M Bruce Edmonson1, Kathryn R Farwell. 1. Division of General Pediatrics and Adolescent Medicine, Department of Pediatrics, University of Wisconsin Medical School, Madison, Wisconsin, USA. mbedmons@wisc.edu
Abstract
OBJECTIVE: The sensitivity of a rapid antigen-detection test (RADT) for group A streptococcal (GAS) pharyngitis is critical to whether the test is cost-effective and to whether a confirmatory throat culture is needed. We evaluated a second-generation RADT to determine if its sensitivity varies across the broad clinical spectrum of patients tested for GAS in pediatric outpatient practice. METHODS: We used laboratory logbooks from a single pediatric clinic to identify 1184 consecutive patient visits at which an RADT was performed. In a blinded chart review, we calculated McIsaac scores to separately estimate the pretest clinical likelihood of GAS pharyngitis for visits at which the RADT result was positive (n = 384) and for visits at which the result proved to be false-negative (n = 65). Positive RADT results were assumed to be true positives, and test sensitivity was estimated by dividing the number of positive results by the sum of positives and false-negatives. RESULTS: As the clinical likelihood of GAS increased, there were stepwise increases in RADT sensitivity (from 0.67 to 0.88). Sensitivity was low (0.73; 95% confidence interval [CI]: 0.62-0.86) in patients clinically unlikely to have GAS (McIsaac score < or =2) and high (0.94; 95% CI: 0.89-0.99) in patients <15 years old who had tonsillar exudate and no cough. False-negative RADT results were associated with lighter growth of GAS than found on specimens obtained from a random sample of clinic patients who had only primary throat cultures ordered. CONCLUSIONS: For pediatric patients who are clinically unlikely to have GAS pharyngitis, as indicated by a McIsaac score < or =2, the sensitivity of a second-generation RADT may drop below thresholds reported for cost-effectiveness. For children who have tonsillar exudate and no cough, the test may be sensitive enough to meet current pediatric practice guidelines for stand-alone testing.
OBJECTIVE: The sensitivity of a rapid antigen-detection test (RADT) for group A streptococcal (GAS) pharyngitis is critical to whether the test is cost-effective and to whether a confirmatory throat culture is needed. We evaluated a second-generation RADT to determine if its sensitivity varies across the broad clinical spectrum of patients tested for GAS in pediatric outpatient practice. METHODS: We used laboratory logbooks from a single pediatric clinic to identify 1184 consecutive patient visits at which an RADT was performed. In a blinded chart review, we calculated McIsaac scores to separately estimate the pretest clinical likelihood of GAS pharyngitis for visits at which the RADT result was positive (n = 384) and for visits at which the result proved to be false-negative (n = 65). Positive RADT results were assumed to be true positives, and test sensitivity was estimated by dividing the number of positive results by the sum of positives and false-negatives. RESULTS: As the clinical likelihood of GAS increased, there were stepwise increases in RADT sensitivity (from 0.67 to 0.88). Sensitivity was low (0.73; 95% confidence interval [CI]: 0.62-0.86) in patients clinically unlikely to have GAS (McIsaac score < or =2) and high (0.94; 95% CI: 0.89-0.99) in patients <15 years old who had tonsillar exudate and no cough. False-negative RADT results were associated with lighter growth of GAS than found on specimens obtained from a random sample of clinic patients who had only primary throat cultures ordered. CONCLUSIONS: For pediatric patients who are clinically unlikely to have GAS pharyngitis, as indicated by a McIsaac score < or =2, the sensitivity of a second-generation RADT may drop below thresholds reported for cost-effectiveness. For children who have tonsillar exudate and no cough, the test may be sensitive enough to meet current pediatric practice guidelines for stand-alone testing.
Authors: Carolina Giraldez-Garcia; Beltran Rubio; Jose F Gallegos-Braun; Iñaki Imaz; Jesus Gonzalez-Enriquez; Antonio Sarria-Santamera Journal: Eur J Pediatr Date: 2011-02-11 Impact factor: 3.183
Authors: J F Cohen; M Chalumeau; C Levy; P Bidet; M Benani; M Koskas; E Bingen; R Cohen Journal: Eur J Clin Microbiol Infect Dis Date: 2013-01-23 Impact factor: 3.267
Authors: A Nissinen; P Strandén; R Myllys; J Takkinen; Y Björkman; P Leinikki; A Siitonen Journal: Eur J Clin Microbiol Infect Dis Date: 2008-07-05 Impact factor: 3.267
Authors: Emily H Stewart; Brian Davis; B Lee Clemans-Taylor; Benjamin Littenberg; Carlos A Estrada; Robert M Centor Journal: PLoS One Date: 2014-11-04 Impact factor: 3.240