Interpretation of the Mantoux Test

Introduction

The Mantoux test, also known as the tuberculin skin test (TST), is a diagnostic tool for tuberculosis (TB). It involves intradermal injection of purified protein derivative (PPD) and subsequent measurement of induration.

Procedure

• Inject 0.1 mL of PPD tuberculin solution intradermally into the forearm.
• Mark the site and instruct the patient to avoid touching or scratching it.
• After 48-72 hours, assess the induration.

Reading and Measuring Induration

The reaction site is evaluated by measuring the diameter of the induration, not the erythema.

Classification of Results

• ≥5 mm: Considered positive in immunocompromised patients.
• ≥10 mm: Positive in high-risk individuals.
• ≥15 mm: Positive in individuals without risk factors.

Limitations

False positives may occur due to previous BCG vaccination, whereas false negatives may be seen in immunosuppressed individuals.

Conclusion

Proper interpretation is essential for accurate TB diagnosis and clinical decision-making.