PROS1 and venous thromboembolism: As shown in Figure 1, the OR of venous thromboembolism in individuals with protein S deficiency based on free protein S tests was 8.9 (95% CI = 3.8–20.9, P < 0.001), and 7.6 (95% CI = 2.6–21.7, P < 0.001) in individuals with protein S deficiency based on PROS1 gene mutations.