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Spectrum bias of a rapid antigen detection test for group A beta-hemolytic streptococcal pharyngitis in a pediatric
Matthew C Hall1, Burney Kieke, Ralph Gonzales
1Marshfield Clinic Research Foundation, Marshfield, Wisconsin 54449, USA.
Insights
Rapid antigen detection testing (RADT) for group A beta-hemolytic streptococcal (GABHS) pharyngitis in children shows variable sensitivity based on disease severity. Culture confirmation is still recommended for all negative RADT results in pediatric patients.
Area of Science:
- Pediatric infectious diseases
- Diagnostic test performance evaluation
- Microbiology and immunology
Background:
- Rapid antigen detection testing (RADT) is widely used for diagnosing group A beta-hemolytic streptococcal (GABHS) pharyngitis in children.
- The accuracy of RADT, specifically its sensitivity, can be influenced by disease severity, a phenomenon known as spectrum bias, which has been observed in adult populations.
- Understanding spectrum bias in pediatric GABHS pharyngitis is crucial for determining the necessity of confirmatory throat cultures for all negative RADT results.
Purpose of the Study:
- To evaluate the effectiveness of a clinical scoring system in predicting GABHS pharyngitis in children.
- To investigate the presence and impact of RADT spectrum bias in pediatric patients diagnosed with GABHS pharyngitis.
- To assess whether RADT performance in children necessitates culture confirmation for all negative tests.
Main Methods:
- Retrospective review of laboratory and clinical records of pediatric patients undergoing RADT for suspected GABHS pharyngitis.
- Stratification of patients based on the modified Centor criteria (fever, absence of cough, pharyngeal exudates, cervical lymphadenopathy).
- Calculation of RADT sensitivity using positive RADT results and positive throat culture results for those with negative RADT.
Main Results:
- The overall prevalence of GABHS pharyngitis was 27%.
- RADT sensitivity varied significantly with disease severity, increasing from 47% in patients with 0 Centor criteria to 90% in those with 3 or 4 criteria.
- Spectrum bias was confirmed, with higher RADT sensitivity observed in children presenting with more severe symptoms.
Conclusions:
- The sensitivity of RADT for diagnosing GABHS pharyngitis in children is not constant and is dependent on the clinical severity of the infection.
- Even in pediatric cases with 3 or more Centor criteria, the sensitivity of RADT remains insufficiently high to reliably rule out GABHS pharyngitis without confirmatory throat cultures.
- These findings underscore the continued importance of throat cultures to confirm negative RADT results in children to ensure accurate diagnosis and appropriate treatment of GABHS pharyngitis.
Background:
Rapid antigen detection testing (RADT) is often performed for diagnosis of group A beta-hemolytic streptococcal (GABHS) pharyngitis among children. Among adults, the sensitivity of this test varies on the basis of disease severity (spectrum bias). A similar phenomenon may occur when this test is used in a pediatric population, which may affect the need for culture confirmation of all negative RADT results.
Objectives:
To assess the performance of a clinical scoring system and to determine whether RADT spectrum bias is present among children who are evaluated for GABHS pharyngitis.
Methods:
Laboratory and clinical records for a consecutive series of pediatric patients who underwent RADT at the Marshfield Clinic between January 2002 and March 2002 were reviewed retrospectively. Patients were stratified according to the number of clinical features present by using modified Centor criteria, ie, history of fever, absence of cough, presence of pharyngeal exudates, and cervical lymphadenopathy. The sensitivity of the RADT was defined as the number of patients with positive RADT results divided by the number of patients with either positive RADT results or negative RADT results but positive throat culture results.
Results:
RADT results were positive for 117 of 561 children (21%), and culture results were positive for 35 of 444 children (8%) with negative RADT results. The overall prevalence of GABHS pharyngitis was 27% (95% confidence interval: 23-31%). The prevalence of GABHS pharyngitis was 18% among patients with 0 Centor criteria, 16% among those with 1 criterion, 32% among those with 2 criteria, and 50% among those with 3 or 4 criteria. Spectrum bias was present, inasmuch as RADT sensitivity increased with Centor scores, ie, 47% sensitivity among children with 0 Centor criteria, 65% among those with 1 criterion, 82% among those with 2 criteria, and 90% among those with 3 or 4 criteria.
Conclusions:
The sensitivity of RADT for GABHS pharyngitis is not a fixed value but varies with the severity of disease. However, even among pediatric patients with > or =3 Centor criteria for GABHS pharyngitis, the sensitivity of RADT is still too low to support the use of RADT without culture confirmation of negative results.
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