engleski

Analysis of factor VIII activity in patients referred for thrombophilia testing

Background Since persistently increased plasma level of factor VIII (FVIII) above 150% has been recognized as an independent risk factor for venous thromboembolism (VTE), FVIII should be included in thrombophilia testing. The aim of this study was to evaluate the results of FVIII activity in unselected consecutive patients referred for thrombophilia testing during a one year period (from January 2013 to December 2013). Methods FVIII activity was measured using one- stage APTT-based coagulometric method (Actin FS, FVIII deficient plasma, Siemens, Germany) on BCSXP analyzer (Siemens, Germany). Results FVIII assay was requested for a total of 129 patients as a part of thrombophilia testing with following clinical conditions: VTE=79, cardiovascular disease (CAD)=12, pregnancy=10, cerebrovascular insult (CVI)=8, miscarriage=8, infertility=6, epilepsy=2, hemiplegia=2, malignancy=2. A total of 38 patients had increased FVIII and 91 patients had FVIII level within reference range (70- 150%). Of the 38 subjects with increased FVIII, 21 had a single episode of VTE: deep venous thrombosis (DVT)=12 and pulmonary embolism (PE)=9. Frequency of increased FVIII among all VTE patients was 26.6% (21/79), meanSD age 4613.9 years, 11 males and 10 females, meanSD FVIII level 193.217.6%. FVIII values were no statistically different between patients with DVT (189.119.7%) and PE (199.013.4%), P=0.224. For all VTE patients FVIII was measured more than 3 months after VTE episode. Beside of VTE patients, there were 17 other patients with increased FVIII levels: pregnant women=7, CAD=3, CVI=2, hemiplegia=2, malignancy=2, epilepsy=1. Further, for a minority of patients with initial increased FVIII activity, i.e. for 2/38 or 5.3%, testing was repeated. Conclusion A significant number of VTE patients with increased FVIII activity suggests that thrombophilia testing should also include measurement of this coagulation factor. However, our results indicated that laboratory investigation of FVIII has not been completely performed in accordance with the recommended guidelines on testing related to key questions who and when to test. At first, for a large number of patients included in thrombophilia testing for other thrombophilic risk factors (data not presented), FVIII assay was not referred at all. It could be the reason of falsely higher proportion of VTE patients with increased FVIII levels. Second, FVIII was requested for 10 pregnant women, of which even 7 had increased FVIII activity. Since it is well known that FVIII levels are physiologically increased during pregnancy and puerperium, testing for FVIII as thrombophilic risk factor should be delayed for at least 6 weeks postpartum. Further, except for VTE patients, FVIII was requested as part of thrombophilia testing also in clinical conditions other than VTE. Finally, but not least, for a minority of VTE patients with an initial positive result for FVIII (>150%), testing was repeated after 3 to 6 months, in order to confirm a persistent constitutional increased FVIII over time and not due to an acute phase response. Based on the results in our patients population it is obvious that laboratory has to take more substantial role in the investigation process of FVIII as thrombophilic risk factor, pointing the importance of determining FVIII in accordance with the recommended guidelines related to the questions who and when to test, all in order to obtain accurate and reliable test result.

increased factor VIII; thrombophilia; risk factor; venous thromboembolism

Broj sažetka: P24 ; strana 57