectious mononucleosis (e.g., Paul-Bunnell test).

test, intracutaneous,

n See test, skin.

test, intradermal,

n See test, skin.

test, Ivy's,

n.pr a test of bleeding time performed by making a standard wound and touching the blood with filter paper every 30 seconds until no blood appears on the paper. Normal range is 3 to 7 minutes.

test, Janet's,

n.pr a test to differentiate between functional and organic anesthesia. With the eyes closed, patients are instructed to say “yes” or “no” as they feel or do not feel the examiner's touch. In functional anesthesia, they will say “no,” whereas in organic anesthesia, they will say nothing.

test, ketone bodies (acetone test, Rothera's test)

n nitroprusside reaction tests for acetone and acetoacetic acid and the ferric chloride test for acetoacetic acid. Commercially prepared nitroprusside test tablets (Acetest) and powder (Acetone Test Denco) are available.

test, Kline's,

n.pr a flocculation test for syphilis based on the combination of the cardiolipin antigen with reagin to form grossly visible aggregates.

test, Knoop hardness,

n.pr a means of measuring surface hardness by resistance to the penetration of an indenting tool made of diamond. Produces an indentation that has a diamond or rhombic shape. Especially preferred for testing hardness of tooth structure.

test, laboratory,

n investigative procedures performed in the laboratory that are useful in the diagnosis of disease, including biopsy examination of tissue specimens, determination of type and characteristics of associated microorganisms, serology, blood and urine chemistry, hemogram (red cell count, hemoglobin content, white cell count, differential white cell count), and metabolic studies (basal metabolic rate).

test, LE,

n a test for lupus erythematosus based on the presence of a single (or multiple) homogenous basophilic inclusion(s) in polymorphonuclear leukocytes. Such LE cells have also been found in cases of rheumatoid arthritis, allergic reactions to penicillin, hydralazine toxicity, and “lupoid cirrhosis.” Thus the test is not definitive for lupus only; it is one of the diagnostic tests for causation.

test, lead,

n a test used to detect clinical lead poisoning or exposure to lead (e.g., coproporphyrinuria test, trace element analysis, urinary lead content test, and basophilic aggregation test).

test, Leede's,

n.pr See test, capillary resistance.

test, Mann-Whitney U,

n.pr a powerful nonparametric statistic test of significance between two means with unequal sample sizes.

test, Mantoux

n.pr an intracutaneous tuberculin test using either old tuberculin (OT) or purified protein derivative (PPD). A positive reaction read 24 and 48 hours after injection shows erythema and edema greater than 5 mm in diameter and indicates past or present tuberculosis.

test, Mazzini's

n.pr a flocculation test for syphilis.

test, Mohs,

n.pr See hardness, Mohs.

test, nontreponemal antigen,

n.pl serologic tests for syphilis using nontreponemal antigens. Such tests are not absolutely specific or sensitive for syphilis. Included are the Kline, Kahn, and Kolmer tests, and the VDRL slide test.

test, one-stage,

n See time, prothrombin.

test, oral glucose tolerance test (OGTT),

n the application of glucose to the body, typically administered orally, in order to determine the rate at which glucose is metabolized. Can be used to diagnose diabetes mellitus.

test, patch,

n (percutaneous test), a test for allergies that is performed by placing the suspected allergen in direct contact with the skin or mucosa. See also test, skin.

test, Paul-Bunnell,

n.pr a test for infectious mononucleosis based on increased agglutination of sheep red blood cells resulting from heterophil antibodies in the serum. The test is considered positive if dilution of serum of 1:80 or higher agglutinates the sheep cells. Elevated agglutinin titers are more likely to be found during the second or third week of the disease, but the serum may not become positive until 7 weeks have elapsed.

test, percussion,

n a method of examination executed by striking the tissues of the area being examined with the fingers or an instrument, listening for resulting sounds, and observing the response of the patient.

test, percutaneous

n See test, patch.

test, Phelan's

n.pr a common test for diagnosing carpal tunnel syndrome. In a positive Phelan's test, tingling or numbness is felt within one minute when the subject's hands are held with the wrists flexed (usually at a 90° angle).

test, phenolsulfonphthalein (PSP)

n a renal test that roughly estimates glomerular function by measuring the rate of excretion of the dye after intravenous injection. Normally, after 15 minutes, 25% or more of the dye should be excreted in the urine.

test, plasma ketone

n a test using nitroprusside for the detection of high levels of ketone bodies in the blood. The test is read 0 to 4 plus. A strongly positive reaction is seen in diabetic ketoacidosis.

