Diagnostic value of rapid antigen detection test for streptococcal pharyngitis in a pediatric population

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Summary

Acute upper respiratory tract infections in children may result in overuse of antibiotics as throat culture cannot be performed in every setting and results cannot be obtained early. A rapid and reliable test might decrease unnecessary antibiotic usage. The purpose of this study was to determine the prevalence of group A beta-hemolytic Streptococcus (GABHS) infections in different pediatric age groups and to assess the diagnostic value of rapid antigen detection test (RADT) for streptococcal pharyngitis. This study was performed in a pediatric outpatient clinic. All children who were admitted with signs and symptoms of acute upper respiratory tract infections were included in the study. Throat culture and RADT were performed and prevalence of GABHS was assessed. Diagnostic value of RADT was determined. This study included 1248 children with a mean age of 6.3 ± 3.6 years. There were 655, 518, and 75 children in age groups of 0–6, 7–12 and 13+ years, respectively. The overall prevalence of GABHS was 38.1% (475/1248), as judged by throat culture. The prevalence was highest in the 7–12-year age group (53.9%) and lowest in the 0–6-year age group (25.2%). Considering all patients, RADT gave a sensitivity of 89.7%, specificity of 97.2%. The sensitivity and specificity of RADT were similar in different age groups (p values >0.05). Diagnostic value of RADT is high and can be used safely in populations where streptococcal pharyngitis and its complications such as acute rheumatic fever and acute glomerulonephritis are common.

Introduction

Acute pharyngotonsillitis is the most common clinical presentation of group A beta-hemolytic Streptococcus (GABHS). Complications including otitis media, sinusitis, peritonsillar abscess, and suppurative cervical adenitis may develop in untreated patients. These acute problems, together with the nonsuppurative sequelae (i.e., acute rheumatic fever and acute glomerulonephritis) increase the clinical significance of GABHS. Prevalence of GABHS during school outbreaks of pharyngitis is between 15% and 50% in healthy school-age children [1]. Since toddlers with GABHS respiratory tract infection may not present with classical symptoms, the diagnosis of GABHS pharyngitis among children should be based on laboratory tests in conjunction with the clinical findings [1], [2]. Culture isolation of GABHS from the pharynx is the gold standard method, but 2 days are needed for it to be informative. On the other hand, the rapid antigen detection test (RADT) detects the presence of GABHS within a few minutes and has high sensitivity and specificity [3], [4]. Rapid testing has many additional benefits: early treatment within 48 h provides symptomatic relief for the child and limits spreading of the organism [5], [6], [7]. Besides, it allows the practitioner to treat only those cases with GABHS thus avoiding prescribing antibiotics for viral infections [7].

In Turkey, unnecessary antibiotic use is very common mainly because either microbiologic evaluation of the culture cannot be performed in primary health care units or the physicians do not want to wait for culture results where it is available [8]. A test which gives rapid and reliable results might decrease unnecessary antibiotic usage in our population. In this study, it was aimed to assess the validity of RADT for the diagnosis of streptococcal pharyngitis in an outpatient clinic with a relatively large number of children stratified by age to determine the prevalence of streptococcal pharyngitis in this population.

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Materials and methods

This study was performed in a pediatric outpatient clinic between January 1998 and December 2001. All children who were admitted with signs and symptoms of acute upper respiratory tract infections were included in the study. Patients were examined by the same pediatrician and RADT was performed in all patients, whereas throat culture could be performed in 1248 of them. Informed consent was obtained from the parents.

Results

The study group consisted of 1248 subjects who were admitted to the clinic with complaints of upper respiratory tract infection. There were 602 females (48.2%) and 646 males (51.8%), with a mean age of 6.3 ± 3.6 years (ranges: 4 months–17 years, median: 6.0 years). The patients were subdivided into three groups according to their ages—group 1: 0–6 years (n = 655); group 2: 7–12 years (n = 518) and group 3: 13 years and older (n = 75).

Taking the study group as a whole, the prevalence of GABHS was 35.9% (

Discussion

According to our results, prevalence of GABHS was highest in the 7–12-year age group which is concordant with the prevalence in school age group reported by American Academy of Pediatrics (AAP) (15–50%) [1].

Highly sensitive RADT for the diagnosis of streptococcal pharyngitis in school age children saves time both for parents and children to return to their work and school earlier, by helping the physician to make decision of antibiotic treatment without delay. Sensitivity of rapid detection

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