Background
In case-control studies, elevated levels of interleukins 6 and 8 have been found to be associated with an increased risk of
venous thrombosis (VT). Because of the design of these studies, it remained uncertain whether these alterations were a cause or a result of the VT. In order to distinguish between the two, we set out to measure the levels of six
inflammatory markers prior to thrombosis in a
population-based
cohort using a nested case-cohort design.
Methods and Findings
Between August 1995 and June 1997, blood was collected from 66,140 people in the second Norwegian Health Study of Nord-Trndelag (HUNT2). We identified venous thrombotic events occurring between entry and 1 January 2002. By this date we had registered 506 cases with a first VT; an age- and sex-stratified random
sample of 1,464 controls without previous VT was drawn from the original cohort. Levels of interleukins 1, 6, 8, 10, 12p70, and tumour necrosis factor- were measured in the baseline sample that was taken 2 d to 75 mo before the event (median 33 mo). Cut-off points for levels were the 80th, 90th, and 95th percentile in the control group. With odds ratios ranging from 0.9 (95 CI: 0.61.5) to 1.1 (95 CI: 0.71.8), we did not find evidence for a relationship between VT and an
altered inflammatory profile.
Conclusions
The results from this population sample show that an altered inflammatory profile is more likely to be a result rather than a cause of VT, although short-term effects of transiently elevated levels cannot be ruled out.
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