A nested approach to evaluating dose-response and trend

PURPOSE: Conventional dose-response and trend analysis fits either a linear or categorical logistic model and tests the resulting coefficients. These analyses, however, are based an implausible assumptions. METHODS: We present an alternative approach that uses likelihood ratio tests to compare nested regression models and determine when a model is rich enough to capture the data trends. RESULTS: For illustration, we apply this approach to data on diet and colorectal polyps. CONCLUSIONS: Comparison of linear and quadratic spline logistic models indicates that the conventional approach of using only a linear logistic model would not appropriately describe the association between intake of fruits and vegetables and colorectal polyps in our data. Graphical checking further supports this conclusion. (C) 1991 by Elsevier Science Inc.