Diagnosis and management of adults with pharyngitis. A cost-effectiveness analysis.

BACKGROUND: Rheumatic fever has become uncommon in the United States while rapid diagnostic test technology for streptococcal antigens has improved. However, little is known about the effectiveness or cost-effectiveness of various strategies for managing pharyngitis caused by group A beta-hemolytic streptococcus (GAS) in U.S. adults.
OBJECTIVE: To examine the cost-effectiveness of several diagnostic and management strategies for patients with suspected GAS pharyngitis.
DESIGN: Cost-effectiveness analysis. DATA SOURCES: Published literature, including systematic reviews where possible. When costs were not available in the literature, we estimated them from our institution and Medicare charges. TARGET POPULATION: Adults in the general U.S. population. TIME HORIZON: 1 year. PERSPECTIVE: Societal.
INTERVENTIONS: Five strategies for the management of adult patients with pharyngitis: 1) observation without testing or treatment, 2) empirical treatment with penicillin, 3) throat culture using a two-plate selective culture technique, 4) optical immunoassay (OIA) followed by culture to confirm negative OIA test results, or 5) OIA alone. OUTCOME MEASURES: Cost per lost quality-adjusted life-days (converted to life-years where appropriate) and incremental cost-effectiveness. RESULTS OF BASE-CASE ANALYSIS: Empirical treatment was the least effective strategy at a GAS pharyngitis prevalence of 10% (resulting in 0.41 lost quality-adjusted life-day). Although the other four strategies had similar effectiveness (all resulted in about 0.27 lost quality-adjusted life-day), culture was the least expensive strategy. RESULTS OF SENSITIVITY ANALYSES: Results were sensitive to the prevalence of GAS pharyngitis: OIA followed by culture was most effective when GAS pharyngitis prevalence was greater than 20%. Observation was least expensive when prevalence was less than 6%, and empirical treatment was least expensive when prevalence was greater than 71%. The effectiveness of strategies was also very sensitive to the probability of anaphylaxis: When the probability of anaphylaxis was about half the baseline probability, OIA/culture was most effective; when the probability was 1.6 times that of baseline, observation was most effective. Only at an OIA cost less than half of baseline did the OIA alone strategy become less expensive than culture. Results were not sensitive to other variations in probabilities or costs of diagnosis or treatment of GAS pharyngitis.
CONCLUSIONS: Observation, culture, and two rapid antigen test strategies for diagnostic testing and treatment of suspected GAS pharyngitis in adults have very similar effectiveness and costs, although culture is the least expensive and most effective strategy when the GAS pharyngitis prevalence is 10%. Empirical treatment was not the most effective or least expensive strategy at any prevalence of GAS pharyngitis in adults, although it may be reasonable for individual patients at very high risk for GAS pharyngitis as assessed by a clinical decision rule.