test, prothrombin consumption (serum prothrombin time),

n a convenient screening test of the first stage of blood coagulation as determined by the quantity of prothrombin remaining after coagulation. The test reflects the formation of plasma thromboplastin, provided the one-stage prothrombin time of plasma is normal. See also time, prothrombin.

test, pulp,

n a diagnostic test to determine clinical pulp vitality and/or abnormality.

test, Reiter protein complement-fixation (RPCF)

n.pr treponemal antigen test for syphilis using extracts from the nonpathogenic Reiter treponeme.

test, reverse torque (RTT) (tork),

n a test used to determine the degree of osseointegration of an implant by applying a rotational force in the opposite direction originally used to set the implant into the bone; in essence, it measures the shear strength at the point where the implant meets the bone.

test, Rockwell,

n an indentation test for hardness of a material. A static load is placed on a steel ball or diamond point, and the depth of the indentation is measured on the instrument. The depth of the indentation is remeasured after the load is increased. The hardness number is related to the type of point used and to the depth of the indentation.

test, Rothera's,

n.pr See test, ketone bodies.

test, routine,

n a test or group of tests performed on most or all patients to detect relatively common disorders or to establish a base for further evaluation of a patient.

test, Rumpel-Leede-Hess,

n.pr See test, capillary resistance.

test, scarlet fever,

n See test, Dick's.

test, Schick,

n.pr a skin test to demonstrate the presence or absence of an immunity to diphtheria.

test, scratch (skin test),

n a test for allergies performed by placing a preparation containing the allergen on the skin and scratching the skin. A positive reaction is indicated by the formation of a wheal and flare.

test, serologic

n test of blood serum for the diagnosis of infectious diseases.

test, Snyder's,

n.pr See test, colorimetric caries susceptibility.

test, sterilizer,

n the periodic use of spore strip, color strip, or other microbial test to ensure that a sterilizer (autoclave, oven) is killing all microbes predictably.

test strip,

n a blood test used to check blood sugar levels in diabetics. The patient places a drop of blood on the strip, and the strip changes color according to the level of blood sugar present.

test, subcutaneous,

n See test, skin.

test, syphilis,

n a serologic test for syphilis based on the presence of a reagin, appearing during the second or third week of infec-tion. Included are the Hinton, Kahn, Kline, Mazzini, Wassermann, and
Treponema pallidum immobilization tests.

test, tension,

n an evaluation used to determine the presence or absence of attached gingiva within the oral cavity. The tongue, cheek, and lip are retracted to apply pressure at the mucogingival junction and make the alveolar mucosa taut.

test, thermal,

n the use of heat or cold as an aid in diagnosis (e.g., the use of heat or cold in testing the pulp).

test, Thorn's,

n.pr See test, ACTH-stimulation.

test, thromboplastin generation

n a test of the integrity of the first stage of blood coagulation and the nature of the defect. A patient's serum, plasma, or platelets are substituted in a system that is complete except for one of the factors to be tested for (antihemophilic factor, plasma thromboplastin antecedent, plasma thromboplastin component, or platelets), and the rate of thromboplastin generation is determined.

test, tourniquet

n a test for capillary fragility based on counting petechiae in a given area of the arm after application of the rubber cuff of a sphygmomanometer for 15 minutes.

test, transillumination,

n a test for a pulpless tooth in which the use of transmitted light shows a shadow of the root when the pulp is necrotic or has been replaced by a filling (not always reliable).

test, Treponema pallidum immobilization (TPI)

n a test to confirm syphilis by demonstrating the immobilization of
Treponema pallidum by specific antibodies in the serum of an infected individual; not widely used.

test, tuberculin,

n a test for past or present infection with tubercle bacilli. See also test, Mantoux.

test, tuberculin skin

n an intradermal injection of old tuberculin (OT) or purified protein derivative (PPD) to determine a specific sensitivity or susceptibility to tuberculosis.

test, tularemia,

n See test, Foshay's.

test, U, Mann-Whitney,

n.pr See test, Mann-Whitney U.

test, urea clearance,

n a clinical test of renal function determined by the clearance of urea from the plasma by the kidney each minute. Average normal value is 75 ml/min (75% to 125% of normal).

test, urine, routine,

n the routine examination of the urine, including amount, appearance, pH level, specific gravity, qualitative tests for sugar and protein, and microscopic examination of sediment.

