Fig. 2.

Detection of FXIa in plasma prepared from blood drawn into CTI. (A) Standard curves prepared from blood drawn into citrate or citrate + CTI as described in the legend for Fig. 1. A representative experiment out of two experiments where samples with or without CTI were compared directly is shown. (B) FXIa levels in PPP and PRP prepared from blood drawn into citrate + CTI, stimulated with thrombin or TF. Plasma samples from two healthy donors were stimulated by the indicated procoagulants, and FXIa concentration was determined using the FXIa–C1inh ELISA. The average lower limit of detection, defined as the concentration of FXIa that gives a signal 2-fold higher than the background, was 5.1 ± 0.1 pM for PPP and 5.2 ± 0.2 pM for PRP. BQL, below quantification limit.