Platelet Antibodies

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

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

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

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

Critical Findings and Potential Interventions
N/A

Overview

(Study type: Blood collected in a red-top tube for indirect immunoglobulin G [IgG] antibody. Whole blood collected in a lavender- [EDTA], yellow- [ACD], or pink- [K2EDTA]-top tube for direct antibody; related body system: Circulatory/Hematopoietic and Immune systems.) 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.

Indications

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

Interfering Factors

Factors that may alter the results of the study

  • There are many drugs and other substances 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 and other substances 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.

Other Considerations:

  • Hemolyzed or clotted specimens will affect results.

Potential Medical Diagnosis: Clinical Significance of Results

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

Decreased In:
N/A

Nursing Implications

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Inform the patient this test can assist in evaluating for issues related to platelet compatibility.
  • Explain that a blood sample is needed for the test.

Potential Nursing Actions

  • Observe for symptoms of altered coagulation such as bruising, bleeding gums, or blood in urine, sputum, or stool.

Safety Considerations

  • Bleeding precautions may be necessary if there is a known or suspected coagulation problem.

After the Study: Potential Nursing Actions

Treatment Considerations

  • Note the patient's response to ordered platelet transfusions.
  • Explain to those with a bleeding disorder the importance of taking precautions against bruising and bleeding.
  • Instruct the patient to report severe bruising or bleeding from any areas of the skin or mucous membranes.
  • Provide education for bleeding precautions, including the use of a soft-bristle toothbrush, electric razor; and avoidance of constipation, intramuscular injections, and acetylsalicylic acid (and similar products).

Followup Evaluation and Desired Outcomes

  • Acknowledges that 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 including referral to another health-care provider.

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