Use of a High-Sensitivity Rapid Strep Test Without Culture Confirmation of Negative Results

Third, suppurative complications of pharyngitis are a great deal more common than nonsuppurative complications. Prevention of these complications might better serve as the rationale for culture confirmation of negative antigen tests were it not for the fact that most of these infections typically occur in young adults, a population in which group A streptococcal pharyngitis is relatively uncommon, and are typically polymicrobial in origin, with anaerobic organisms commonly identified.^27-30

Although cultures of the abscessed fluid were not routinely performed on patients reviewed in our study, there is circumstantial evidence that bacteria other than GABHS may have been responsible for many of the suppurative complications seen. In this study, 23 patients with a suppurative complication had undergone a previous test for GABHS, only 26% of which were positive (25% by culture, 27% by high-sensitivity antigen test). Given the high sensitivity that we have previously demonstrated with both culture and the STREP A OIA,¹⁹ this finding is more readily explained by the presence of other abscess-causing bacteria than by false-negative GABHS test results. There were also 27 patients included in this study with a suppurative complication despite concurrent use of an antibiotic that would be expected to effectively treat GABHS. Although poor compliance may be the explanation for the observed treatment failure, this finding may also have been due to infection with other bacteria that were less responsive to these agents. Finally, culture was performed on 3 of the abscesses reviewed in this study, and all 3 grew species other than GABHS. Therefore, because species other than GABHS are most commonly responsible for suppurative complications of pharyngitis, it seems unlikely that the use of diagnostic strategies designed to identify the presence of GABHS—whether streptococcal antigen tests, cultures, or both—have much chance of preventing these complications.

Conclusions

This study recounts our 2-year experience using a high-sensitivity GABHS antigen test without culture confirmation of the negative results and compares it with 2 years of culture-only experience. Using this strategy, we did not see an increase in either suppurative or nonsuppurative complication rates, as had been feared by the AHA and the AAP. Our study demonstrates that streptococcus testing by culture and antigen detection are of equal value in the prevention of suppurative and nonsuppurative complications of pharyngitis.

Selection of the appropriate diagnostic test should be based on other factors, such as patient satisfaction, cost-effectiveness, improved work flow, and so forth. Although not specifically studied in this cohort, use of the high-sensitivity rapid test has already been associated with more appropriate use of antibiotics when managing patients with pharyngitis at the Lahey Clinic.¹⁹ Use of a high-sensitivity antigen test may also offer the additional advantage of immediate diagnosis, improved treatment rates, more rapid clinical improvement and return to normal activities, and reduced spread of GABHS infections.

Acknowledgments

Dr Webb is the Medical Director at BioStar, Inc, the manufacturer of the STREP A OIA antigen test. He received salary support during the performance of this study. Drs Needham and Kurtz received no financial support.