[Skin reaction test using PPD-B]

Area of Science:

• Immunology
• Microbiology
• Public Health

Background:

• The Mycobacterium avium-M. intracellulare complex (MAC) is a group of ubiquitous environmental mycobacteria.
• Inapparent infections with MAC can occur in healthy individuals, posing diagnostic challenges.
• Skin testing with purified protein derivatives (PPDs) is a common method for assessing mycobacterial exposure.

Purpose of the Study:

• To evaluate the prevalence of inapparent MAC infections in healthy adults using skin reaction tests.
• To compare the reactivity to purified protein derivative-B (PPD-B) with standard purified protein derivatives (PPDs).
• To analyze the relationship between age and positive skin reactions to PPD-B.

Main Methods:

• A skin reaction test was performed on 379 healthy volunteers using PPD-B.
• Skin reactions were evaluated as positive (≥10 mm diameter) or significantly positive (≥ PPD reaction).
• Data was analyzed based on age groups to determine positive and significantly positive rates.

Main Results:

• The overall positive rate for PPD-B was 32.7%, increasing with age from 12.8% (18-19 years) to 51.2% (40-53 years).
• The significantly positive rate for PPD-B showed no significant increase with age.
• Positive rates for standard PPDs were considerably higher across all age groups, reaching 74.1% overall.

Conclusions:

• Skin testing with PPD-B can indicate exposure to MAC in healthy individuals, with prevalence increasing with age.
• The distinction between MAC infection and cross-reactivity with PPDs remains challenging due to overlapping reactions.
• Further research is needed to differentiate between true MAC infection and cross-reactivity in skin test results.