Evaluating the impact of a home screening test for streptococcal pharyngitis.

Home screening tests must be evaluated as an aid to self-referral to a physician and should not be judged as if they were diagnostic procedures, i.e. the sole determinants of a therapeutic decision. The performance characteristics of a test are properly compared to those of the patient or parent, operating in the absence of the test. For streptococcal pharyngitis there would be a net increase in the number of cases correctly treated whenever the sensitivity of the home test (multiplied by the probability that the patient will act upon the test results) exceeds the a priori probability that the patient will be seen by a physician in the absence of the test. Use of home screening tests is likely to increase the number of patient-physician contacts among persons with sore throats and will do so proportionately more frequently among those with streptococcal pharyngitis.