Two-stage skin testing for tuberculosis in a domiciliary population.

Area of Science:

• Infectious Diseases
• Public Health
• Immunology

Background:

• Tuberculosis (TB) remains a significant public health concern, particularly in congregate settings like long-term care facilities.
• Accurate screening for latent TB infection is essential for timely intervention and preventing disease transmission.
• Previous TB screening methods may have limitations in identifying all exposed individuals in specific populations.

Purpose of the Study:

• To evaluate the effectiveness of two-stage skin testing for tuberculosis in residents of a domiciliary unit.
• To determine the prevalence of tuberculosis exposure in this specific patient population.
• To assess the impact of the duration of residency on tuberculosis skin test conversion rates.

Main Methods:

• Conducted two-stage tuberculosis skin testing using purified protein derivative (PPD) on 618 residents.
• Included Candida and mumps as control antigens for skin testing.
• Administered a second PPD test to individuals with less than 10 mm induration after the initial test.

Main Results:

• 50.9% of residents showed evidence of tuberculosis exposure via skin testing.
• A booster response was observed in 19.2% of patients receiving a second PPD test.
• Second test conversion rates were significantly higher in residents with longer stays (3-6 months) compared to shorter stays (<1 month).

Conclusions:

• Two-stage purified protein derivative (PPD) testing is recommended for all residents in chronic care facilities, even those with a negative initial test.
• Identifying tuberculosis exposure through skin testing is vital for initiating preventive measures.
• Isoniazid (INH) prophylaxis should be considered for residents with significant Mantoux reactions in chronic care settings.