The increment in platelets following platelet product transfusion is directly related to dose given, unless there is increased removal of the transfused platelets. The Corrected Count Index (CCI) is intended to differentiate between immune and nonimmune loss, with a post-transfusion specimen collected 1 hour after the platelet product transfusion. With immune thrombocytopenia there is little increment in the platelet count seen at 1 hour, whereas with nonimmune mechanisms the platelet count at 1 hour is relatively normal.
corrected count index (or CCI) =
= (((post-transfusion platelet count 1 hour after transfusion) - (pretransfusion count)) * (body surface area in square meters) * 10^11) / (total number of platelets transfused) =
= (((post-transfusion platelet count 1 hour after transfusion) - (pretransfusion platelet count)) * (body surface area in square meters) * (10^11)) / ((number of donor units transfused) * (platelets per unit))
where:
• The minimum number of platelets in a random single donor nonpheresis platelet concentrate is (5.5 * 10^10).
• The total number of platelets transfused = (number of products transfused) * (average number of platelets per product).
Interpretation:
• After transfusion of a single random platelet unit an increase of 5,000 - 10,000 platelets/µL can be expected in hemostatically stable adult with a body surface area of 1.8 meters squared.
• If the CCI is greater than 10,000, then antiplatelet antibodies are unlikely.
• If the CCI is less than 5,000, then antiplatelet antibodies are more likely.
Additional Testing:
• If there is evidence of immune destruction of platelets, then testing for antiplatelet antibodies is warranted.
• If there is evidence that antibodies to HLA are involved, then HLA-matched platelet products can be ordered.
• If there is no evidence of HLA-related antibodies, then the added expense for HLA-matched products is not considered warranted.
