RESISTANCE TO ACTIVATED PROTEIN-C EVALUATED WITH APTT-BASED METHODS AND DNA ANALYSIS

Two approaches are at our disposal for the diagnosis of activated prot ein C (APC) resistance: 1) the semiquantitative plasma test based on a n aPTT assay and 2) the detection of the factor V gene defect by DNA a nalysis. In this work we evaluated sensitivity, specificity and diagno stic efficiency of the two plasma clotting tests at present available in Italy: Chromogenix and Behring, in 26 subjects found positive for A rg(506) --> Gln mutation and in 44 healthy subjects negative for the m utation, A sensitivity of 100% was never achieved; The Chromogenix tes t choosing 1.88 as ration threshold (corresponding to the mean ratio-2 SD), gave a specificity and a predictive positive value of 100%. The s ame accuracy indexes were achieved by the Behring test when a cut off of 1.43 (corresponding to the mean ratio-2SD) was used. Normalised rat ios for both tests yielded similar results. Therefor both test can be used as pre-screening tests in the diagnosis of APC resistance but gen otyping investigation is mandatory in the case of border line results.