Logistic regression models in obstetrics and gynecology literature

Objective: To evaluate the reporting of multivariable logistic regression a nalyses and assess variations in quality over time in the obstetrics and gy necology literature. Methods: Methodologic criteria for reporting logistic regression analyses w ere developed to identify problems affecting accuracy, precision, and inter pretation of this approach to multivariable statistical analysis. These cri teria were applied to 193 articles that reported multivariable logistic reg ression in the issues of four generic obstetrics and gynecology journals in 1985, 1990, and 1995. Rates of compliance with,the methodologic criteria a nd their time trends were analyzed. Results: The proportion of articles using logistic regression analysis incr eased over time: 1.7% in 1985, 2.8% in 1990, and 6.5% in 1995 (P < .001 for trend). Violations and omissions of methodologic criteria for reporting lo gistic models were common. The research question, in terms of dependent and independent variables, was not clearly reported in 32.1%. The process of v ariable selection was inadequately described in 51.8% of the articles. Amon g articles with ranked independent variables, 85.1% did not report assessme nt of conformity to linear gradient. Tests for goodness of fit were not giv en in 93.2% of articles. The contribution of the independent variables coul d not be evaluated in 36.2% of the articles because of a lack of coding of the variables. Interactions between variables were not assessed in 86.4% of articles. Analysis of variations in the quality of logistic regression ana lyses over time showed no increase in reporting of the criteria concerning variable selection and goodness of fit. However, the proportion of articles reporting one quality criterion concerning interpretation of the substanti ve significance of independent variables showed a trend toward improvement: 42.3% in 1985, 73.6% in 1990, and 75.4% in 1995 (P = .004 for trend). Conclusion: The reporting of multivariable logistic regression models in th e obstetrics and gynecology literature is poor, and the time; trends of imp rovement in quality of reporting are not particularly encouraging. (Obstet Gynecol 1999;93:1014-20. (C) 1999 by The American College of Obstetricians and Gynecologists.).