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.

2518 Background: Although delta-granule platelet storage pool deficiencies (δ-PSPDs) are common disorders of platelet function, they are relatively poorly studied and described. One unknown is the relationship between δ-PSPDs and the PFA-100, a screening test originally developed for von Willebrand's disease but now widely used as a general screening test for coagulopathies. Previous studies have suggested that the PFA-100 is less effective in detecting mild platelet function disorders (which include δ-PSPDs) than more severe platelet function disorders. These studies, however, were limited by small numbers of patients with a variety of different platelet function defects. We examined PFA-100 results in a larger pediatric patient population diagnosed specifically with δ-PSPD, and determined the relationship between PFA-100 results and platelet electron microscopy (the standard for diagnosis of δ-PSPDs). Methods: This study is a retrospective medical record review of patients 0 to 18 years of age diagnosed with δ-PSPD at Nationwide Children's Hospital between January 1, 2008 and July 31, 2010. We defined δ-PSPD as patients with an average of fewer than 3.68 delta granules per platelet. We obtained demographic data including age, sex, and family history of bleeding. Lab data was also extracted, including PFA-100 and platelet electron microscopy. We determined the percentage of δ-PSPD patients with an abnormal PFA-100. To examine the correlation between the PFA-100 results and the average number of granules per platelet we used Spearman's Rho as our non-parametric measure of dependence. Results: A total of 88 patients diagnosed with δ-PSPD were included in this study. Of our patient population, 35% were male, and 61% had a first degree family history of easy bruising or bleeding, while only 15% had a family history that was positive specifically for platelet function disorders. The most common symptoms on presentation were easy bruising (56%), epistaxis (39%), oral cavity bleeding (35%) and menorrhagia (30%). Eighty-one of these patients underwent PFA-100 testing, of which 41% had an abnormal CEPI value, 17% had an abnormal CADP value, and 14% had abnormal results for both PFA cartridges. We found no statistical correlation between CEPI closure time and the average number of granules per platelet (rho = 0.0315, p value = 0.7798), nor between CADP closure time and the average number of granules (rho = -0.0095, p value = 0.9328)(Figure). Additionally, the number of bleeding symptoms in each patient was not statistically correlated with CEPI closure times, CADP closure times or platelet EM. Discussion: The PFA-100, which is widely used as a screening test for suspected bleeding disorders, was abnormal in fewer than half of pediatric patients diagnosed with δ-PSPD. We found that PFA-100 results did not correlate with presence or severity of delta-granule platelet storage pool deficiencies as determined by platelet electron microscopy. When evaluating patients with suspected bleeding disorders, PFA-100 testing alone cannot be used to rule out the presence of a δ-PSPD. Disclosures: No relevant conflicts of interest to declare.