Related Experiment Videos
[Cutaneous response to 2 and 10 units of tuberculin in infants]
1Departamento Pediatría, Escuela de Medicina, Pontificia Universidad Católica de Chile.
Insights
This study on infant tuberculin skin testing found that while both 2 TU and 10 TU purified protein derivative (PPD) showed similar results, higher PPD doses increased reactions over 15 mm. A booster effect was observed in some infants after retesting.
Area of Science:
- Immunology
- Pediatrics
- Infectious Disease
Background:
- Bacille Calmette-Guérin (BCG) immunization is widely used globally.
- Assessing cell-mediated immunity in infants post-BCG vaccination is crucial for tuberculosis surveillance.
- Tuberculin skin testing (TST) is a common method to evaluate immune response.
Purpose of the Study:
- To evaluate the cutaneous response to different doses of purified protein derivative (PPD) in BCG-vaccinated infants.
- To compare the efficacy of 2 TU and 10 TU PPD in detecting tuberculin hypersensitivity.
- To investigate the booster effect in infants with negative TST results.
Main Methods:
- A double-blind, open study involving 304 healthy infants aged 3-18 months with BCG scars.
- Infants received either 2 TU or 10 TU of PPD.
- Cutaneous reactions were measured, and a subset of infants with low reactions underwent retesting.
Main Results:
- No significant difference in mean reaction size or positive responses (≥10 mm) between 2 TU and 10 TU PPD.
- Cutaneous reactions ≥15 mm were more frequent with 10 TU PPD.
- A booster effect was observed in 25% of BCG-scarred infants and 12.5% of non-scarred infants upon retesting.
Conclusions:
- Both 2 TU and 10 TU PPD are comparable for detecting tuberculin hypersensitivity in BCG-vaccinated infants.
- Higher PPD doses (10 TU) may increase the frequency of larger reactions (≥15 mm).
- The booster phenomenon is present in BCG-vaccinated infants, suggesting a potential need for repeat testing in low responders.
Abstract:
A study was done in 322 healthy, well nourished infants, 3 to 18 months old from day care centers of metropolitan Santiago, Chile, that were given BCG immunization in their neonatal period: 304 (94.4%) of them showed BCG scars and were included in a double blind open study, to determine the cutaneous responses to 2 TU and 10 TU tuberculin (PPD). There were no differences in the mean size of cutaneous reactions nor in percent positive responses (greater than or equal to 10 mm), but cutaneous reactions greater than or equal to 15 mm were more frequent in infants tested with PPD 10 TU. In 184 out of 304 infants (60.5%) tuberculin reactions were negative (less than or equal to 10 mm). Eighteen out of 322 infants (5.6%) that didn't show BCG scars were injected with PPD 2 TU: tuberculin reactions sized 6 to 9 mm were recorded in 3/18 of these infants but none of them attained 10 mm. Fifty five infants whose tuberculin reactions were 5 mm or less were retested: a booster effect was likely from the appearance of enhanced dermal response after a second tuberculin test done with the same or higher tuberculin strength than the first one in 12/47 of these infants with BCG scar (25%) and in only 1/8 such subjects without BCG scar.