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Tuberculin test conversion during repeated skin testing, associated with sensitivity to nontuberculous mycobacteria
The American Review of Respiratory Disease
|July 1, 1979
Summary
Repeating the tuberculin test (purified protein derivative) within one month can cause false-positive results. This tuberculin conversion is linked to prior sensitivity to nontuberculous mycobacteria, highlighting population variability in test interpretation.
Area of Science:
- Infectious Diseases
- Immunology
- Public Health
Background:
- The tuberculin skin test (TST) is crucial for diagnosing tuberculosis (TB) infection.
- Understanding factors influencing TST conversion is vital for accurate TB screening.
- Previous exposure to nontuberculous mycobacteria can affect TST results.
Purpose of the Study:
- To investigate if repeating the tuberculin test (purified protein derivative) shortly after the initial test can lead to tuberculin conversion.
- To assess the role of nontuberculous mycobacterial antigens in TST conversion.
- To determine the impact of prior mycobacterial sensitivity on TST conversion rates.
Main Methods:
- 213 healthy volunteers underwent two tuberculin skin tests (5 TU PPD) one month apart.
- Nontuberculous mycobacterial antigens (PPD-G, PPD-Y, PPD-B) were administered with the first test.
- Conversion was defined as a negative to positive TST result on the second test.
Main Results:
- 14 volunteers (6.6%) showed tuberculin conversion.
- Conversion rates were significantly higher in individuals with prior nontuberculous mycobacterial sensitivity (12.6%) compared to those without (0.9%).
- Most converters (9/13) reverted to negative six months later, suggesting a temporary boosting effect.
Conclusions:
- Repeating the tuberculin skin test within a month can induce tuberculin conversion, potentially due to boosted cross-reactivity.
- Nontuberculous mycobacterial sensitivity significantly increases the likelihood of false-positive TST conversions.
- The interpretation of tuberculin conversion must consider population-specific prevalence of tuberculous and nontuberculous mycobacterial sensitization.