Platelet Antibodies

Platelet Antibodies

Synonym/acronym: Antiplatelet antibody; platelet-bound IgG/IgM, direct and indirect.

Common use

To assess for the presence of platelet antibodies to assist in diagnosing thrombocytopenia related to autoimmune conditions and platelet transfusion compatibility issues.

Specimen

Serum (1 mL) collected in a red-top tube for indirect immunoglobulin G (IgG) antibody. Whole blood (7 mL) collected in a lavender (EDTA)-, yellow (ACD)-, or pink (K2EDTA)-top tube for direct antibody.

Normal findings

(Method: Solid-phase enzyme-linked immunoassay) Negative.

Description

Platelet antibodies can be formed by autoimmune response, or they can be acquired in reaction to transfusion products or medications. Platelet autoantibodies are immunoglobulins of autoimmune origin (i.e., immunoglobulin G [IgG]), and they are present in various autoimmune disorders, including thrombocytopenias. Platelet alloantibodies develop in patients who become sensitized to platelet antigens of transfused blood. As a result, destruction of both donor and native platelets occurs along with a shortened survival time of platelets in the transfusion recipient. The platelet antibody detection test is also used for platelet typing, which allows compatible platelets to be transfused to patients with disorders such as aplastic anemia and cancer. Platelet typing decreases the alloimmunization risk resulting from repeated transfusions from random donors. Platelet typing may also provide additional support for a diagnosis of post-transfusional purpura.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the detection of platelet alloimmune disorders
  • Determine platelet type for refractory patients

Potential diagnosis

Increased in

  • Development of platelet antibodies is associated with autoimmune conditions and medications.

  • AIDS (related to medications used therapeutically)
  • Acute myeloid leukemia (related to medications used therapeutically)
  • Idiopathic thrombocytopenic purpura (related to development of platelet-associated IgG antibodies)
  • Immune complex diseases
  • Multiple blood transfusions (related in most cases to sensitization to PLA1 antigens on donor red blood cells that will stimulate formation of antiplatelet antibodies)
  • Multiple myeloma (related to medications used therapeutically)
  • Neonatal immune thrombocytopenia (related to maternal platelet–associated antibodies directed against fetal platelets)
  • Paroxysmal hemoglobinuria
  • Rheumatoid arthritis (related to medications used therapeutically)
  • Systemic lupus erythematosus (related to medications used therapeutically)
  • Thrombocytopenias provoked by drugs (see monograph titled “Complete Blood Count, Platelet Count”)

Decreased in

    N/A

Critical findings

    N/A

Interfering factors

  • There are many drugs that may induce immune thrombocytopenia (production of antibodies that destroy platelets in response to the drugs). The most common include acetaminophen, gold salts, heparin (Type II HIT), oral diabetic medications, penicillin, quinidine, quinine, salicylates, sulfonamides, and sulfonylurea.
  • There are many drugs that may induce nonimmune thrombocytopenia (effect of the drug includes bone marrow suppression or nonimmune platelet destruction). The most common include anticancer medications (e.g., bleomycin), ethanol, heparin (Type I HIT), procarbazine, protamine, ristocetin, thiazide, and valproic acid.
  • Hemolyzed or clotted specimens will affect results.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating for issues related to platelet compatibility.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s hematopoietic and immune systems, especially any bleeding disorders and other symptoms, as well as results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including anticoagulants, aspirin and other salicylates, herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values). Note the last time and dose of medication taken.
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Note the patient’s response to platelet transfusions.
  • Instruct the patient to report severe bruising or bleeding from any areas of the skin or mucous membranes.
  • Recognize anxiety related to test results, and discuss the implications of abnormal test results on the patient’s lifestyle. Help patients who have a bleeding disorder understand the importance of taking precautions against bruising and bleeding. Provide education for precautions to include the use of a soft-bristle toothbrush, use of an electric razor, and avoidance of constipation, intramuscular injections, and acetylsalicylic acid (and similar products).
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include angiography abdominal, biopsy bone marrow, bleeding time, clot retraction, CBC platelet count, CT brain, Ham’s test, hemosiderin, and LAP.
  • Refer to the Hematopoietic and Immune systems tables at the end of the book for related tests by body system.
References in periodicals archive ?
Diagnosis Laboratory findings Disseminated intravascular Very high D-dimers; prolonged PT/PTT; coagulation (DIC) low fibrinogen Malignant hypertension No thrombocytopenia Heparin-induced thrombocytopenia No anemia or schistocytes Evans's syndrome Positive DAT; platelet antibodies Disseminated malignancy Pancytopenia; DIC features Table 2: vWF-CP activity and inhibitor findings in TTP and HUS.
Tests for antinuclear antibody (ANA) and platelet antibodies were negative.
Patients who have made platelet antibodies from transfusions or pregnancies can transfer these antibodies to their offspring during pregnancies, causing the problem of neonatal alloimmune thrombocytopenia (28).
Platelet aggregation caused by cold platelet antibodies is probably still the most common cause for the laboratory problems.
If the laboratory uses flow-cytometry-based platelet count with platelet antibodies (CD41 or CD61), the presence of RBC fragments would not affect platelet counts.
Because laboratory testing for heparin-induced platelet antibodies is readily available, an attempt is often made to rule out HIT prior to pursuing more elaborate assays for DIT in patients taking heparin in addition to other DIT-associated drugs (note that the algorithm presented in Figure 2 assumes prior laboratory/ clinical exclusion of HIT or that the patient has had no exposure to unfractionated or low molecular weight heparin).
More specific reference testing is available for drug-dependent platelet antibodies using enzyme immunoassay or flow cytometry technology.
Heparin-induced platelet antibodies were identified on the day after transfer; heparin was discontinued and lepirudin initiated.
Pseudothrombocytopenia: an immunologic study on platelet antibodies dependent on ethylene diamine tetra-acetate.
Platelet antibodies in Mrs Wood's blood meant she had difficulty creating blood clots - a condition similar to haemophilia.
Detection of platelet antibodies in chronic idiopathic thrombocytopenic purpura (ITP).
Although platelet-associated IgG levels are increased, no method of testing for platelet antibodies is specific for ITP.

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