KEY POINTS
- Group A Streptococcus (GAS) may be carried without symptoms. When it causes illness, the presentation ranges from pharyngitis and other local infections to toxin-mediated disease and post-infectious immune complications.
- Clinical findings and scoring systems help estimate the likelihood of GAS pharyngitis, but none can confirm or exclude it in a child who has no clear viral features.
- Culture, rapid antigen testing and nucleic acid amplification testing offer benefits with different trade-offs. A test is worth doing only if its result can change the child’s management and supports antimicrobial stewardship.
- Before considering microbiological testing, assess the child for serious illness. Suspected sepsis, invasive GAS (iGAS) and scarlet fever requires prompt treatment and escalation.
CLINICAL SPECTRUM OF GROUP A STREPTOCOCCUS
Group A Streptococcus (GAS) is the clinical name commonly used for Streptococcus pyogenes. It is a Gram-positive coccus, usually seen in chains, that produces complete beta-haemolysis on blood agar and carries the Lancefield group A cell-wall carbohydrate. The older term group A beta-haemolytic streptococcus (GABHS) refers to the same organism and highlights key differentiating features (Spellerberg and Brandt, 2022).
Children can carry GAS in the throat, on the skin or in the anogenital tract without being ill. Transmission is associated with close contact and respiratory particles, and pharyngitis usually appears two to five days after exposure. School and nursery outbreaks are more likely where children mix in close contact with one another. Carriage is clinically important because a positive throat result does not always explain the current illness (UKHSA, 2025; Centers for Disease Control and Prevention, 2025; Oliver et al., 2018). Pharyngitis is seen most often between 5 and 15 years of age and is uncommon in children under 3 years.
GAS is also encountered in other infections such as impetigo, cellulitis, cervical lymphadenitis and pneumonia. Toxin-producing strains are responsible for scarlet fever, presenting with sandpaper rash, Pastia’s lines and strawberry tongue, and may also cause streptococcal toxic shock. Acute rheumatic fever and glomerulonephritis occur through a different, post-infectious immune mechanism (Ohashi et al., 2024).
The uncommon presentation that must not be missed is invasive GAS (iGAS), defined by infection at a normally sterile site, such as blood. It may present as sepsis, necrotising fasciitis, myositis, osteomyelitis, meningitis, pneumonia or empyema, and deterioration can be rapid. Respiratory distress, poor perfusion, altered behaviour, tachycardia, rapidly spreading soft-tissue inflammation, pain out of proportion to the examination, or deterioration after an apparently viral illness should prompt urgent assessment regardless of the throat findings. In clinical practice, Paediatric Early Warning (PEW) scores and sepsis stratification tools should be included in the assessment, and particular weight given to carer concerns and clinical intuition. Scarlet fever and iGAS are notifiable in England (UKHSA, 2025).
Recent surveillance is a reminder that this is not only a historical disease. During the 2022-2023 resurgence, England recorded 55,872 scarlet-fever notifications. There were also 426 deaths from any cause within seven days of an iGAS diagnosis, including 48 among people aged under 18 (UKHSA, 2023).
CLINICAL ASSESSMENT AND SCORING
Take a previously well 5-year-old who has been unwell for two days. His temperature is 39.2°C, swallowing is painful and he is drinking less. There is no cough or coryza. On examination his tonsils are markedly inflamed with purulent exudate, although the anterior cervical nodes are not tender. He has no rash or clinical features of sepsis, toxic shock or invasive disease. His FeverPAIN score is 5, which increases the probability of GAS but does not establish the diagnosis.
This is a familiar presentation, but the appearance of the throat and other clinical signs are not diagnostic. GAS accounts for about 20-30% of childhood pharyngitis, with variation by age, season and setting (Centers for Disease Control and Prevention, 2025; Oliver et al., 2018). Sudden sore throat, fever, palatal petechiae, tender anterior cervical nodes and tonsillar exudate make GAS more likely. Cough, rhinorrhoea, hoarseness, conjunctivitis and oral ulcers point more towards a viral infection. In the absence of those viral features, examination alone remains non-diagnostic.
Clinical scores are useful for handling that uncertainty. FeverPAIN includes recent fever, purulence, presentation within three days, severe tonsillar inflammation, and the absence of cough or coryza. Centor uses exudate, tender anterior cervical nodes, temperature above 38°C, and no cough; McIsaac adds an age adjustment. However, these scores estimate probability rather than identify the organism (Pellegrino et al., 2023; Linder et al., 2025).
