SAGE IVD recommended including the Group A Streptococcus antigen test category in the EDL 3:
• as a disease-specific IVD for use in community settings and health facilities without laboratories and as a disease-specific IVD for use in clinical laboratories (EDL 3, Sections I.b and II.b);
• using an RDT or immunoassay format;
• to aid in the diagnosis of Group A Streptococcal pharyngitis. The group clarified the need for the dual listing in Sections I.b and II.b of the EDL, saying that while the rapid antigen detection test (RADT) can be used in primary care settings, most guidelines require culture confirmation of a negative test (because rapid tests have lower specificities than immunoassays). SAGE IVD also highlighted the potential for this test to be grossly overused, and it emphasized the value of adding a note on rational use to this entry in the EDL. To this end, while acknowledging that the EDL is designed to be a policy support document rather than a guide to medical use, SAGE IVD recommended considering the inclusion of an additional column in future editions of the EDL, where comments or qualifications of importance can be made.

Group A Streptococcus (GAS) pharyngitis is a common and severe condition, especially among children, for which there is no test currently listed in the EDL. Because prompt and adequate treatment improves the prognosis of GAS pharyngitis, rapid diagnosis is a requisite of children’s primary care worldwide. The proposed IVD have enough potential for adequate diagnosis and are both convenient and cost-effective. The current gold standard (throat culture) takes too long to deliver results and is often unavailable in facilities in LMICs. Importantly, a POC test for GAS pharyngitis could help avoid unnecessary use of antibiotics, thereby contributing to lower health care costs, fewer adverse events and reduced risk of antibiotic resistance. SAGE IVD noted the very recent publication of a systematic review on the impact of GAS rapid antigen detection test (RADT) which shows that they reduce antibiotic use by 8% and antibiotic prescription by 25% (14).

The evidence of the diagnostic accuracy of Group A Streptococcus (GAS) rapid antigen detection test (RADT) to aid in the diagnosis of GAS pharyngitis has been summarized in three comprehensive systematic reviews, all with similar findings. The evidence base is substantial, and average sensitivity and specificity of the RADTs is 85% and 95%, respectively; this has not been found to vary systematically with test technology – LFIAs, EIAs and OIAs (optical immunoassays) – or age group (adults and children). Although the reviews have revealed methodological weaknesses in the primary studies, these do not appear to influence the observed accuracy. Unexplained heterogeneity in accuracy has been noted, and there may be variations between test brands or versions; but no clear explanations have been given. Use in patients where the prevalence of GAS is 30% yields positive predictive values of 88% and negative predictive values of 94%. Guidelines suggest that the positive predictive value is high enough to recommend antibiotics. But guidelines also judge that the risk of missing infection in children is high and recommend that those testing negative also have culture to confirm diagnosis within 24–48 h. The negative RADT result is seen as adequate to withhold antibiotics in adults. Evidence of the impact of RADTs is mixed, and likely to depend on current local practice, although it has been shown to reduce antibiotic use.

World Health Organization. (‎2021)‎. The selection and use of essential in vitro diagnostics: report of the third meeting of the WHO Strategic Advisory Group of Experts on In Vitro Diagnostics, 2020 (‎including the third WHO model list of essential in vitro diagnostics)‎. World Health Organization. https://iris.who.int/handle/10665/339064