title: Is APC resistance a risk factor for venous thromboembolism in patients over 70 years?
abstract: Activated protein C (APC) resistance is the most common risk factor for venous thromboembolism (VTE). Previous studies mostly analysed patients under 70 years and reported a four- to sevenfold increased risk. This case-control study included consecutive patients referred for a clinical suspicion VTE to our medical unit: 621 patients with a well-documented diagnosis (cases) and 406 patients for which the diagnosis was ruled out and who had no personal history of VTE (controls). APC resistance related to factor V Leiden was defined by either a positive DNA analysis or a positive STA(R) Staclot APC-R assay. Under 70 years, APC resistance was associated with a threefold increased risk of VTE (odds ratio 3.2, 95% CI, 1.7 to 6.0), whereas in patients over 70 years, it appeared to be no longer a strong risk factor (odds ratio 0.8, 95% CI, 0.4 to 1.7). Age appeared as an effect-measure modifier with a significant interaction (p = 0.005). Our data suggest that APC resistance is not a risk factor for VTE in elderly.
mesh_terms: D020016:Activated Protein C Resistance / Q000150:complications* / Q000175:diagnosis; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016022:Case-Control Studies; D005165:Factor V; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013923:Thromboembolism / Q000209:etiology*; D020246:Venous Thrombosis / Q000209:etiology*
chemical_list: C095381:factor V Leiden; D005165:Factor V