Platelet transfusion refractoriness is the failure to achieve the desired level of blood platelets in a patient following a platelet transfusion. The cause of refractoriness may be either immune or nonimmune based. Among immune-related refractoriness, antibodies against HLA antigens are the primary cause. Non-immune causes include splenomegaly (enlargement of the spleen), fever, and recent chemotherapy.
Diagnosis
Platelet transfusion refractoriness is typically diagnosed using the corrected count increment, which requires 4 items of information:
- Pre-transfusion platelet count
- Post-transfusion platelet count: the post-transfusion blood sample for this measurement should be collected 10–60 minutes after the transfusion has been completed
- Body surface area
- Number of platelets transfused: the blood bank maintains records of the estimated number of platelets in each unit. Current requirements in the US stipulate that a unit of apheresis platelets must contain at least 3.0 x1011 platelets.
The CCI is calculated as follows: CCI= (Post-transfusion platelet count - Pre-transfusion platelet count)(BSA) ÷ (number of platelets transfused).
A CCI greater than 7500 indicates a sufficient post-transfusion increment, whereas a CCI less than 7500 is considered diagnostic of platelet refractoriness.
Immune-mediated refractoriness usually shows little or no increment in the immediate post-transfusion platelet count. Non-immune refractoriness may show an initial rise in platelet count, but a subsequent 8-hour or 12-hour post-transfusion sample shows a return to the baseline platelet count.