TECHNICAL REPORTSA 2-year retrospective analysis of laboratory testing for activated protein C resistance with a factor V-corrected activated partial thromboplastin time-based methodDe Bel, Annelies Va; Van der Cruyssen, Greta Ab; Devreese, Katrien MaAuthor Information aLaboratory of Clinical Biology bCenter for Medical Genetics, Ghent University Hospital, Ghent, Belgium Received 30 May, 2005 Revised 10 October, 2005 Accepted 24 October, 2005 Correspondence and requests for reprints to Katrien Devreese, Laboratory of Clinical Biology (2P8), Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium Tel: +32 9 240 65 67; fax: +32 9 240 49 85; e-mail: [email protected] Blood Coagulation & Fibrinolysis: March 2006 - Volume 17 - Issue 2 - p 155-160 doi: 10.1097/01.mbc.0000203861.47492.db Buy Metrics Abstract The factor V-corrected activated protein C resistance assay is the test of choice to screen for the factor V Leiden mutation. During the past 2 years, local test results with the frequently used Coatest APCR kit were evaluated and compared with the results of DNA analysis, the ‘gold standard’. Samples of 278 patients were analysed by both techniques. We were unable to confirm that factor V Leiden carriers can clearly be delineated from normal individuals with the Coatest APCR test. A ratio of 2.0 as the cut-off provides 99.0% sensitivity and 95.4% specificity. To evaluate the lupus anticoagulant interference, we retrospectively analysed 16 lupus anticoagulant-positive patients. In this study, two (12.5%) showed a false-positive activated protein C resistance result. Six out of 16 (37.5%) lupus anticoagulant-positive patients were also carriers of the factor V Leiden mutation. Four out of eight (50%) false-positive activated protein C resistance results presented with an abnormal baseline clotting time. In order to prevent reporting false-positive results, a maximum baseline clotting time (65.8 s) was calculated. A new scheme for interpreting activated protein C resistance ratios was proposed. © 2006 Lippincott Williams & Wilkins, Inc.