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Molecular and clinical diagnosis of group A streptococcal pharyngitis in children

Susanna Felsenstein1, Diala Faddoul2, Richard Sposto3

  • 1Division of Infectious Diseases, Department of Pediatrics, Children's Hospital Los Angeles and Keck School of Medicine of University of Southern California, Los Angeles, California, USA sfelsenstein@chla.usc.edu.

Journal of Clinical Microbiology
|August 22, 2014
PubMed

Insights

A new illumigene assay significantly improves the detection of Group A Streptococcus (GAS) pharyngitis in children compared to rapid antigen detection tests and culture. This sensitive diagnostic tool aids in timely treatment to prevent complications.

Area of Science:

  • Pediatric Infectious Diseases
  • Clinical Microbiology
  • Molecular Diagnostics

Background:

  • Group A Streptococcus (GAS) pharyngitis is a common childhood illness requiring accurate diagnosis for effective treatment and prevention of sequelae.
  • Current diagnostic methods like rapid antigen detection tests (RADTs) and throat cultures have limitations in sensitivity and speed.
  • There is a need for improved diagnostic tools to accurately identify GAS pharyngitis in pediatric patients.

Purpose of the Study:

  • To evaluate the performance of a loop-mediated isothermal amplification (LAMP) assay, the illumigene assay, for diagnosing GAS pharyngitis in children.
  • To compare the sensitivity and specificity of the illumigene assay against RADT and standard culture methods.
  • To assess the clinical utility of the illumigene assay in identifying GAS pharyngitis, particularly in children meeting specific clinical criteria.

Main Methods:

  • A loop-mediated isothermal amplification (LAMP) assay (illumigene) was compared with RADT and throat culture on 361 pediatric throat swab samples.
  • Discrepant results were resolved using an alternative molecular assay.
  • Clinical presentations and scores (McIsaac) were correlated with test results in GAS-positive patients.

Main Results:

  • The illumigene assay detected 70 out of 71 GAS-positive samples, demonstrating significantly higher sensitivity than RADT (35/71) and culture (55/71).
  • The assay increased the identification of GAS-positive cases among eligible children, with a specificity comparable to culture.
  • The illumigene assay showed higher detection rates in children with higher McIsaac scores (≥4) compared to RADT and culture.

Conclusions:

  • The illumigene assay is a highly sensitive and specific molecular diagnostic tool for Group A Streptococcus pharyngitis in children.
  • Its rapid results and superior performance make it a valuable alternative to traditional methods for laboratory diagnosis.
  • This assay can improve the timely and accurate diagnosis of GAS pharyngitis, facilitating appropriate antimicrobial therapy and preventing post-infectious complications.

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