title: Female gender and resistance to activated protein C (FV:Q506) as potential risk factors for thrombosis after elective hip arthroplasty.
abstract: Resistance to activated protein C (APC) caused by the R506Q mutation in factor V is the most common inherited risk factor for venous thrombosis. To elucidate whether APC-resistance is a risk factor for venous thrombosis after elective total hip replacement, the association between APC-resistance (presence of FV:Q506 allele) and postoperative thrombosis was investigated in patients (n = 198) randomised to received short (during hospitalisation, n = 100) or prolonged prophylaxis (three weeks after hospitalisation, n = 98) with low molecular weight heparin (LMWH). Among APC-resistant individuals receiving short prophylaxis, 7/10 developed thrombosis as compared to 2/12 receiving long prophylaxis (p <0.0179). Odds ratio for association between APC-resistance and thrombosis in the short prophylaxis group was 4.2 (CI 95% 1.02-17.5) (p <0.0465). Among those receiving prolonged prophylaxis, there was no increased incidence of thrombosis associated with APC-resistance. Two unexpected observations were made. One was that APC-resistance was much more common in women (19/109) than in men (3/89) (p <0.001). The other was that even women without APC-resistance were much more thrombosis-prone than men. Thus, 24/48 of women with normal FV genotype and short prophylaxis developed thrombosis vs 8/42 among men, p = 0.002. The increased risk of thrombosis associated with female gender and APC-resistance was neutralised by the prolonged treatment. In conclusion, among patients receiving short prophylaxis, female gender was found to be a strong risk factor for venous thrombosis. Even though APC-resistance appeared to be a risk factor for postoperative thrombosis, the uneven distribution of APC-resistance between men and women, taken together with the increased risk of thrombosis among women, precluded valid conclusions to be drawn about the association between APC-resistance and an increased risk of thrombosis. Our results suggest that prolonged prophylaxis with LMWH after hip surgery is more important for women than for men.
authors.affiliation: Department of Hematology and Coagulation Disorders, University of Lund, University Hospital in Malmö, Sweden.
authors.forename: P J
authors.initials: PJ
authors.lastname: Svensson
authors.forename: G
authors.initials: G
authors.lastname: Benoni
authors.forename: H
authors.initials: H
authors.lastname: Fredin
authors.forename: O
authors.initials: O
authors.lastname: Björgell
authors.forename: P
authors.initials: P
authors.lastname: Nilsson
authors.forename: U
authors.initials: U
authors.lastname: Hedlund
authors.forename: G
authors.initials: G
authors.lastname: Nylander
authors.forename: D
authors.initials: D
authors.lastname: Bergqvist
authors.forename: B
authors.initials: B
authors.lastname: Dahlbäck
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D004351:Drug Resistance / Q000235:genetics; D005165:Factor V / Q000235:genetics*; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011486:Protein C / Q000502:physiology*; D012307:Risk Factors; D012727:Sex Characteristics; D013924:Thrombophlebitis / Q000209:etiology*
chemical_list: D011486:Protein C; D005165:Factor V