| Platelet aggregation testing in thrombocytopenic patients Cathy Hayward. |
Abstract
Background: Light transmission aggregometry (LTA) is important for diagnosing platelet function disorders (PFD) and forms of von Willebrand disease (VWD) affecting ristocetin-induced platelet aggregation (RIPA). Nonetheless, data is lacking on the utility of LTA for investigating thrombocytopenic patients and platelet rich plasma samples with low platelet counts (L-PRP). Previously, we developed a strategy for diagnostic LTA assessment of L-PRP that included: 1) acceptance of referrals/samples, regardless of thrombocytopenia severity; 2) tailored agonist selection, based on which are informative for L-PRP with mildly or severely low platelet counts, and 3) interpretation of maximal aggregation (MA) using regression-derived 95% confidence intervals, determined for diluted control L-PRP (C-L-PRP).
Methods: To further evaluate the L-PRP LTA strategy, we evaluated findings for a subsequent cohort of patients.
Results: Between 2008-2021, the L-PRP strategy was applied to 211/1810 (11.7%) consecutive diagnostic L-PRP aggregation tests for 192 unique patients (platelet counts X 10e9 /L, as median [range] for blood and L-PRP: 105 [13-282], 164 [17-249], respectively). Patient-L-PRP had more abnormal MA findings than C-L-PRP (p-values < 0.001). Among patients with accessible electronic medical records (n=181), L-PRP LTA uncovered significant aggregation abnormalities in 45 (24.9%), including 19/31(61.3%) with <80 X 10e9 platelets/L L-PRP, and it ruled out PFD, and VWD affecting RIPA, in others. The L-PRP LTA strategy helped diagnose type 2B and suspected platelet-type VWD disease, Bernard Soulier syndrome, familial platelet disorder with myeloid malignancy, suspected ITGA2B/ITGB3-related thrombocytopenia, and acquired PFD.
Conclusion: Diagnostic LTA with L-PRP, using a strategy that considers thrombocytopenia severity, is feasible and informative.
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