Comparison of light transmission aggregometry in patients with bleeding disorder of unknown cause and healthy blood donors.

Background: Light transmission aggregometry (LTA) plays an important role in the detection of platelet function disorders. Objectives: This study compared different agonist concentrations to detect patients with bleeding disorder of unknown cause (BDUC) with healthy blood donors. Methods: We retrospectively evaluated LTA performed in patients with BDUC and compared the results with prospectively collected LTA measurements from healthy blood donors. LTA was assessed with 2 μM, 5 μM, and 20 μM adenine diphosphate (ADP) in both groups; 1.0 mM arachidonic acid (AA) and 5 μM epinephrine in persons with BDUC; 1.0 mM and 1.5 mM AA and 5 μM and 10μM epinephrine in healthy blood donors. Results: After induction with 2 μM ADP, 43.8% of persons with BDUC and 24.3% of the healthy blood donors had abnormal maximum aggregation, but only 5.8% and 4.6% after induction with 5 μM ADP, respectively. Persons with BDUC had a higher proportion of abnormal maximum aggregation after induction with 1 mM AA (18.5%) compared to healthy donors (3.6%). No difference was observed after epinephrine induction. The sensitivity of an abnormal International Society on Thrombosis and Haemostasis Bleeding Assessment Tool score to predict an abnormal LTA was <22% and the negative predictive value >70%. Conclusion: This study reveals a high proportion of abnormal LTA results in persons with BDUC and healthy blood donors after induction with low concentrations of ADP and AA. The recommendations for those concentrations in guidelines for platelet function testing should be reassessed.