Optimizing Blood Collection and Storage Conditions for Soluble C-type Lectin-like Receptor 2 Measurement and Evaluating Diurnal Variation

抄録

　Platelets play a central role in hemostasis and thrombosis, with excessive activation contributing to thrombotic disease. While conventional activation markers such as platelet factor 4 (PF4), β-thromboglobulin (β-TG), and glycoprotein VI (GPVI) are measurable by ELISA, their utility is limited by pre-analytical variability associated with factors such as exercise, smoking, caffeine intake, and sample handling. Soluble C-type lectin-like receptor 2 (sCLEC-2) has recently been identified as a novel biomarker released upon platelet activation, although its stability and physiological variation have not been fully elucidated.

　sCLEC-2 was measured using an automated chemiluminescence immunoassay (STACIA^®). Blood from healthy volunteers into 3.2% sodium citrate (4.5 mL) and EDTA (2.0 mL) tubes was centrifuged to separate plasma and then stored in tubes at room temperature or 4 ℃ for up to 24 hours. The influence of residual platelets on sCLEC-2 levels was evaluated. Diurnal variation was assessed in healthy volunteers, and correlations with GPVI were analyzed in 29 patients with hematologic disorders.

　sCLEC-2 levels were 1.5-fold higher in EDTA samples than in citrate (p < 0.05). Immediately separated plasma remained stable for 24 hours, whereas storage in tubes led to time-dependent increases. Residual platelet counts above 1.0 × 10⁴/μL significantly elevated sCLEC-2. Morning sCLEC-2 levels were higher, consistent with the diurnal pattern of PAI-1. In hematologic disorders likely involving platelet activation, sCLEC-2 strongly correlated with GPVI (r = 0.809, p < 0.001). These findings demonstrate that sCLEC-2 is a sensitive and stable biomarker of platelet activation and provide practical recommendations for clinical sample handling.