Extending TTM-Based Quantitative Predictions to HIV Prevention Among MSM

Abstract

The purpose of this study was to extend the Testing Theory-based Quantitative Predictions approach (TTQP) using the transtheoretical model of behavior change (TTM) to condom use behavior in a sample of men who have sex with men (MSM). The TTQP approach employs the theory to generate effect size predictions, then the observed effect sizes can be calculated and compared to the predicted effect sizes. The effect size predictions in this study were made: 1) based on the omega squared reported in previous TTQP studies of other health behavior changes (e.g., smoking cessation); 2) based on theoretical considerations; and 3) calculated from the data reported in previous TTM condom use studies. The study design was a secondary analysis using data from a cross-sectional study. The final sample size was 185. However, the number of participants who were limited to membership in the first three stages (i.e., at-risk participants) was 85. The observed ω2 across the first three stages and their 90%, 95%, as well as 99% confidence intervals were calculated using SAS. Results demonstrated that when 90% CI was used, 4 of 10 predictions were confirmed for predictions based on previous TTQP studies of other health behavior changes, 8 of 17 predictions were confirmed for predictions based on theoretical considerations, and 13 of 16 predictions were confirmed for predictions based on previous TTM condom use studies; when 95% CI was used, 4 of 10 predictions were confirmed for predictions based on previous TTQP studies of other health behavior changes, 9 of 17 predictions were confirmed for predictions based on theoretical considerations, and 13 of 16 predictions were confirmed for predictions based on previous TTM condom use studies; when 99% CI was used, 6 of 10 predictions were confirmed for predictions based on previous TTQP studies of other health behavior changes, 14 of 17 predictions were confirmed for predictions based on theoretical considerations, and 15 of 16 predictions were confirmed for predictions based on previous TTM condom use studies. The explanations of failed predictions for this study included sample fluctuation (near misses), a need for prediction/theory revision, and a need for further recalibration of the effect size categories. Findings suggested that the first two prediction methods (i.e., predictions based on theoretical considerations and predictions based on previous TTQP studies of other health behavior changes) did not do well at predicting effect size estimates for MSM condom use behavior when 90% CI or