Antithrombin, Protein C, Protein S and Activated Protein C Resistance in the General Healthy Chinese Population: Normal Plasmatic Ranges and Genetic Defects.

Introduction: The inherited risk factors for venous thromboembolism differ between Caucasians and Chinese, antithrombin (AT), protein (PC) and protein (PS) deficiencies being the most common in Chinese patients. However, the age- and gender-related normal activity ranges of AT, PC, PS and the prevalence of their deficiencies in the general Chinese population remained to be determined.

Methods: 3493 healthy volunteers, 1759 women and 1734 men, blood donors or individuals taking routine health checkup, were recruited in four Chinese medical centers, Beijing, Tianjin, Shanghai and Suzhou, between February and May 2006. The inclusion criteria were: informed consent, normal renal and liver functions, no anticoagulant, contraceptive or hormonal substitutive therapy, no previous thrombosis. The plasma levels of AT, PC, PS activities and APC-R were measured with the same batches of reagents and the same type of analyzer (Stago). For the individuals with low activities, mutations of PROC gene, PROS1 gene or SERPINC1 gene were determined by direct sequencing analysis. Restriction fragment length polymorphism analysis was performed in those APC-R positive samples to detect 5 single nucleotide polymorphisms (SNPs) in FV gene, including R306T, R306G, R506Q, H1299R and I359T.

Results: The plasma activities (mean±SD) were: AT 109.4%±10.1%, PC 110.2%±20.4%, PS 95.4%±21.6% and APC-R 155sec±20sec. The normal ranges (mean±2SD) were: AT 89–130%, PC 69–151%, PS 52–139% and APC-R 114–195sec. Using multiple linear regression models, we identified significant (p<0.05) effects of age and gender on plasma activities and APC-R. Therefore, age- and gender- related normal ranges were further estimated by using the simplified parametric method. Gene analysis allowed identification of 15 individuals with nucleotide mutation: 3 in SERPINC1 gene, 10 in PROC gene and 2 in PROS1 gene. No recurrent gene mutation was found. Four PROC gene mutations, W41R, A121T, P247S and T315A, and two mutations of PROS1 gene, L216F and R314C, were novel. Based on the results of gene analysis, the estimated prevalence of inherited AT, PC and PS deficiency was 0.86 per 1000, 2.86 per 1000 and 0.57 per 1000, respectively. None of the 5 selected SNPs in FV gene was detected in APC-R positive subjects.

Conclusions: This is the largest population study ever conducted in China to determine the normal activity levels of the three main natural anticoagulants in the healthy population and their genetic deficiencies. The prevalence of the genetic deficiency of the three proteins was 4.3 per 1000. Contrary to previous studies in China and other Asian areas, PC deficiency was most frequent, followed by PS deficiency and AT deficiency. Six novel mutations were found and there was no recurrent mutation. It has been confirmed again that the common SNPs in FV gene responsible for APC-R in the Caucasians were not detectable in Chinese population. The normal plasmatic ranges according to age and gender should be considered when evaluating the thrombotic risk or events in the Chinese population.