When Systematic Reviews Disagree: How Should Clinicians Interpret the Evidence?

An Assumption That Research Always Converges

Systematic reviews are often treated as a final, settled word on a clinical question — yet it is not unusual for two separately published systematic reviews, addressing the very same clinical question, to arrive at meaningfully different or even directly contradictory conclusions.

Why Reviews of the Same Question Can Diverge

A detailed analysis of this problem identified several recurring causes of discordant systematic reviews: differences in which studies were included or excluded based on quality criteria, differences in the specific outcome measures and time points emphasised, differences in statistical methods used to pool results, and differing publication dates capturing different slices of an evolving evidence base (Jadad, Cook & Browman, 1997).

A Practical Approach When Reviews Conflict

Rather than simply picking whichever review supports a preferred approach, a more defensible response involves examining why the reviews differ — checking which included higher-quality primary studies, which used more clinically relevant outcome measures, and which is more recent and therefore likely to reflect the fuller, more current body of evidence.