Methodological quality in medical evidence, quo vadis?

Efforts in research quality have led to a diffusion of publication guidelines for high-quality reporting of medical evidence with the aim to instill transparency to its evaluation. The maturity of this process has led to a second stage in which a surplus of scales measuring methodological quality is in place. However, there is no clear consensus as to which of these guidelines should be recommended for usage and how to integrate the methodological quality information into the evidence synthesis process. One major challenge that these scales poses is the fact that slight modifications performed to them in order to adapt to a specific research and/or management question requires revalidation of the scale's properties, a clearly impractical endeavor. This article proposes a potential alternative to this challenge through the formulation of a framework in which quality elements are divided into tiers. This layering aims at separating quality constructs that should be uniformly present across all studies and thus could be validated from constructs that are question-specific and less likely to undergo a formal validation process. An example of this framework applied to the urological literature is presented.