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Diagnostic accuracy of a rapid nucleic acid test for group A streptococcal pharyngitis using saliva samples: protocol
Robert Touitou1, Philippe Bidet2, Constance Dubois3
1Association Enseignement Formation Généralistes Hospitaliers - Croix Saint Simon, Paris, France.
Insights
This study evaluates a rapid nucleic acid test for group A streptococcus in saliva, aiming for a more convenient diagnosis of strep throat in children. The test shows promise for accurate detection without throat swabs.
Area of Science:
- Microbiology
- Infectious Diseases
- Diagnostic Accuracy Studies
Background:
- Group A Streptococcus (GAS) causes significant childhood pharyngitis, necessitating accurate diagnosis to guide antibiotic use.
- Conventional rapid antigen detection tests (RADTs) use throat swabs, while viral infections do not require antibiotics.
- Rapid nucleic acid amplification tests (NAATs) offer potential for improved GAS detection.
Purpose of the Study:
- To evaluate the diagnostic accuracy of a rapid NAAT performed on saliva for detecting GAS in children with pharyngitis.
- To compare the performance of salivary NAAT with conventional pharyngeal RADTs and a composite reference standard (throat culture and GAS PCR).
- To assess the feasibility and patient/physician satisfaction of using saliva-based NAAT in primary care settings.
Main Methods:
- A multicenter, prospective diagnostic accuracy study involving 800 children with pharyngitis.
- Comparison of a salivary rapid NAAT (Abbott ID NOW STREP A2) against a pharyngeal RADT (EXACTO PRO STREPTATEST).
- A composite reference standard including throat culture and GAS PCR was used for confirmation.
Main Results:
- The study aims to establish a minimally acceptable sensitivity of 80% for the salivary NAAT.
- Secondary outcomes include comparing sensitivity and specificity with the pharyngeal RADT, assessing variability with McIsaac scores, and evaluating time-to-result.
- Patient, physician, and parent satisfaction, along with barriers and facilitators to test use, will also be assessed.
Conclusions:
- The study hypothesizes that rapid NAATs performed on saliva are sufficiently sensitive for diagnosing GAS pharyngitis.
- Successful validation could lead to a less invasive and more convenient diagnostic method for strep throat in children.
- This could improve antibiotic stewardship by enabling accurate identification of GAS infections in primary care.
Background:
Group A streptococcus is found in 20-40% of cases of childhood pharyngitis; the remaining cases are viral. Streptococcal pharyngitis ("strep throat") is usually treated with antibiotics, while these are not indicated in viral cases. Most guidelines recommend relying on a diagnostic test confirming the presence of group A streptococcus before prescribing antibiotics. Conventional first-line tests are rapid antigen detection tests based on throat swabs. Recently, rapid nucleic acid tests were developed; they allow the detection of elements of the genome of group A streptococcus. We hypothesize that these rapid nucleic acid tests are sensitive enough to be performed on saliva samples instead of throat swabs, which could be more convenient in practice.
Methods:
This is a multicenter, prospective diagnostic accuracy study evaluating the performance of a rapid nucleic acid test for group A streptococcus (Abbott ID NOW STREP A2) in saliva, compared with a conventional pharyngeal rapid antigen detection test (EXACTO PRO STREPTATEST, lateral flow assay, comparator test), with a composite reference standard of throat culture and group A streptococcus PCR in children with pharyngitis in primary care (i.e., 27 primary care pediatricians or general practitioners). To ensure group A streptococcus is not missed, the salivary rapid nucleic acid test requires a minimally acceptable value of sensitivity (primary outcome) set at 80%. Assuming 35% of participants will have group A streptococcus, we will recruit 800 consecutive children with pharyngitis. Secondary outcomes will include difference in sensitivity between the pharyngeal rapid antigen detection test and the salivary rapid nucleic acid test; variability in sensitivity and specificity of the salivary rapid nucleic acid test with the level of McIsaac score; time to obtain the result of the salivary rapid nucleic acid test; patient, physician, and parents satisfaction; and barriers and facilitators to using rapid tests for group A streptococcus in primary care.
Ethics And Dissemination:
Approved by the Institutional Review Board "Comité de protection des personnes Ile de France I" (no. 2022-A00085-38). Results will be presented at international meetings and disseminated in peer-reviewed journals.
Trial Registration Number:
ClinicalTrials.gov: NCT05521568.
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