Evaluating the consistency of heterogeneous results: important determinants of inconsistency

This poster presents analyses of study results for current asthma and pulmonary function endpoints performed as part of a systematic evaluation of the literature database on studies examining the potential for respiratory and immune-mediated conditions in relation to formaldehyde exposure that was conducted through October 2016. The consistency of results for current asthma was examined via forest plots presenting effect estimates (e.g., risk ratios, odds ratios) stratified by exposure levels (low vs high) and overall study confidence, and an analysis of potential confounding looking across study results was conducted for current asthma and pulmonary function endpoints.

Impact/Purpose

The analysis of study results across a set of studies is a powerful tool that can help with decisions about whether a potential bias is an important concern for an individual study, and to illuminate a pattern within apparently inconsistent effect estimates. The heterogeneity may stem from differing study designs examining varying outcome and exposure definitions and be influenced to varying degrees by sources of bias and other factors that affect the magnitude, direction, and precision of effect estimates. This type of analysis also can include factors, such as exposure levels, that are important for the interpretation of results. Studies of the association between indoor formaldehyde exposure and current asthma and pulmonary function were used as a case study to illustrate the impact of bias and other study attributes on the analysis of consistency across studies.

Citation

Glenn, B., E. Radke-Farabaugh, AND A. Kraft. Evaluating the consistency of heterogeneous results: important determinants of inconsistency. NAS Workshop on Evidence Integration in Chemical Assessments, Washington, District Of Columbia, June 03 - 04, 2019.