The inherent bias in studies reporting outcomes using total opioid burden metrics:

Total opioid burden (OME/MME) is a widely used outcome, appearing in over 4,000 papers in five years, yet the conversion values behind it rest on a thin evidence base. Two simulation studies show that bias depends on the mix of opioids given and the error in the conversion values used, and an exploratory literature search finds that methods are poorly reported and difficult to reproduce. Studies should report mean doses for each opioid alongside the conversion values used.