Respiratory syncytial virus (RSV) test positivity is dependent on characteristics of the patients for whom the tests are ordered, according to results published in BMC Infectious Diseases. Phuong T. Tran, BSPharm, MPH, and colleagues examined RSV testing practices and test positivity across private health insurance enrollees in the United States. They found that most tests were ordered for young children (age, 0-4; 65.8%) and in outpatient encounters (78.3%). Test positivity differed based on age (0-4, 19.8%; 5-17, 1.8%; adults, 0.7%), region (7.6% to 16.1%), and clinical setting (inpatient, 4.7%; outpatient, 14.2%). When compared with age, setting, or indication-specific positivity, bias due to using national surveillance systems positivity to correct for untested acute respiratory infections ranged from −76% to 3,556%. “Demographic-specific detail on testing practice and positivity can improve the accuracy of RSV incidence estimates,” Tran and colleagues wrote.