RISK OF BIAS ASSESSMENT FOR STUDIES OF EXPOSURES

Abstract

When using evidence from non-randomized studies (NRS) to answer questions about the effects of environmental exposures on health, it is important to assess risk of bias (RoB) of individual studies as part of determining the certainty in the body of evidence. The recently released RoB in Non-randomized Studies of Interventions (ROBINS-I) instrument has undergone careful development and piloting on NRS of health interventions. A key feature of ROBINS-I is evaluating the RoB of studies against an ideal target trial, therefore establishing a structured comparison of RoB against a reference standard. While several instruments exist to evaluate the RoB of NRS of exposure, none of them use such a structured comparison of RoB. Using the fundamental design of ROBINS-I, we explored development of a version of the instrument to evaluate RoB in studies of environmental exposure. We identified important modifications necessitating a distinct instrument: The RoB instrument for NRS of exposures. This work highlights the importance of standardized methods for environmental health decision making, proposes a modified instrument to evaluate the RoB of NRS of exposures, provides guidance for the implementation of the instrument and integration into structured evidence-synthesis frameworks (such as GRADE [Grading of Recommendations Assessment, Development and Evaluation]), and presents evidence on the reliability and validity of the instrument. The RoB instrument for NRS of exposures delivers a standardized instrument that systematic review authors and guideline developers can use to evaluate RoB in NRS of exposures. The nature of these methodological changes allow better integration of RoB assessment in the environmental health field with GRADE.