NICE guidelines recommend using FeverPAIN or Centor scores to guide either no, delayed or immediate antibiotic prescribing. NICE’s 2019 technology guidance did not recommend routine adoption of rapid testing because the validity of results, additional clinical benefit and cost-effectiveness were uncertain (NICE, 2018; NICE, 2019). However, it is likely that over the last 7-8 years the health economic and technological landscape has evolved and a more contemporary evidence base is warranted. The more recent 2025 IDSA update takes a different approach: clinical scores are used mainly to select patients for microbiological testing. Though it remains recognised that scores are less helpful in children under 3 years, who may have atypical presentations (Linder et al., 2025).
In a stable child aged 3 years or older without viral features, a validated score can identify those for whom microbiological testing may change treatment or advice (Linder et al., 2025).
Recommendations around the world also reflect the local risk of rheumatic fever. The Canadian Paediatric Society advises point-of-care testing and/or culture before antibiotics in selected children at low risk of rheumatic fever. In high-burden communities, it recommends testing children aged 3 years or older with a sore throat and confirming a negative point-of-care result by culture (Canadian Paediatric Society, 2021). A review of 19 national and international guidelines identified three broad approaches, largely explained by differences in rheumatic-fever risk and health-system context (Pellegrino et al., 2023). WHO places the detection and treatment of suspected GAS pharyngitis alongside the primary prevention of rheumatic fever and rheumatic heart disease in populations where risk is highest (World Health Organization, 2024).
LIMITATIONS OF A “NO-TESTING” APPROACH
The drawback of not testing is not simply diagnostic uncertainty: the antibiotic decision then rests on a score that cannot reliably identify GAS. In Welsh pharmacy data from patients aged 6 years or older, FeverPAIN alone would have missed 44% of point of care positive cases and led to unnecessary antibiotics in 23% of test-negative cases (Bustamante et al., 2026). In a primary-care study of 160 patients, only 22.7% of those with Centor scores above 2 were positive by molecular testing. Once testing was introduced, immediate and delayed prescriptions fell by 55-65% (Daniels, Miles and Button, 2024). Other work has found similar disagreement between clinical scores and test results (Daniels, El Omda and Mokbel, 2024).
These findings do not however justify testing every sore throat. They do suggest that, in a selected child, a same-day visit result can make the prescribing decision more accurate. Antibiotics were supplied to 72.7% of patients in an English score-based pharmacy pathway, compared with 29.9% in a Welsh pathway supported by point of care testing; differences in eligibility, training and pathway design limit a direct comparison (Matuluko et al., 2025). Paediatric emergency-department abstracts have reported 96.8% sensitivity, 88.1% specificity and 98.7% negative predictive value for one molecular assay, and a 25-minute reduction in median stay after point of care testing was introduced (Durand et al., 2024; Tran et al., 2023). At present, the clearest benefit is a faster, more selective antibiotic decision, which is shown to be more preferable by families also (Daniels, Miles and Button, 2024). Effects on transmission, admission and invasive disease remain uncertain.
SELECTING A DIAGNOSTIC TEST
Culture remains the reference standard method because it detects viable bacteria and leaves an isolate available for further work up including susceptibility to antimicrobials. With a well-taken and properly processed sample, sensitivity is at least 90%. The practical disadvantage is the wait of up to 48 hours, which delays the bedside decision and requires reliable follow-up of results. Culture also does not solve the problem of carriage: a positive result may not be the cause of the child’s symptoms (Spellerberg and Brandt, 2022).
Rapid antigen tests are useful when a result is needed during the consultation. They usually detect group A antigen in usually under fifteen minutes and are highly specific, but reported sensitivity ranges from approximately 58% to 96%. Whether a negative result in a child needs confirmation by culture depends on the assay and the local guidance being followed (Spellerberg and Brandt, 2022).
Nucleic acid amplification tests offer a different balance. Results may be available within minutes, and sensitivity appears higher than that for antigen tests (Cohen, Tanz and Shulman, 2024). The trade-offs can be cost, equipment and training. High sensitivity however can also detect carriage or a low bacterial load that is not responsible for the illness, although this may be more useful in difficult to swab resisting children. One molecular assay had a lower analytical detection limit than three lateral-flow assays (Chandrasekaran et al., 2025). Better analytical performance improves care when the result is used in an appropriate clinical pathway (Hain et al., 2026).
