Peter Thomas, PhD, MPH¹, Harold A. Pollack, PhD², Matthew L. Boulton, MD, MPH³, Julie Horrocks, PhD⁴, Rosemary Rochford, PhD¹, and Sherman A. James, PhD⁵. (1) School of Public Health, Department of Epidemiology, The University of Michigan, 109 Observatory St., Rm 1009 SPH I, Ann Arbor, MI 48109-2029, 404 272-0173, petert@umich.edu, (2) Health Management and Policy, University of Michigan School of Public Health, 109 Observatory, SPH II, Ann Arbor, MI 48109-2029, (3) Bureau of Epidemiology, Michigan Department of Community Health, 3423 N. Martin Luther King Jr. Blvd, Lansing, MI 48909, (4) Center For Statistical Consultation and Research, The University of Michigan, 3514 Rackham Building, Ann arbor, MI 48109-1070, (5) School of Public Health, University of Michigan, 1420 Washington Heights, Ann Arbor, MI 48109-2029

Background: Chlamydia trachomatis is the most common and costly of the bacterial sexually transmitted diseases, costing the US about $2.4 billion annually. Research suggests selective screening by age is the best predictor of infection. An alternative is to screen all clinic patients. Objective: To evaluate the cost-effectiveness of chlamydia screening comparing three screening options: 1) Selective screening based on age 2) Universal screening and 3) Not screening any clients for infection. Methods: Using decision analysis models from a healthcare delivery perspective, we enlisted different prevalence and clinic type scenarios, to calculate cost of each method, cost of screening per client, cost to cure, and incremental cost-effectiveness ratios (ICER), the additional cost for one strategy to prevent one more infection than another strategy. Sequelae cost was a weighted cost of complications and sequelae using published information on costs and probabilities of infection, disease, and treatment. Results: Selective screening by age was marginally a better choice in populations having moderate chlamydia prevalence rates, (4% –7%). Universal screening was more cost-effective in high prevalence groups (7% – 24%). Not screening at all would be more cost-effective for managing chlamydia infections in a very low prevalence area (<2%). Conclusion: In Michigan, screening only those persons <25 years of age is more cost-effective than screening persons <20 in lower prevalence areas. Given the small variation in ICERs and the cost of medical expenses, if the cost or cost value of an infection exceeds $500 then a preference for universal screening is more likely the better choice.

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