Interpretation of the Mantoux Test
Procedure and Administration of the Mantoux Test
The Mantoux test is a crucial screening tool for tuberculosis infection. It involves an intradermal injection and subsequent measurement of skin induration to determine TB exposure.
Interpretation of the Mantoux Test
Procedure and Administration of the Mantoux Test
The Mantoux test, also known as the tuberculin skin test (TST), is a diagnostic tool used to identify latent tuberculosis (TB) infection. This test involves the intradermal injection of purified protein derivative (PPD) tuberculin, followed by measuring the induration after 48 to 72 hours.
Procedure
- Preparation: The skin is cleansed with alcohol, usually on the volar aspect of the forearm.
- Injection: 0.1 mL of PPD tuberculin is injected intradermally using a 27-gauge needle, forming a visible wheal of approximately 6-10 mm.
- Assessment: Induration is measured at 48-72 hours using the ballpoint method.
Interpretation of Results
- Positive (>5 mm in high-risk groups): Indicates probable TB infection and requires further evaluation.
- Negative (<5 mm): Usually suggests no infection, though false negatives may occur in immunocompromised individuals.
- Intermediate (5-10 mm): Requires further clinical correlation, particularly in patients with TB risk factors.
Limitations and Considerations
False-positive and false-negative results can occur due to BCG vaccination, improper administration, or immunosuppression. Additional diagnostic tests, such as interferon-gamma release assays (IGRAs), may be required for confirmation.
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