Diagnosis:
Platelet refractoriness
• Platelet refractoriness is a common issue and may be due to immune or nonimmune causes.
• Nonimmune causes include fever, sepsis, antibiotics, disseminated intravascular coagulation, and splenomegaly.
• Patients receiving multiple red blood cell or platelet transfusions may develop anti–class I human leukocyte antigen (HLA) antibodies, anti-platelet antibodies, or a combination of both.
• A corrected count increment (CCI) calculated using a 1-hour posttransfusion platelet count of less than 5,000 platelets× m2/μL indicates a likely immune cause of refractoriness.
• The CCI is calculated using the following formula: CCI = [body surface area (m2) × (post platelet count – pre platelet count) × 1011]/number of platelets transfused.
• A platelet antibody screen will detect the presence of anti–class I (HLA) antibodies, anti-platelet antibodies, or a combination of both.
• The patient’s plasma is mixed with a panel of platelets to determine reactivity.
• Anti–class I HLA antibody reactivity is destroyed with chloroquine.
• Depending on the antibody specificity seen, HLA-matched platelets or crossmatched platelets may be used.
• Some institutions will do a trial of ABO-matched platelets as platelets express ABH antigens and an improvement in the posttransfusion increment may be seen.
