Evaluation of suspected urinary tract infection in ambulatory women: a cost-utility analysis of office-based strategies.

BACKGROUND The purpose of this study was to determine the most cost-effective strategy for managing suspected urinary tract infections in otherwise healthy adult women presenting to their primary care physician with dysuria and no symptoms or signs of pyelonephritis. Several office-based management strategies are considered: empiric therapy, use of dipstick analysis, use of complete urinalysis, and several strategies using office or laboratory cultures. METHODS We constructed a decision tree using model probabilities obtained from the literature. Where published probabilities were unavailable, we used extensive sensitivity analyses. Utilities were obtained from the Index of Well-Being. We obtained costs by surveying hospitals, physicians, and pharmacies. RESULTS The most cost-effective strategy is to treat empirically ($71.52 per quality-adjusted life month, QALM). When the cost of antibiotics exceeds $74.50 or if the prior probability of having a UTI is under 0.30, then treatment guided by the results of a complete urinalysis is preferred. While it was the preferred strategy, other strategies (complete urinalysis, culture and treat, and dipstick testing only) were associated with greater utility. The marginal cost-effectiveness of these strategies compared with empiric therapy ranged from $2964 to $48,460 per additional QALM. CONCLUSIONS The preferred strategy of empiric therapy is robust over a wide range of sensitivity analyses. While empiric therapy is associated with the best cost-utility ratio, doing a culture yields the greatest utility at greater incremental cost per QALM. Many primary care physicians already treat UTIs empirically with antibiotics. This study confirms that empiric therapy, while frowned upon by some, is a cost-effective strategy. Other strategies may be considered, but at greater marginal cost. Ultimately these findings need to be confirmed in clinical trials.