test, van den Bergh's,

n.pr a test of hepatic function by measuring serum conjugated (“direct-reacting”) 1-minute bilirubin, total serum bilirubin, and, by difference, unconjugated (indirect) bilirubin. Obstructive jaundice and hemolytic jaundice give abnormal values.

test, VDRL (Venereal Disease Research Laboratory),

n.pr a serologic nontreponemal antigen test for the detection of syphilitic reagin by means of a reaction between the reagin and a standard antigen.

test, Vickers hardness,

n.pr a penetration type of hardness test using a square-based pyramid made of diamond.

test, vitality,

n the procedure using thermal, electrical, or mechanical stimuli to determine the response of the pulp in a tooth.

test, Wassermann,

n.pr a complement-fixation test for syphilis.

test, Zondek's,

n.pr See test, pregnancy.

tests, liver function,

n.pl tests to measure the severity of liver disease, aid in the differential diagnosis of the various types of disease of the hepatobiliary system, and follow the course of liver disease. Screening tests include urine bile, urine urobilinogen, Bromsulphalein (BSP) excretion, serum transaminases, thymol turbidity, cephalin-cholesterol flocculation, and van den Bergh's reaction (1 minute direct and total).

tests, pancreatic function,

n.pl tests of enzyme levels in blood and urine (amylase, lipase), fecal fat content, trypsin activity, nitrogen content, alteration of digestive capacity, and alteration of pancreatic secretion via duodenal intubation.

tests, pregnancy (Aschheim-Zondek test, Friedman's test),

n.pl biologic or chemical tests that determine pregnancy. The tests are usually based on changes in the ovaries of an animal injected with the urine of a pregnant woman. Included are the Aschheim-Zondek test (using mice or rats) and the Friedman test (using virgin rabbits). Male frogs and female and male toads are also used. A saliva test has also been used.

tests, pulmonary function,

n.pl tests used to evaluate respiratory function (e.g., tests of vital capacity, tidal volume, maximal breathing capacity, timed vital capacity, arterial blood gases).

tests, rapid reagin,

n.pl serologic tests for syphilis that permit rapid and economic screening in the field. Included are the rapid plasma reagin (RPR) test and the unheated serum reagin (USR) test.

tests, renal function,

n.pl quantitative tests including inulin or mannitol clearance for the glomerular filtration rate (GFR), paraaminohippurate (PAH) clearance for renal plasma flow, and the maximum rate of tubular excretion of paraaminohippurate and of reabsorption of glucose for the measurement of excretory and reabsorptive functions of the renal tubules. Clinical renal tests are used to assess the extent of renal impairment. They include blood urea nitrogen (BUN), nonprotein nitrogen (NPN), urea clearance, endogenous creatinine clearance, filtration fraction, phenolsulfonphthalein (PSP), and concentration tests.

tests, screening,

n.pl a group of tests especially chosen to detect specific abnormalities.

tests, skin,

n.pl tests to determine the sensitivity or susceptibility to infections by a specific agent, the presence of an allergy, or the presence of a nutritional deficiency. Included are the Mantoux, Schick, Dick, Frei, histoplasmin, and Foshay tests for infectious diseases (tests in which allergens are placed onto or into the skin) and the intradermal ascorbic acid, dermal, intradermal (intracutaneous), patch (percutaneous), scratch, and subcutaneous tests.

tests, thyroid function,

n.pl tests for thyroid function (e.g., radioactive iodine uptake, protein-bound iodine, basal metabolic rate, serum cholesterol, triiodothyronine suppression, thyroid-stimulating hormone tests).

tests, transaminase

n.pl tests for serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT). The normal value for serum glutamic oxaloacetic transaminase is 40 units or less; that for serum glutamic pyruvic transaminase is 35 units or less. The serum glutamic oxaloacetic transaminase value in myocardial infarction is 3 to 20 times the normal.

tests, treponemal antigen,

n.pl tests for syphilis using
Treponema pallidum or extracts from a treponeme as antigen. Included are
T. pallidum immobilization (TPI),
T. pallidum agglutination (TPA), fluorescent treponemal antibody (FTA), Reiter protein complement-fixation (RPCF), and
T. pallidum complement-fixation (TPCF) tests.

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liver

1. the large, dark-red organ located in the cranial portion of the abdomen, just behind the diaphragm. Its functions include storage and filtration of blood; secretion of bile; detoxication of noxious substances; conversion of sugars into glycogen; synthesis and breakdown of fats and temporary storage of fatty acids; and synthesis of serum proteins such as certain of the alpha and beta globulins, albumin, which helps regulate blood volume, and fibrinogen and prothrombin, which are essential blood clotting factors. See also hepatic.

