Interpretation of the Mantoux Test
Principles and Purpose of the Mantoux Test
The Mantoux test is a critical diagnostic tool for detecting tuberculosis infection. It involves a skin reaction to PPD injection and is interpreted based on induration size and risk factors.
Interpretation of the Mantoux Test
Principles and Purpose
The Mantoux test, also known as the Tuberculin Skin Test (TST), is a diagnostic tool used to detect tuberculosis (TB) infection. It involves an intradermal injection of purified protein derivative (PPD) and measuring the resulting induration after 48-72 hours.
Procedure
- Step 1: A small amount (0.1 mL) of PPD is injected into the forearm.
- Step 2: The site is inspected after 48-72 hours to measure the size of the raised induration.
- Step 3: The results are interpreted based on the size of the induration and patient risk factors.
Interpretation of Results
| Induration Size | Interpretation | Risk Factors |
|---|---|---|
| >5mm | Positive for high-risk groups | HIV-positive, recent TB exposure |
| >10mm | Positive for moderate-risk groups | Healthcare workers, immigrants, IV drug users |
| >15mm | Positive for low-risk individuals | No known risk factors |
Limitations and Next Steps
False positives may occur due to prior BCG vaccination, while false negatives can result from immunosuppression. A positive Mantoux test does not confirm active tuberculosis—it requires further diagnostic tests such as chest X-ray and sputum analysis.
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