Background: Medical thromboprophylaxis (MT) guidelines are poorly adhered to in practice. However, the guidelines have been criticised, and prophylaxis carries a risk of major haemorrhage. Non-adherence will cause the benefits of prophylaxis to be forfeited but the bleeding risk with anticoagulation will fall. The net effect has not been studied.
Methods: Using a validated spreadsheet model amended for non-adherence, I estimated the effect of non-adherence with MT guidelines on the annual Australian incidence of clinical deep venous thrombosis (DVT), pulmonary embolus (PE), fatal and non-fatal bleeds and fatal PE. The model gave estimates obtained with current UK, Australian (2) and US guidelines and a further guideline proposed by the author. Each guideline varies in the risk factors used to identify high-risk patients, and hence in their VTE risk. As in a previous study, the model was populated with the clinical event data reported in the PREVENT trial.
Findings: Non-adherence caused a proportionate increase in estimated VTE events including PE deaths compared to fully adherent prophylaxis, but this was offset by fewer major bleeds and fewer haemorrhagic deaths. A net reduction in mortality was present at all levels of non-adherence. The trends were most marked in guidelines with broad eligibility, as used in Australia and the UK. The high incidence of bleeding and case-fatality rates for bleeding and PE found in the PREVENT trial also contributed, but the net effect persisted when independent literature values were substituted.
Conclusion: The assumption that non-adherence with current MT guidelines will necessarily cause clinical detriment may be incorrect, especially in respect of guidelines that allow for broad eligibility.
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