Serology has a separate role. Antistreptolysin O and anti-DNase B measure a delayed immune response and may help investigate selected post-streptococcal complications; they are not tests for acute pharyngitis (Spellerberg and Brandt, 2022). Whichever acute test is chosen, the clinician should be clear about the question being asked, whether the result will be available in time to make a difference to patient care, and how age, presentation, prevalence and carriage affect its interpretation.
EXPERIENCE FROM OUR LOCAL PATHWAY
Our Paediatric Assessment Unit (PAU) pathway in South East England starts with severity rather than a throat score. A child who is febrile, appears systemically unwell, has a raised PEW score, or causes particular concern to a carer enters the sepsis pathway for early senior review and treatment. At that stage, clinicians consider iGAS, pneumonia and empyema. Suspected scarlet fever is treated promptly without waiting for point of care result, and vulnerable children at high risk of complications are managed regardless of their clinical score.
Only after this safety screen do stable children with uncomplicated tonsillitis or pharyngitis enter the testing branch. A FeverPAIN score of 0 to 1 usually leads to self-care; scores of 2 to 5 are eligible for the locally available Strep A point of care test, with treatment linked to the result. When testing is unavailable, clinicians return to the score-based NICE approach. Analgesia, hydration, reassurance and clear safety-netting are part of the consultation whatever the result. For non-severe disease, the pathway uses penicillin-based treatment and follows local antimicrobial advice for true penicillin allergies. NICE recommends 5 to 10 days of phenoxymethylpenicillin for acute sore throat but comments that 10 days may be more likely to improve microbiological cure (NICE, 2018). A child with scarlet fever should stay away from school or nursery until 24 hours after antibiotics are started (UKHSA, 2019).
An anonymised PAU service log recorded 140 point of care test attempts between 13 January and 12 July 2026: 25 positive, 101 negative and 14 invalid. Among the 126 valid results, 19.8% were positive. The invalid rate was 10.0%, possibly because of sampling or test technique. Seven invalid entries were followed by a same-day valid entry for the same date of birth, which is consistent with repeat testing. Children younger than 3 years accounted for 71 of the 140 attempts; 5 of 66 valid results in this age group were positive (7.6%), demonstrating our centers experience of lower positivity in children under 3 years and the need to follow clinical pathways.
Experience from another NHS center shows why testing criteria matter. During its rapid roll-out, 41% of 1,388 children tested had no documented pharyngitis or similar indication, while one in five test-negative children with a relevant presentation still received antibiotics (Shorrocks et al., 2024). Introducing a test therefore needs more than buying the equipment: eligibility, swab technique, quality control, infection prevention, result capture and prescribing practice all need to be reviewed.
CONCLUSION
Group A streptococcal infection is a common cause of childhood infections, with manifestations ranging from uncomplicated pharyngitis to potentially life-threatening invasive disease. The first priority is always to recognise serious illness and initiate timely treatment when scarlet fever, sepsis or invasive GAS infection is suspected. For the much larger group of children presenting to healthcare providers with uncomplicated sore throat, distinguishing bacterial from viral infection can be a diagnostic challenge clinically because signs, symptoms and scoring systems estimate likelihood of GAS cause, but do not confirm the diagnosis.
The practical question remains, which children are likely to benefit from microbiological testing and which modality should be used? In a stable child aged 3 years or older without viral features, a validated score can identify those for whom microbiological testing may change treatment or advice (Linder et al., 2025). In these selected children, microbiological testing can help reduce diagnostic uncertainty and support more informed prescribing decisions, without displacing self-care or safety-netting advice. It may also support the UK’s target to reduce human antibiotic use by 5% from the 2019 baseline by 2029 (HM Government, 2024).
Bacterial culture, rapid antigen testing and molecular assays each have advantages and limitations, and the choice of test should reflect the clinical setting, turnaround time and accuracy of the result. Most importantly however, a thorough structured clinical assessment remains the priority to exclude serious illness and where appropriate, microbiological testing should be incorporated into evidence-based clinical pathways rather than used in isolation.
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DECLARATIONS
The educational presentation on which this article draft is based was sponsored by Abbott. The clinical opinions in that presentation were those of the author and not necessarily those of Abbott or the author’s employing organisations. Generative AI was employed to structure and proof-read the article.
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