May 31st, 2011

Biomarkers: Don’t Believe the Hype

Watch out for hype when examining the biomarker literature, a new study published in JAMA suggests. John Ioannidis and Orestis Panagiotou first searched the literature and identified highly cited studies of biomarkers that included a relative risk calculation of effect size on a particular outcome. Most of the 35 studies reported cancer- or cardiovascular-related outcomes. They then performed a second search to find subsequent meta-analyses on the same biomarker and outcome.

The investigators then compared the effect size of the first study with the subsequent meta-analyses. For 30 of the 35 studies, the effect size reported in the largest study included in the meta-analysis was smaller than the effect size reported in the original highly cited study. In a comparison of the original study with the entire meta-analysis, the same pattern was observed, with 29 of the 35 meta-analyses reporting a smaller effect size.

The authors conclude that before a biomarker is accepted there should be “extensive replication and validation of proposed biomarkers in large independent studies and assessment of their incremental ability.”

In an accompanying editorial, Patrick Bossuyt writes that the analysis “should convince clinicians and researchers to be careful to match personal hope with professional skepticism, to apply critical appraisal of study design and close scrutiny of findings where indicated, and to be aware of the findings of well-conducted systematic reviews and meta-analyses when evaluating the evidence on biomarkers.”

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