Mantoux Skin Test

A positive Mantoux (tuberculin) skin test is the presence of a palpable, raised induration at the injection site 48–72 hours after PPD. It suggests prior exposure to Mycobacterium tuberculosis (or prior BCG vaccination/other mycobacteria). Interpretation uses size cutoffs (commonly ≥5 mm, ≥10 mm, or ≥15 mm depending on risk). A positive test warrants further evaluation with chest X‑ray, sputum testing, or IGRA.

The Mantoux skin test (tuberculin skin test) screens for Mycobacterium tuberculosis infection. A small amount of purified protein derivative (PPD) is injected intradermally on the forearm; a trained clinician measures any induration after 48–72 hours. The size of induration, not redness, determines a positive result, which suggests latent or active TB; interpretation depends on risk factors, BCG vaccination, and immune status.

Mantoux (tuberculin) test is read as induration size in mm 48–72 hours after injection. Generally: <5 mm — negative for most; ≥5 mm — positive in high‑risk individuals; ≥10 mm — positive in moderate‑risk groups (recent immigrants, IV drug users, young children, health‑care workers); ≥15 mm — positive in people with no known risk factors. Clinical context and further tests guide diagnosis.

A positive TB skin test (Mantoux or PPD) is based on induration size, not redness. Induration ≥5 mm is positive for high‑risk people (HIV, recent TB contact, immunosuppressed); ≥10 mm for moderate‑risk groups (recent immigrants, IV drug users, healthcare workers, young children); and ≥15 mm for persons with no known risk factors. Clinical assessment and further testing (chest X‑ray, IGRA) are required.

If you test positive for TB, doctors will do more tests to see if it’s latent or active—typically a chest X‑ray and sputum tests. Active TB needs prompt multi‑drug treatment (usually a 6‑month antibiotic regimen), isolation until non‑infectious, and public‑health contact tracing. Latent TB is treated with preventive antibiotics. Regular follow‑up monitors response and drug side effects.

A Mantoux test uses a small intradermal injection on the forearm; most people feel only a brief pinch or mild stinging. Local redness, itching and a small raised bump (induration) can occur and may be tender for a few days. Significant or prolonged pain, large swelling, or systemic symptoms are uncommon—contact your healthcare provider if these occur. The test is read at 48–72 hours.