Centrifugation Speed Affects Light Transmission Aggregometry

Background: Light transmission aggregometry (LTA) is considered the gold standard for investigating platelet activity ex vivo. However, LTA protocols are not standardized, and differences in LTA procedure are a potential source of variance in results. Centrifugation speed is an essential component of platelet preparation in LTA, has yet to be standardized, and may affect platelet aggregation results. We sought to investigate the effect of relative centrifugal force (RCF) intensity on LTA results.Methods: Ten healthy controls had venous blood drawn and centrifuged at 150, 200, 300, and 500 g for 10 min. Cell counts in whole blood and platelet-rich plasma (PRP) were measured using a hematology analyzer. LTA was performed using 1.0 mu m adenosine diphosphate (ADP) and 0.4 mu m epinephrine as an agonist. Aggregation (%) was compared at 60, 120, 180, and 300 s and at maximum aggregation.Results: Centrifugation speed was associated with decreasing platelet count (P < 0.001) and decreasing mean platelet volume (P < 0.001) in PRP. Maximum aggregation decreased with increasing speeds for ADP 1.0 mu m (150 g - 89%, 200 g - 93%, 300 g - 71%, 500 g - 17%; P < 0.001). Similar findings were noted at 120 s (150 g - 69%, 200 g - 50%, 300 g - 35%, 500 g - 12%; P < 0.001), 180 s (150 g - 82%, 200 g - 74%, 300 g - 44%, 500 g - 13%; P < 0.001), and 300 s (150 g - 85%, 200 g - 88%, 300 g - 55%, 500 g - 14%; P < 0.001). Consistently, platelet aggregation in response to epinephrine 0.4 lm decreased significantly with increasing centrifuge RCF at 60, 120, 180, 300 s and at maximum aggregation (P < 0.05 for each comparison).Conclusion: Our data demonstrate the importance of centrifugation speed in the interpretation of LTA results, supporting the need for standardization of centrifugation RCF in LTA protocols.