The PFA‐100® does not predict delta‐granule platelet storage pool deficiencies

Summary.  There are no published reports investigating the ability of the platelet function analyzer (PFA‐100^®) to detect the presence of delta‐granule platelet storage pool deficiencies (δ‐PSPD), a common mild bleeding disorder. Prior studies of the PFA‐100^® and congenital platelet disorders have been limited by small numbers of patients with a variety of disorders. We examined PFA‐100^® results in a large paediatric patient population diagnosed specifically with δ‐PSPD, and determined the relationship between PFA‐100^® and platelet electron microscopy (the gold standard for diagnosis). This study is a retrospective review of patients <19 years of age diagnosed with δ‐PSPD at Nationwide Children’s Hospital from 2008 to 2010. To examine the correlation between PFA‐100^® and average number of granules per platelet we used Spearman’s Rho as a non‐parametric measure of dependence. A total of 105 patients diagnosed with δ‐PSPD were included, of which 99 patients underwent PFA‐100^® testing. Of those tested 46% had at least one abnormal closure time, whereas 16% had abnormal results for both cartridges. We found no statistical correlation between C‐EPI closure time and average number of granules per platelet (ρ= ?0.0095, P‐value = 0.9328), nor between C‐ADP closure time and the average number of granules (ρ = 0.0315, P‐value = 0.7798). The PFA‐100^®, a widely used screening test for suspected bleeding disorders, did not correlate with presence or severity of δ‐PSPD as determined by platelet electron microscopy. When evaluating patients with suspected bleeding disorders, PFA‐100^® alone cannot be used to rule out the presence of a δ‐PSPD.