212 - Evaluation of two functional assay in detection of factor V Leiden carriers
Autor(s): S. Valverde, E. Trabuio, F. Antico, F. Manoni, G. Gessoni
Issue: RIMeL - IJLaM, Vol. 5, N. 3, 2009 (MAF Servizi srl ed.)
Page(s): 212-6
Summary
Background. In Clinical Pathology Laboratories the approach to diagnosis of Factor V Leiden is based upon functional tests that allowed the relevation of an activated protein C resistance (APCr) phenotype by using a PTT based assay. In this study the authors evaluated efficiency of two functional assays in comparison with to genetic diagnosis. Materials and Methods. We considered 292 patients after an episode of deep venous thrombosis. These subjects were evaluated by using routine protocol adopted in our Laboratory. Moreover all these samples were tested by using beside the routine PTT based assay, with a new PT based test for revelation of APCr. Results. Among the considered 292 patients the genetic study identified 124 (42.5%) FVL carriers: 111 heterozygous and 13 homozygotes. In discrimination between normal subjects and FVL carrier the aPTT based assay had a SE 1.00 and SP of 0.99, in discrimination between homozygous the performance was less satisfactory (SE=0.93, SP=0.96). In discrimination between normal subjects and FVL carrier the PT based assay had a SE 1.00 and SP of 1.00, in discrimination between homozygous the performance also very good (SE=1.00, SP=0.99). Conclusions. The PTT based test showed a satisfactory analytical performance to discriminate normal subjects from FVL carriers but are less useful to discriminate between heterozygous and homozygous patients. In our experience the PT based APC assay provides improved discrimination between normal subjects and FVL carriers compared with classical PTT based methods, moreover this assay allowed a good discrimination between homozygous and heterozygous FVL patients. Key-words. Thrombophilia, Factor V Leiden, APC resistance, Functional tests.