Interpretation of the Mantoux Test

Procedure for Administering the Test

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

Step-by-Step Procedure

• Cleanse the forearm with an alcohol swab.
• Inject 0.1 mL of PPD intradermally using a tuberculin syringe.
• Ensure the formation of a small wheal (6-10 mm) at the injection site.
• Advise the patient to avoid scratching or covering the site.
• Assess the reaction after 48-72 hours.

Interpretation of Results

Induration Size	Interpretation
0-4 mm	Negative
5-9 mm	Doubtful - Requires clinical correlation
≥10 mm	Positive - Suggestive of TB infection

Limitations & Considerations

False-positive and false-negative results may occur due to factors like prior BCG vaccination, immunosuppression, or improper administration.