[The Bavarian Thromboembolic Risk Cohort Study (BATER). Study protocol, state of the investigation and first results]

Familiar venous thromboembolic disease (VTE) is known to be related with factor V Leiden mutation (FVL), but also with other genetic markers. It is the objective to investigate of the BATER-study in a representative Bavarian cohort, and to assess whether they could predict VTE events. This paper shortly describes the study protocol, gives an overview of planned sub-studies, and provides first results of the historic cohort analysis.

The baseline survey of the cohort study of Bavarian women aged 18-49 years (random sample from the population) was performed in two samples in 1996 and 1997. It was planned to estimate a prevalence and predictive value of potential markers of VTE in a historic--prospective as well as concurrent approach with annual follow-up of the cohort. This representative cohort should build a basis for nested case-control studies and serve as a reference group for other analytical epidemiological studies in young women. 1685 women were ascertained (response rate 61%), underwent an inquiry, and provided blood samples for a blood bank; for this paper, complete data are available from 1650 women. Laboratory parameters were measured to determine APC resistance, FVL-mutation, antithrombin-, protein C and S deficiency, and were correlated to the results of a detailed, life-time history of thrombembolic events.

The prevalence of FVL mutation in the sample was 5.7% (95% confidence interval 4.6-6.6%). Other genetic VTE risk markers were observed to be less frequent than 1%. The positive predictive value (pPV) of FVL mutation for a VTE event is about 7%, but for a positive family history of VTE (first grade relatives) 3% only.

VTE events are rare in the German population of young women, even in cases of FVL mutation. A positive family history is rarely associated with the occurrence of VTE in women under 50 years of age, and the predictive value of FVL mutation is low. Therefore, a screening for FVL mutation is not justified unless there is suspicion of a high VTE risk for other reasons.