Normalized APC sensitivity ratios in 337 patients with deep-vein thrombosis and 455 controls. None of these subjects carries the factor V Leiden mutation. The horizontal lines represent the median n-APC-SR (0.95 for patients and 1.01 for controls), the 95th percentile (P95; 1.14 for patients and 1.24 for controls), and the 10th percentile (P10; 0.83 for patients and 0.89 for controls).