2. a rich red-brown coat color in dogs that resembles the color of the organ.

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liver abscess

causes toxemia, possibly local signs of subacute abdominal pain, pain on percussion or palpation over the liver if peritoneal inflammation is present, when there may also be a positive paracentesis sample.

liver damage

damage to the liver parenchyma causing some degree of hepatic insufficiency.

liver displacement

may be because of a diaphragmatic hernia with the liver protruding into the thoracic cavity. Usually accompanied by dyspnea.

liver dullness

dullness on percussion over the right rib cage, used to help in defining the size of the liver which must be grossly enlarged to register a recognizable change.

liver dysfunction

the result of diffuse damage to the liver, e.g. in hepatitis. There may be clinical signs including photosensitization, jaundice, hepatic encephalopathy in the form of the dummy syndrome, dullness and anorexia, or there may be subclinical disease detectable by clinicopathological tests, e.g. hypoglycemia, hypoproteinemia, hyperammonemia. All of the functions of the liver will be affected at the one time.

liver enlargement

may be caused by neoplasia, congestion (as with heart failure), and infiltration by fat or inflammatory cells.

liver enzyme

when there is acute, diffuse damage to the liver some of its enzymes are liberated into the blood, where they can be measured. An indication of the severity of the damage can be obtained in this way. Different enzymes are used in each animal species.

liver failure

when liver function is inadequate to sustain life; the end-stage of liver dysfunction.

fatty liver

one affected with fatty infiltration.

fatty liver syndrome

see fat cow syndrome.

liver fluke

fasciolahepatica.

liver fluke disease

see hepatic fascioliasis.

liver function

summation of the functions of the liver.

liver function tests

biochemical tests capable of demonstrating that the liver's functions are, or are not, at full capacity. The sulfobromophthalein clearance test is the most commonly used in veterinary medicine.

liver inflammation

see hepatitis.

inherited liver insufficiency

occurs in several breeds of sheep and is characterized by the appearance of photosensitive dermatitis when the lambs begin to eat green feed. There is an accumulation of phylloerythrin in the blood and other biochemical indications of insufficiency, but the liver is histologically normal. Called also inherited photosensitization.

liver injury

damage to the hepatic parenchyma, possibly by massive trauma, but usually by an hepatic toxin. A common cause of hepatic insufficiency.

liver insufficiency

see liver dysfunction (above).

liver lobe torsion

see liver torsion (below).

liver melanosis

see hepatic lipofuscinosis.

liver meridian points

acupuncture points along the liver meridian.

liver necrobacillosis

a disease characterized by multiple liver abscesses, usually containing Fusobacterium necrophorum and resulting from infection from a chemical rumenitis which originated from carbohydrate engorgement and lactic acid rumenitis.

liver protectant

substance used for the treatment of liver failure. The important ones are choline, methionine, betaine, lecithin, vitamin B₁₂, selenium-vitamin E, essential phospholipids, glucose, fructose, vitamins E and B complex, and glucuronic acid.

liver rot

see acute hepatic fascioliasis.

liver rupture

is usually the result of severe trauma to the abdomen. In most cases there is massive hemorrhage into the peritoneal cavity, acute hemorrhagic anemia and mucosal pallor. Abdominal paracentesis recovers whole blood.

liver torsion

is usually restricted to a single lobe. Causes severe abdominal pain and severe vomiting.

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liver function tests

Clinical parlance for a battery of serum analytes that reflect the liver's metabolic reserve capacity

Liver function tests

Test ability to excrete

• Endogenous substances, eg bilirubin, bile acids, ammonia

• Exogenous substances, eg drugs, dyes, galactose

Test ability to metabolize

• Conjugation and synthesis of proteins

Elevated substances

• Liver disease, inflammation or necrosis–↑ transferases, other enzymes, vitamin B₁₂, iron, ferritin

• Biliary tract obstruction–bilirubin, cholesterol, enzymes and lipoprotein-X  

Note: Nonfunctional biochemical and immunologic markers of hepatic disease include those for hepatitides–HAV, HBV, HCV, HDV, HEV, and HIV, autoimmune diseases–anti-mitochondrial antibodies, PBC, malignancy–alpha-fetoprotein, relatively specific for liver cancer and metabolic diseases–ceruloplasmin in Wilson's disease, transferrin in hemochromatosis