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Comparative study of skin testing with PPD and new tuberculins by the WHO Mantoux test
M Tala-Heikkilä1, E Lemma, J L Stanford
1Department of Paediatrics, University Central Hospital of Turku, Finland.
Insights
New tuberculin (NT) preparations showed more specific skin indurations compared to PPD RT 23 tuberculin in BCG-vaccinated children, suggesting improved diagnostic potential for tuberculosis screening.
Area of Science:
- Immunology
- Infectious Diseases
- Public Health
Background:
- Tuberculosis (TB) diagnosis relies on accurate tuberculin skin testing.
- Bacille Calmette-Guérin (BCG) vaccination can affect tuberculin test results.
- Evaluating new tuberculin preparations is crucial for improving TB diagnostics.
Purpose of the Study:
- To compare the diagnostic performance of PPD RT 23 tuberculin with two new tuberculin (NT) batches.
- To assess the concordance and specificity of skin indurations in BCG-vaccinated children.
Main Methods:
- A double-test Mantoux study was conducted in Finnish schoolchildren (11-13 years old) vaccinated with BCG at birth.
- Children received either PPD RT 23 and NT batch T1327 (614 children) or PPD RT 23 and NT batch T1456 (312 children).
- Results were compared with previous data from Ethiopian children using PPD RT 23 and T1327.
Main Results:
- PPD RT 23 and the NT batches showed significant linear correlations in skin induration readings.
- New tuberculin preparations yielded fewer zero reactions, indicating higher specificity than PPD RT 23.
- Mean induration sizes were slightly smaller for PPD RT 23 compared to NT batches.
Conclusions:
- PPD RT 23 and the new tuberculin preparations yield concordant results in Mantoux tests.
- New tuberculin preparations appear more specific, potentially due to retained species-specific antigens.
- Variations in reaction sizes may reflect responses to different antigens or immunological mechanisms.
Abstract:
PPD RT 23 tuberculin and two batches of new tuberculin (NT) were tested for concordant skin indurations in the WHO standard Mantoux test in 11- to 13-year-old Finnish school children BCG vaccinated at birth. All were double tested with RT 23 and with either batch T1327 (614 children) or with batch T1456 (312 children) of NT. The results were compared with data available from an earlier study employing RT 23 and T1327 in Ethiopian children, 50/134 of whom had a BCG scar. The mean induration to RT 23 after 72 h was slightly smaller than to the NTs. The individual readings for RT 23 had significant linear correlations with T1327 in Finland (r = 0.77) and in Ethiopia (r = 0.89), and for T1456 (r = 0.83; P < 0.001 for all three). Zero reactions were much fewer to NTs (5.5% to T1327 and 0.3% to T1456) than to RT 23 in Finland (18.2% and 9.3% respectively for the two groups). The results were similar in Ethiopian children. Our results indicate that RT 23 and the two NTs give concordant results, but NTs seem to be more specific, perhaps because they retain more species-specific antigens. Analysis of our results suggests that different peaks in the distribution of reaction sizes were due to responses to different antigens or combinations of antigens, and in the case of the largest reactions, to a different type of immunological response.