Effects of a rapid antigen test for group A streptococcal pharyngitis on physician prescribing and antibiotic costs.

Decision analysis and opinion survey suggest that introduction of rapid antigen detection tests should decrease the number of patients with negative test results for group A streptococcal pharyngitis treated by antibiotics. We reviewed all cases in which a test for group A streptococcal pharyngitis was performed during the last 7 months of culture diagnosis and the first 7 months of antigen test diagnosis at an inner city community health center, recording culture or antigen test results, whether antibiotics were prescribed, and patient status (as regular health center patients or patients referred to the center). Positive rates for culture and antigen-test periods were similar (10% and 12%), but 53% of patients with negative culture were treated, where only 32% of patients with negative antigen-test results received prescriptions. Significant reductions in the treatment of patients with negative test results were found in both patient-status subpopulations: health center patients, 43% to 29%; referred patients, 91% to 52%. Among health center patients reductions were consistent for both adult (30% to 21%) and child and adolescent (55% to 45%) age groups. For all patients with negative test results, direct costs of diagnostic reagents and antibiotic prescriptions fell from $3.58 per patient with culture to $3.45 with antigen testing; the $0.13 savings per patient was due to less treatment of referred patients. Thus, rapid antigen testing led to (1) significantly fewer patients with negative test results receiving antibiotic prescriptions; and, (2) savings in antibiotic costs offsetting reagent cost of antigen detection diagnosis.