Potential for Molecular Testing for Group A Streptococcus to Improve Diagnosis and Management in a High-Risk Population: A Prospective Study

Abstract

Background In high-burden settings, guidelines recommend antibiotic treatment for all suspected group A Streptococcus (GAS) infections to prevent rheumatic fever and poststreptococcal glomerulonephritis. Highly sensitive rapid GAS tests could reduce unnecessary antibiotic use in these settings. Methods This was a prospective study of the Xpert Xpress Strep A (Cepheid) molecular test compared with culture of throat swab samples collected at a referral hospital in northern Australia. Demographic and clinical data and results of streptococcal serology and culture were collected. Results Of 164 throat swab samples, 145 (88%) were eligible for inclusion; 49 (34%) were molecular test positive and 24 (17%) were culture positive for GAS. The sensitivity, specificity, and positive and negative predictive values for the molecular test versus culture were 100.0%, 79.3%, 48.8%, and 100.0%, respectively. Among 25 samples testing positive with the molecular test and negative with culture, group C or G streptococci were cultured in 2, and a plausible clinical explanation, such as pharyngotonsillitis, or rheumatic fever with positive results of streptococcal serology, was apparent in 19 instances. In 25 patients with rheumatic fever or poststreptococcal glomerulonephritis diagnoses, molecular testing nearly trebled the detection of GAS in throat swab samples, from 3 (12%) detected with culture to 8 (32%) detected with molecular testing. Reasons for “false-positive” molecular test results could include the presence of GAS below the threshold of culture detection or persistence of nonviable organisms after infection. Conclusion Implementation of molecular testing could improve antibiotic use in this high-burden setting. The incremental yield in poststreptococcal syndromes, by which time cultures are negative, has high potential in the diagnostic workup of autoimmune poststreptococcal syndromes and warrants further investigation.

Ending rheumatic heart disease in Australia: the evidence for a new approach

“…For example, diagnosis of Strep A skin infections can usually be made by trained clinicians on the basis of typical wound appearance and confirmed with microbial swabs if needed 161. However, distinguishing Strep A throat infections from viral infection on clinical appearance is more difficult 15,176. New generation point‐of‐care tests using polymerase chain reaction to identify Strep A in remote Aboriginal and Torres Strait Islander settings may be a useful diagnostic adjunct, and this warrants further research 176…”

An urgent need for antimicrobial stewardship in Indigenous rural and remote primary health care

“…Antimicrobials are also used more often for sore throat treatment to prevent serious complications such as rheumatic heart disease . Other contributors to high rates of antimicrobial use include the absence of senior clinical staff and high staff turnover rates, lack of diagnostic capability, and remoteness (where lack of treatment may precipitate the need for retrieval to a distant hospital). Point‐of‐care tests may be useful in helping to select which patients will most benefit from antibiotics (and which will not).…”

Prevalence of Group A Streptococcus in Primary Care Patients and the Utility of C-Reactive Protein and Clinical Scores for Its Identification in Thailand

“…Diagnosing GAS and deciding whether antibiotics are needed remain challenging, and the best approaches will vary depending on the setting, availability of health care and diagnostics, as well as the prevalence of GAS infections, carriage, and complications such as rheumatic heart disease. 7,21,42 In Thailand, where a comprehensive primary healthcare system exists, most of the population have access to universal health coverage, and antibiotics are available from pharmacies and stores. 43,44 Diagnostic tests for GAS are not routinely available in primary care.…”

“…2,[17][18][19][20] Rapid molecular tests for GAS are also being developed and have proved valuable in settings such as northern Australia, where a high burden of GAS, acute post-streptococcal glomerulonephritis, and acute rheumatic fever is evident. 21 Our main objective was to evaluate the performance of CRP in identifying the presence of GAS among people consulting with sore throat and fever in Chiang Rai's government-run primary care units. The secondary objectives were to estimate the prevalence of GAS and other key pathogens, study the antibiotic susceptibility of GAS isolates, and compare the performance of CRP against the Centor and FeverPAIN clinical scores.…”