A History of Abnormal Bleeding Correlates with Platelet Dysfunction in Aggregation Studies but Not PFA-100 Analyses

Introduction:In this retrospective medical records-based study we analyzed the association between abnormal spontaneous or procedure-related bleeding and patterns of abnormality in tests of platelet function. Commonly used platelet function tests include Platelet Function Analyzer -100 Closure Times (PFA-100 CT), platelet aggregation testing using Light Transmission Aggregometry (LTA), and platelet dense granule release assay (by lumi-aggregometry). Other related tests include Von Willebrand factor (VWF) analysis, platelet flow-cytometry for cell surface glycoprotein expression, and electron microscopy. LTA in our center uses five different agonists - ADP, arachidonic acid, collagen, epinephrine and ristocetin, while lumi-aggregometry is performed using four agonists - ADP, arachidonic acid, collagen and epinephrine.

Methods:This study included 497 patients who had platelet aggregation testing done using LTA between August 2008 and August 2013. Sixty-nine percent (n = 354) of these patients had a history of abnormal bleeding. Since the data were not normally distributed, Wilcoxon rank-sum test (for continuous variables) and Fisher's exact test (for categorical variables) were used wherever appropriate. P value of < 0.05 was considered as significant.

Results:Of the patients with a history of abnormal bleeding, 81% had spontaneous bleeding, 29% had surgery/procedure-related bleeding, and 13% had history of both types of abnormal bleeding. Three hundred nine of these patients had a recent (< 4 weeks) bleeding event. Abnormal bleeding, recent or historical, was found to associate significantly with impaired platelet aggregation, as well as platelet release in response to ADP, arachidonic acid, collagen or epinephrine (P<0.001 for all). Abnormal aggregation and release in response to ≥2 different agonists was also significantly associated with abnormal bleeding, as was the total number of abnormalities on the aggregation and release panel (P<0.001).

A history of a recent bleeding event (<4 weeks) was found to be associated with reduced aggregation in response to arachidonic acid (P = 0.001), impaired aggregation and release in response to collagen (P =0.04 and <0.001 respectively), and reduced platelet release in response to epinephrine (P = 0.005). Recent bleeding also correlated with the total number of abnormalities in the aggregation (P = 0.002) and release panels (p =0.03).

No significant association was found between a history of abnormal bleeding (either recent or historical) and prolonged PFA-100 closure times (collagen/ADP or collagen/epinephrine), or any abnormality in VWF analyses or platelet flow-cytometry studies.

Conclusions:While PFA-100 closure times, VWF analyses and platelet flow-cytometry panel failed to show an association with abnormal bleeding (historical or recent), impaired platelet aggregation or release in response to several agonists was found to correlate with abnormal spontaneous and/or procedure-related bleeding, recent as well as historical, suggesting that platelet aggregation and release assays may be useful in diagnosis of a bleeding diathesis in patients with an appropriate clinical history