Healthy Skepticism International News

July 2001

Hormone Replacement Therapy: Deep venous thrombosis and pulmonary embolism

Results:

56% of 1153 respondents indicated that the impact of HRT on increasing or decreasing the risk of deep venous thrombosis (DVT) and pulmonary embolism (PE) was very certain.

74% of 1153 respondents indicated that regarding DVT and PE, HRT was likely to be mildly harmful.

There was a significant negative correlation between respondent’s level of certainty and their estimate of benefit.  (Spearman’s rho = -0.32 p

<0.0001) Those who felt more certain were more likely to believe that HRT had a harmful effect on thromboembolism rates.

Our comment:

The impact of HRT on DVT and PE is probably known and is very harmful.

Explanation:

Again the HERS trial provides the best evidence that is relevant for Ann.[1]  In the HERS trial the rate of DVT plus PE was 0.87% in the placebo group vs 2.5% in the HRT group. (p = 0.004 ie the probability of this difference arising from chance alone is only 4 in 1,000).

Results from ERA trial and the Hemminki and McPherson study show trends for more thromboembolism but the numbers were too small to have the power to enable a statistical significant finding.  As mentioned above a trend for harm has been seen in the early results from the Womens’ Health Initiative trial also.

Four observational studies have found similar results with relative risks ranging from 2.1- 6.9 i.e. from twice as often to almost 7 times as often.[2]  Differences seen in any observational study may be due to confounding but the fact that RCT data are consistent increases confidence that the observed harm really is caused by HRT.

PE have very severe clinical consequences.

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