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We appreciate the comments of Drs Addiss and Davis and Mr Vaughn. We contend that if the clinician is interested in selective screening, then he or she needs to be able to estimate a patient's individual probability of infection to decide whether to test. Although our model's performance is less than ideal, advantages over previous attempts at risk stratification include better discrimination and the ability to stratify patients into multiple risk groups, and reliability verified by prospective validation.We support the work of these authors in developing a selective screening program. We agree that one must know the local prevalence of disease to use the model to estimate probability and that the thresholds of risk that should guide decision making and screening policy remain unknown. Eventually the development of credible thresholds and generalizable diagnostic models may lead to both more effective and less costly screening programs.
Johnson BA, Poses RM. A Diagnostic Model for Diagnosing Chlamydial Infection-Reply. JAMA. 1991;265(15):1952. doi:10.1001/jama.1991.03460150055019