Comparison of group A streptococcal titres in healthy children and those with pharyngitis and skin infections

Risk factors for group A streptococcal pharyngitis and skin infections: A case control study

Background

Group A streptococcal (GAS) infections can trigger an immune-mediated response resulting in acute rheumatic fever (ARF). The role of social and environmental risk factors for GAS pharyngitis and skin infections are not well understood. This study aimed to identify factors associated with GAS pharyngitis and skin infections, and to determine if these are the same as those for ARF.

Methods

A case-control study, including 733 children aged 5-14 years, was undertaken between March 2018 and October 2019 in Auckland, New Zealand. Healthy controls (n = 190) and symptomatic cases including GAS pharyngitis (n = 210), GAS seronegative carriers (n = 182), and GAS skin infections (n = 151) were recruited. Trained interviewers administered a comprehensive, pre-tested, face-to-face questionnaire.

Findings

Multivariable analysis identified strong associations between barriers to accessing primary healthcare and having GAS pharyngitis (adjusted OR 3·3; 95% CI 1·8-6·0), GAS carriage (aOR 2·9; 95% CI 1·5-6·0) or a GAS skin infection (aOR 3·5; 95% CI 1·6-7·6). Children who had GAS skin infections were more likely than all other groups to report living in a crowded home (aOR 1·9; 95% CI 1·0-3·4), have Māori or Pacific grandparents (aOR 3·0; 95% CI 1·2-7·6), a family history of ARF (aOR 2·2; 95% CI 1·1-4·3), or having a previous diagnosis of eczema (aOR 3·9; 95% CI 2·2-6·9).

Interpretation

Reducing barriers to accessing primary healthcare (including financial restrictions, the inability to book an appointment, lack of transport, and lack of childcare for other children) to treat GAS pharyngitis and skin infections could potentially reduce these infections and lead to a reduction in their sequelae, including ARF. These strategies should be co-designed and culturally appropriate for the communities being served and carefully evaluated.

Funding

This work was supported by the Health Research Council of New Zealand (HRC), award number 16/005.

Study of streptococcal antibody (anti-streptolysin O) among healthy children in Bangladesh

Objectives:

The standard reference value of anti-streptolysin O (ASO) titre for diagnosing acute rheumatic fever (RF) in children is yet to be determined in Bangladesh. We aimed to measure the upper limit of the normal (ULN) of ASO titre among healthy children to determine the cut-off value for the diagnosis of RF in Bangladesh.

Methods:

A total of 400 healthy children aged 5–15 years with no history of fever, sore throat and impetigo during the last 8 weeks of the study were enrolled. The respondents were randomly selected from an urban non-slum area, an urban slum area and a rural area of Bangladesh. ASO titre was measured using a turbidimetric immunoassay based on the principle of an agglutination reaction. The 80th percentile value was considered as the ULN of ASO titre.

Results:

Approximately 55% of the children were male. The mean (SD) age of children was 9.1 (2.7) years. The ULN of ASO titre for 5–15 years aged children was 217.4 IU/mL.

Conclusion:

Our reference value of ASO titre at the 80th percentile will be an essential guide for clinicians to diagnose acute RF.

OUP accepted manuscript

Background

Group A Streptococcus (GAS) causes superficial pharyngitis and skin infections as well as serious autoimmune sequelae such as acute rheumatic fever (ARF) and subsequent rheumatic heart disease. ARF pathogenesis remains poorly understood. Immune priming by repeated GAS infections is thought to trigger ARF, and there is growing evidence for the role of skin infections in this process.

Methods

We utilized our recently developed 8-plex immunoassay, comprising antigens used in clinical serology for diagnosis of ARF (SLO, DNase B, SpnA), and 5 conserved putative GAS vaccine antigens (Spy0843, SCPA, SpyCEP, SpyAD, Group A carbohydrate), to characterize antibody responses in sera from New Zealand children with a range of clinically diagnosed GAS disease: ARF (n = 79), GAS-positive pharyngitis (n = 94), GAS-positive skin infection (n = 51), and matched healthy controls (n = 90).

Results

The magnitude and breadth of antibodies in ARF was very high, giving rise to a distinct serological profile. An average of 6.5 antigen-specific reactivities per individual was observed in ARF, compared to 4.2 in skin infections and 3.3 in pharyngitis.

Conclusions

ARF patients have a unique serological profile, which may be the result of repeated precursor pharyngitis and skin infections that progressively boost antibody breadth and magnitude.