Associations between studies using histologic specimens (versus other types of specimens) and the presence of each study-design feature, by multivariate logistic regression analysis. Odds ratios <1.0 indicate that the study-design feature was less common in studies using histologic specimens, whereas odds ratios >1.0 indicate that the study-design feature was more common in studies of histologic specimens. Error bars are 95% confidence limits. Odds ratios were based on models that also included disease (RA versus other), journal, the number of patients, data on animals, and category of biomarker as independent variables. Separate models were estimated for each study-design feature. Each model fit the data well (all Hosmer-Lemeshow test, P > 0.09).