Oral Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Evaluation of clinical decision rules for diagnosis of Streptococcus pyogenes pharyngitis in a tropical setting (119034)

John Hart 1 2 , Jimaima Kailawadoko 3 , Tria Williams 1 4 , Jyotishna Mani 3 , Ilikena Malo 3 , Tuliana Cua 1 , Natalie Caltabiano 1 , Jasmyn Voss 1 , Kristy Azzopardi 1 , Matthew Parnaby 1 , Sanjeshni Autar 5 , Komal Chand 5 , Lavenia Lagilagi 3 , Jessica Paka 3 , Eric Rafai 5 , Joseph Kado 6 , Hannah Frost 1 2 , Andrew Steer 1 2 4
  1. Murdoch Children's Research Institute, Parkville, VIC, Australia
  2. The University of Melbourne, Melbourne, Australia
  3. Cure Kids Fiji, Rheumatic Heart Disease Support Programme, Suva, Fiji
  4. The Royal Children's Hospital, Melbourne, Australia
  5. Ministry of Health and Medical Services, Suva, Fiji
  6. The Kids Research Institute Australia, University of Western Australia, Perth, Australia

Background
Acute rheumatic fever is an immune-mediated condition triggered by Streptococcus pyogenes sore throat and possibly skin infection, with a substantial burden in resource-limited settings. Clinical decision rules (CDRs) are commonly used to guide antibiotic treatment of sore throat based on signs and symptoms, but their diagnostic accuracy varies by study and setting. This work aimed to assess the accuracy of multiple CDRs in Fiji to diagnose S. pyogenes sore throat.

Methods
We conducted a prospective diagnostic accuracy study at two primary healthcare centres in Suva, Fiji, enrolling 5–15-year-old children presenting with sore throat. Clinical features were assessed, and two throat swabs were collected from each participant for S. pyogenes detection using culture and a point-of-care nucleic acid amplification test (NAAT). Six CDRs were evaluated against NAAT and culture as reference standards.

Results
Of 250 participants, S. pyogenes was detected among 31.7% by NAAT and 10.4% by culture. The Fiji CDR demonstrated high sensitivity (98.7% vs. NAAT; 100% vs. culture) but very low specificity (5.3% vs. NAAT; 4.5% vs. culture). All CDRs had poor discriminatory power (area under receiver operating characteristic curve: 0.48–0.53).

Conclusion
CDRs cannot accurately diagnose S. pyogenes sore throat in this tropical setting where rheumatic fever is common. There is a high burden of S. pyogenes sore throat in Fiji, apparently underestimated when traditional culture-based methods are used. Although NAAT testing offers higher sensitivity than culture, the costs remain high. There is an urgent need for accurate, affordable diagnostics to guide sore throat management in resource-limited settings.