PEDIATRICS Vol. 123 No. 2 February 2009, pp. 437-444 (doi:10.1542/peds.2008-0488)
ARTICLE |
Performance of a Rapid Antigen-Detection Test and Throat Culture in Community Pediatric Offices: Implications for Management of Pharyngitis
a Department of Pediatrics, Children's Memorial Hospital and Northwestern University Feinberg School of Medicine, Chicago, Illinois
b Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio
c Infectious Diseases Laboratory, Children's Memorial Hospital, Chicago, Illinois
d MaryAnn and J.Milburn Smith Child Health Research Program, Children's Memorial Research Center, Chicago, Illinois
OBJECTIVES. The goals were to establish performance characteristics of a rapid antigen-detection test and blood agar plate culture performed and interpreted in community pediatric offices and to assess the effect of the pretest likelihood of group A streptococcus pharyngitis on test performance (spectrum bias).
METHODS. Two throat swabs were collected from 1848 children 3 to 18 years of age who were evaluated for acute pharyngitis between November 15, 2004, and May 15, 2005, in 6 community pediatric offices. One swab was used to perform the rapid antigen-detection test and a blood agar plate culture in the office and the other was sent to our laboratory for blood agar plate culture. Clinical findings were used to calculate the McIsaac score for each patient. The sensitivities of the office tests were calculated, with the hospital laboratory culture results as the criterion standard.
RESULTS. Thirty percent of laboratory blood agar plate cultures yielded group A streptococcus (range among sites: 21%–36%). Rapid antigen-detection test sensitivity was 70% (range: 61%–80%). Office culture sensitivity was significantly greater, 81% (range: 71%–91%). Rapid antigen-detection test specificity was 98% (range: 98%–99.5%), and office culture specificity was 97% (range: 94%–99%), a difference that was not statistically significant. The sensitivity of a combined approach using the rapid antigen-detection test and back-up office culture was 85%. Among patients with McIsaac scores of >2, rapid antigen-detection test sensitivity was 78%, office culture sensitivity was 87%, and combined approach sensitivity was 91%. Positive diagnostic test results were significantly associated with McIsaac scores of >2.
CONCLUSIONS. The sensitivity of the office culture was significantly greater than the sensitivity of the rapid antigen-detection test, but neither test was highly sensitive. The sensitivities of each diagnostic modality and the recommended combined approach were best among patients with greater pretest likelihood of group A streptococcus pharyngitis.
Key Words: pharyngitis rapid diagnostic tests throat culture group A Streptococcus
Abbreviations: BAP—blood agar plate GAS—group A streptococcus RADT—rapid antigen-detection test POL—physician office laboratory ARF—acute rheumatic fever CLIA—Clinical Laboratory Improvement Act CI—confidence interval
Accepted May 19, 2008.
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