Panel 1.

Problems with systematic reviews of published prognostic studies (adapted from Altman 2001 ¹⁴ )

Difficulty of identifying all studies Negative (non‐significant) results may not be reported (publication bias) Inadequate reporting of methods Variation in study design Most studies are retrospective Variation in inclusion criteria Lack of recognised criteria for quality assessment Different assays or measurement techniques Variation in methods of analysis Differing methods of handling of continuous variables (some dependent on data) Different statistical methods of adjustment Adjustment for different sets of variables Inadequate reporting of quantitative information on outcome Variation in presentation of results (for example, survival at different time‐points)