The importance of early erythematous reaction in purified protein derivative skin testing

Area of Science:

• Pediatric Infectious Diseases
• Diagnostic Immunology
• Mycobacterial Infections

Background:

• Tuberculosis diagnosis in children often relies on skin testing.
• The standard interpretation of purified protein derivative (PPD) skin testing involves measuring induration at 48 hours.
• Early assessment of PPD reactions may offer faster diagnostic insights.

Purpose of the Study:

• To evaluate the diagnostic utility of the early (6-hour) erythematous reaction in PPD skin testing for pediatric tuberculosis.
• To compare the efficacy of the 6-hour erythematous reaction with the traditional 48-hour induration measurement.

Main Methods:

• Purified protein derivative (PPD) skin testing was administered to 64 children with pulmonary tuberculosis and 49 healthy controls.
• Erythematous reactions were assessed at 6 hours post-application.
• Induration measurements were taken at 48 hours for comparison.

Main Results:

• A 6-hour erythematous reaction of ≥5 mm demonstrated 76% sensitivity and 85% specificity for active tuberculosis.
• This early reaction also showed 83% sensitivity in predicting the development of a ≥10 mm induration at 48 hours.
• The predictive values for the 6-hour reaction were 87% positive and 73% negative.

Conclusions:

• The 6-hour early erythematous reaction following PPD testing is a valuable and potentially faster indicator for diagnosing pulmonary tuberculosis in children.
• This early assessment provides diagnostic information comparable to the standard 48-hour induration measurement.
• The findings support considering early reading of PPD skin tests in pediatric tuberculosis diagnosis.