Diagnosis of mild platelet function disorders. Reliability and usefulness of light transmission platelet aggregation and serotonin secretion assays

P>Light transmission platelet aggregation (PA), adapted to measure platelet secretion (PS), is the reference test for diagnosing platelet functional disorders (PFD). Problems with these assays include lack of standardisation, unknown reproducibility and lack of universally accepted diagnostic criteria. We addressed these issues in patients with inherited mucocutaneous bleeding (MCB). Normal and abnormal PA tests in 213 patients were reproducible in 93 center dot 3% and 90 center dot 4% of the cases, respectively. Mean intra-subject coefficient of variation for PA with strong agonists were < 9% and mean intra-class correlation coefficient for weak agonists were > 0 center dot 86 (P < 0 center dot 0001). Concomitant impaired PA with 10 mu mol/l-adrenaline and 4 mu mol/l-ADP was observed in 13 center dot 7% of the controls. This combination was not considered per se a criterion for PFD. PA with adrenaline >= 42% or irreversible aggregation with 4 mu mol/l ADP had 93% and 95% Negative Predictive Value for diagnosing PFD, respectively. PA defects were consistently associated with abnormal PS. In contrast, 14 center dot 3% of patients with MCB had isolated PS. Thus, standardized PA/PS assays are highly reproducible and concordant in normal and patient populations. Normal PA with adrenaline and low ADP concentration robustly predict a normal PA. Simultaneous PA/PS assays enable the diagnosis of isolated PS defects. This study confirmed that hereditary PA-PS defects are highly prevalent.