Experience with the rapid directigen test for influenza

Objective: To determine the sensitivity and positive predictive value of the Becton-Dickson Directigen AB performed on-site in a nursing home compared to viral culture. Setting: A 721-bed skilled nursing facility for veterans and spouses. Design measurements: Nasopharyngeal specimens were obtained with a low clinical threshold from residents during 3 influenza seasons for rapid antigen testing in the nursing home. The specimens were then transported for viral culture by courier on ice to a laboratory 45 miles away. Results: A total of 327 samples were obtained; 36 were positive for influenza A by rapid test, and all but 2 grew the organism on tissue culture with a positive predictive value of 94%. Nineteen specimens were negative by rapid test, but grew influenza A on tissue culture with a sensitivity of 64%. Influenza prophylaxis was usually initiated the day the first positive rapid test was encountered when influenza was active in the community. Conclusion: The Directigen AB is a reliable indicator of influenza when influenza has been culture-confirmed in the community. Although sensitivity is limited, a group of rapid tests provided early laboratory confirmation and facilitated the application of prophylaxis.