Increased plasma levels of soluble CD40 ligand correlate with platelet activation markers and underline the need for standardized pre-analytical conditions

ObjectivesTo investigate whether sCD40L dosage might represent a useful tool to explore in vivo platelet function.Design and methodssCD40L and sP-selectin levels and light transmission aggregometry (LTA) were analyzed in 69 healthy donors. Immunoassays were performed on platelet-depleted citrate plasma samples. The effects of in vitro aspirin treatment on the release of sCD40L were investigated in 15 subjects following platelet stimulation. The effects of a 1-month therapeutic course of low-dose aspirin on sP-selectin and sCD40L levels were also investigated.ResultsA significant correlation was observed between sCD40L and sP-selectin (p < 0.01). In vitro aspirin treatment remarkably decreased sCD40L levels following platelet activation by exogenous agonists. sCD40L directly correlated with LTA (Rho = 0.62, p < 0.0001). In vivo aspirin treatment significantly reduced both sP-selectin and sCD40L levels (both p < 0.01) in a direct correlation (Rho = 0.66, p < 0.05).ConclusionsCitrated plasma samples reflect sCD40L released from platelets, thus yielding the most valid estimates of in vivo circulating levels of this platelet activation markers.