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The booster effect with repeat tuberculin testing in children and its relationship to BCG vaccination
1Department of Paediatrics, 1 Military Hospital, Voortrekkerhoogte, Tvl.
Insights
Tuberculin skin testing in children can show a "booster effect," not true tuberculosis infection, especially after BCG vaccination. This phenomenon, observed in preschoolers, highlights the need for careful interpretation of test results.
Area of Science:
- Pediatrics
- Infectious Diseases
- Immunology
Background:
- Tuberculin skin testing (TST) is crucial for tuberculosis (TB) diagnosis.
- Booster effects can influence TST results, potentially mimicking true infection.
- BCG vaccination status may impact TST responses.
Purpose of the Study:
- To investigate the occurrence and characteristics of the booster phenomenon in children attending a daycare center.
- To differentiate between true tuberculous infection and the booster effect on TST results.
Main Methods:
- Two Mantoux tuberculin tests were administered 8 weeks apart to 127 children (6 months–14 years).
- TST results were analyzed based on age, BCG vaccination status, and reaction size.
- Prevalence of positive reactions and conversions were assessed.
Main Results:
- Initial TST showed 19.7% of children with reactions ≥10 mm, more common in older, twice-vaccinated children.
- Repeat TST revealed a significant increase in mean reaction size.
- 13% of children converted to tuberculin positivity, particularly preschoolers with BCG scars.
Conclusions:
- The observed increase in TST reactions and conversions was attributed to the booster effect, not active TB infection.
- The booster effect is notable in children, especially those with BCG scars, and can be mistaken for true TB infection.
- Understanding the booster phenomenon is vital for accurate interpretation of TST in pediatric populations.
Abstract:
One hundred and twenty-seven children, aged 6 months - 14 years, attending a day-care centre in Pretoria had two Mantoux tuberculin tests performed 8 weeks apart. On initial testing 19.7% of the children had reactions greater than or equal to 10 mm and positive tests were commoner in the older children--who had received BCG vaccination twice. On repeat testing a significant increase in the mean tuberculin reaction size was noted and 13% of the children converted to tuberculin positivity. Since an extensive search revealed no evidence of active tuberculosis in either children or adults at the day-care centre, it was concluded that the observed enhancement of the tuberculin reactions was due to the booster effect. This phenomenon was most marked in preschoolers with a BCG scar. It is important to recognise that boosting can occur in children and may be confused with true conversion to tuberculin positivity caused by infection with Mycobacterium tuberculosis.