ObjectiveTo study the correlation between international normalized ratio (INR) and coagulation factor Ⅱ and Ⅹ in patients with pulmonary thromboembolism treated with warfarin at moderate and low intensity anticoagulation.MethodsFifty-one patients with pulmonary thromboembolism treated with warfarin orally were divided into low-intensity anticoagulation group (INR from 1.6 to 2.0) and standard-intensity anticoagulation group (INR form 2.0 to 3.0) according to their monitoring INR indices. The levels of coagulation factor Ⅱ and Ⅹ were measured, and the correlation between INR level and coagulation factor activity was compared.ResultsThe INR of the low intensity anticoagulation group was 1.69±0.2 and the standard intensity anticoagulation group was 2.55±0.46. The corresponding activity of coagulation factor Ⅱ was (48.3±28.0)% and (24.0±8.0)% respectively. The activity of coagulation factor Ⅹ was (32.8±24.0)% and (16.7±6.0)%. There was a negative correlation between the activity of INR and coagulation factor Ⅱ and Ⅹ, with correlation coefficients of –0.903 and –0.459, respectively. Coagulation factor Ⅱ activity < 40%, coagulation factor Ⅹ activity inhibitory level < 25% is defined as anticoagulation effect. When coagulation factor Ⅱ activity level reaches anticoagulation effect, the corresponding minimum INR value was 1.56 and as to coagulation factor Ⅹ, the corresponding minimum INR value was 1.66.ConclusionsINR is negatively correlated with the activity of coagulation factor Ⅱ and coagulation factor Ⅹ. With the increase of INR, the activity of coagulation factor Ⅱ and coagulation factor Ⅹ decrease. Low intensity anticoagulation could not effectively inhibit the activity of coagulation factor.