Platelet Antibodies, Serum

Immunity

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No Fasting Required

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Autoantibodies against platelets.

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Platelet Antibodies Serum - Comprehensive Medical Test Guide

Why is it done?
- Detects presence of antibodies against platelet antigens (HPA and HLA antibodies) in the bloodstream
- Evaluates immune-mediated platelet destruction and transfusion-related complications
- Diagnoses Post-Transfusion Purpura (PTP) when acute thrombocytopenia develops after transfusion
- Identifies Platelet Transfusion Refractoriness when patients fail to achieve expected platelet increment after transfusion
- Assists in managing Immune Thrombocytopenia (ITP) and Neonatal Alloimmunization
- Typically performed when patients experience unexplained thrombocytopenia or have received multiple transfusions
- Ordered prior to platelet transfusions in sensitized patients to select compatible blood products
Normal Range
- Negative Result: No platelet antibodies detected in serum (preferred outcome)
- Positive Result: Platelet antibodies present, with specific antigen specificity identification (HPA or HLA)
- Units of Measurement: Reported as presence/absence or with antibody titer levels (1:2 to 1:512+)
- Interpretation: Normal result indicates absence of alloimmunization and compatible platelet transfusion candidates; positive results suggest immune sensitization requiring special transfusion management
- Reference Range Notes: Most laboratories use qualitative testing (positive/negative); quantitative titers may increase with repeat transfusions or immune stimulation
Interpretation
- Negative Platelet Antibody Result: Indicates no alloimmunization; patient is appropriate candidate for random donor or single-donor platelet transfusions; no transfusion refractoriness due to immune cause
- Positive HPA (Human Platelet Antigen) Antibodies: Suggests alloimmunization from previous transfusions; requires HPA-typed platelet selection; may cause transfusion refractoriness; increased risk of Post-Transfusion Purpura
- Positive HLA (Human Leukocyte Antigen) Antibodies: Indicates HLA alloimmunization from prior transfusions or pregnancy; requires HLA-compatible or cross-matched platelet transfusions; common cause of immune-mediated platelet refractoriness
- Elevated Antibody Titers: Higher titers correlate with greater risk of transfusion reactions and refractoriness; may indicate recently sensitized patient or ongoing alloimmunization
- Factors Affecting Results: Number and frequency of transfusions; pregnancy history; recent transfusion timing; immunosuppressive therapy; presence of non-specific antibodies; hemolysis or lipemia in sample
- Post-Transfusion Purpura Pattern: Positive platelet antibodies with acute thrombocytopenia 3-10 days post-transfusion; typically HPA-1a antibodies; requires immediate specialized management
- Transfusion Refractoriness Pattern: Positive antibodies with failure to increment platelet count after transfusion; distinguishes immune from non-immune causes of refractoriness
Associated Organs
- Primary Organ System: Hematopoietic and lymphoid system; bone marrow (platelet production); immune system (antibody formation)
- Associated Conditions - Alloimmunization Disorders: Post-Transfusion Purpura; Immune Platelet Transfusion Refractoriness; HLA alloimmunization from transfusions or pregnancy; Neonatal Alloimmune Thrombocytopenia (NAIT)
- Associated Conditions - Hematologic Disorders: Immune Thrombocytopenia (ITP); Thrombotic Thrombocytopenic Purpura (TTP); Hemolytic Uremic Syndrome; Disseminated Intravascular Coagulation (DIC); acute leukemia requiring transfusion support
- Patient Populations at Risk: Heavily transfused patients (chronic anemia, cancer, surgery); multiparous women; solid organ or stem cell transplant recipients; patients on long-term dialysis
- Potential Complications: Severe thrombocytopenia with bleeding risk; transfusion reactions and refractoriness; reduced effectiveness of hemostatic support; increased mortality in transfusion-dependent patients
- Associated Diagnostic Challenges: Distinguishing immune from non-immune causes of platelet refractoriness; differentiating HPA from HLA antibodies; managing pregnancy complications related to maternal antibodies
Follow-up Tests
- HPA and HLA Antibody Specificity Testing: Identifies specific antigen targets for transfusion planning; determines which HPA or HLA types are compatible; improves transfusion strategy
- Platelet Crossmatching: Performed when patient has positive platelet antibodies; tests donor platelets against patient serum; ensures compatible transfusion product selection
- Platelet Count (CBC with Differential): Establishes baseline thrombocytopenia severity; monitors response to transfusion and treatment; evaluates transfusion refractoriness
- Posttransfusion Platelet Increment Study: Measures platelet count immediately before and 1 hour after transfusion; evaluates adequacy of response; identifies immune vs non-immune refractoriness
- HLA Typing: Determines patient's HLA type; enables selection of HLA-matched platelets for alloimmunized patients; reduces transfusion reactions
- Coagulation Studies (PT/INR, aPTT): Assesses bleeding risk from thrombocytopenia; evaluates global coagulation status; guides transfusion thresholds and additional blood product requirements
- Reticulocyte Count: Evaluates bone marrow response; distinguishes production vs consumption causes of thrombocytopenia; relevant in Post-Transfusion Purpura
- Peripheral Blood Smear: Examines platelet morphology and blood cell characteristics; identifies schistocytes in TTP; assesses for other coagulopathy indicators
- NAIT Panels (for neonatal cases): Maternal and neonatal HPA typing; maternal antibody testing; identifies antigen incompatibility in fetal alloimmune thrombocytopenia
- Monitoring Frequency: Repeat testing may be performed 2-4 weeks after initial transfusion if initial result unclear; monitoring with each transfusion episode in sensitized patients; annual screening for chronically transfused populations recommended by some centers
Fasting Required?
- Fasting Requirement: No fasting required
- Sample Collection: Serum sample collection via standard venipuncture in appropriate tube (typically serum separator or plain red-top tube)
- Specimen Handling: Allow sample to clot for 30-45 minutes at room temperature before centrifugation; handle gently to prevent hemolysis; refrigerate if testing delayed (do not freeze unless performing HPA/HLA specificity testing)
- Medications to Avoid: No medications need to be specifically avoided; patients may continue all regular medications including antiplatelet agents and anticoagulants
- Special Considerations: Specimen should be collected after transfusion event if evaluating Post-Transfusion Purpura; timing of 24-48 hours post-transfusion optimal for maximum antibody detection; inform laboratory of clinical indication for testing
- Quality Requirements: Avoid lipemic or hemolyzed samples that may interfere with testing; ensure adequate volume (typically 5-10 mL serum); label specimen clearly with patient identification and collection date/time
- Patient Preparation: No special preparation needed; patient may eat and drink normally; can be tested at any time of day; inform phlebotomist of recent transfusions for appropriate sample timing

How our test process works!