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Estimating risk difference from relative association measures in meta-analysis can infrequently pose interpretational
Mohammad Hassan Murad1, Victor M Montori, Stephen D Walter
1The Knowledge and Encounter Research Unit, Mayo Clinic, Rochester, MN 55905, USA. murad.mohammad@mayo.edu
Journal of Clinical Epidemiology
|February 24, 2009
Summary
Estimating risk difference (RD) from relative measures in meta-analysis can yield counterintuitive results. Pooling RDs directly is often more appropriate, especially when baseline risks are similar.
Area of Science:
- Biostatistics
- Epidemiology
- Medical Meta-Analysis
Background:
- Risk difference (RD) is commonly estimated using relative association measures from meta-analyses and baseline risk.
- This method can present challenges, particularly when confidence intervals (CIs) for relative risk (RR) are non-significant.
Purpose of the Study:
- To describe a problematic situation in estimating RD from relative association measures.
- To investigate the occurrence of counterintuitive results when CIs of RR cross 1.0.
Main Methods:
- Examined a meta-analysis where RR CI overlapped 1.0, leading to contradictory RD interpretations.
- Calculated 10 different RDs from published meta-analyses using RR, odds ratio, and pooled RD methods.
Main Results:
- Counterintuitive RD interpretations occurred in 2 out of 10 instances when estimated from relative measures.
- This discordance arises from the logarithmic transformation of relative measures, causing asymmetric CIs.
Conclusions:
- Pooling RD across studies is a more appropriate method when relative association measures are non-significant and counterintuitive results arise.
- Direct pooling of RD is particularly valid when baseline risks across studies are homogeneous.
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