A shortened activated partial thromboplastin time is associated with the risk of venous thromboembolism.
Hypercoagulability due to high coagulation factors XI, VIII, IX, II, and fibrinogen is recognized as a risk factor of venous thromboembolism (VTE). These factors are cumulatively explored by the activated partial thromboplastin time (APTT). To test the hypothesis that a short APTT increases the risk of VTE, a case-control study was carried out in 605 patients referred for thrombophilia testing after documented VTE and in 1290 controls. Median APTT ratio (coagulation time of test-to-reference plasma) values were 0.97 (range: 0.75-1.41) for patients and 1.00 (range: 0.72-1.33) for controls (P < .001). In patients who had an APTT ratio smaller than the fifth percentile of the distribution in controls, the odds ratio (OR) for VTE was 2.4 (95% confidence interval [CI]: 1.7-3.6) and was independent of inherited thrombophilic abnormalities. Further statistical analyses in 193 patients and 259 controls for whom factor VIII (FVIII) levels were available showed a decrease of the OR from 2.7 (95% CI: 1.4-5.3) to 2.1 (95% CI: 1.0-4.2), indicating that the risk was only partially mediated by high FVIII levels. In conclusion, hypercoagulability detected by a shortened APTT is independently associated with VTE. This inexpensive and simple test should be considered in the evaluation of the risk of VTE.
Tripodi
Armando
A
Angelo Bianchi Bonomi, Hemophilia and Thrombosis Center, Department of Internal Medicine, University and IRCCS Maggiore Hospital, Milano, Italy. armando.tripodi@unimi.it
Chantarangkul
Veena
V
Martinelli
Ida
I
Bucciarelli
Paolo
P
Mannucci
Pier Mannuccio
PM
D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D005169:Factor VIII / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010314:Partial Thromboplastin Time; D011237:Predictive Value of Tests; D012306:Risk; D013923:Thromboembolism / Q000097:blood*; D019851:Thrombophilia / Q000175:diagnosis*; D020246:Venous Thrombosis / Q000097:blood*
D005169:Factor VIII