Increased incidence of venous thrombosis in patients with shortened activated partial thromboplastin times and low ratios for activated protein C resistance.
A cohort of 69 hospital patients with shortened activated partial thromboplastin time (APTT) were prospectively identified and were further investigated for resistance to activated protein C (APC). This was quantified by APTT-based and Russel viper venom time (RVVT)-based methods. The prevalence of objectively confirmed venous thromboembolism (VTE) in this cohort was 19% (13/69). Of these 69 patients, 28 also had low APC resistance ratios and the incidence of VTE among these patients (group 1) was 36% (10/28). This was significantly higher (P=0.003) than that in the remaining 41 patients (group 2) with shortened APTT and normal APC resistance (7%, 3/41). DNA analysis confirmed 13 of the group 1 patients were FV Leiden positive. The incidence of VTE in the FV Leiden group (group 1a, n=13) was 38% (5/13) and in the group whose abnormal resistance to APC was independent of FV Leiden (group 1b, n=15) was 33% (5/15). These results suggest that a shortened APTT, coexisting with a low APC resistance ratio, regardless of FV Leiden carriership status, is a marker for VTE. Increased resistance to the anticoagulant activity of APC is multifactorial as reflected by evidence of abnormal resistance differing in the two assays.
Aboud
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MR
Department of Haematology, Royal North Shore Hospital, Sydney, Australia. maboud@doh.health.nsx.gov.au
Ma
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D020016:Activated Protein C Resistance / Q000150:complications*; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005165:Factor V; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011517:Prothrombin Time; D012307:Risk Factors; D013923:Thromboembolism / Q000097:blood / Q000209:etiology / Q000235:genetics; D020246:Venous Thrombosis / Q000097:blood* / Q000209:etiology / Q000235:genetics
C095381:factor V Leiden; D005165:Factor V