Normal plasma inhibits HIT-1–mediated platelet activation more effectively than 5% albumin. (A-B) PEA test results are depicted as a percentage of the value obtained with undiluted HIT-1. Red and blue bars show results obtained with HH131 and RR131 FcγRIIa platelets, respectively. Results obtained with 5% albumin dilution are represented by the horizontal dotted (RR131 platelets) and solid (HH131 platelets) lines. Comparable results were obtained with plasma from 3 different normal individuals (normal plasma #1-#3). Means +1 standard deviation of triplicate determinations are presented and were compared by using the Student t test. P < .05 was considered significant. *P < .05; **P < .01; ***P < .001. ns, not significant.