 Materials and Methods Collection of blood samples Blood samples of 240 healthy children will be obtained from the blood that will be collected for the routine coagulation screening in neonates and in children 18 months or at the time of surgery in children aged 18 months. Healthy neonates will be recruited by the neonatologists. Children aged from 1 month to 15 years will be included by anesthesiologists before minor elective surgery such as tonsillectomy, adenoidectomy, phimosis or oral surgery. Additionally, blood from adults referred for thrombophilia testing will be studied. This study was approved by French authorities ANSM and CPP. Inform consent will be obtained from all participants. Blood will be collected into plastic tubes containing sodium citrate 0.106 M, tubes from Starstedt. Platelet poor plasma will be obtained by two centrifugations for 10 minutes at 2500 g at room temperature and stored at - 70C until further examination. 