# Mantoux Test (Tuberculin Skin Test)

## Overview

This module describes how to interpret a Mantoux test. Although often associated with false negatives and positives, the Mantoux test is part of the workup for suspected TB.

## Indications

## Contraindications

## Patient information and consent

### How do I explain this procedure?

“After we gave your child the injection to test for TB, we asked you to wait 2-3 days and then come back so that we can read the result.”

### What can my patient expect?

“I am going to measure with a ruler how large the spot on your child’s arm is. It will not hurt at all. From this I will be able to tell you if your child has TB or needs further testing for TB.”

### What is my patient’s role?

“Please hold your child’s arm steady for me while I measure.”

## Procedure

Follow medical asepsis without gloves.

## Interpretation

When is a Mantoux test positive?

- Induration ≥ 5 mm is positive in HIV positive, malnourished, or severely ill children.
- Induration ≥ 10 mm is positive in all children.

What does a positive test result mean?

- A positive result combined with a history of TB symptoms, a TB contact or a suggestive chest X-ray, indicates active TB disease and requires treatment.
- A positive result without any of the above may indicate latent TB infection. These patients should receive TB prophylaxis.

A false positive may occur if:

What does a negative test result mean?

- A negative result does not rule out latent TB infection or active TB disease.
- In suggestive cases with a negative Tuberculin Skin Test result, you may still need to do further TB workup (often some combination of a chest X-ray, gastric washings, sputum collection, and/or abdominal ultrasound) and you may also repeat the Tuberculin Skin Test after 8 weeks.

A false negative may occur if:

## Troubleshooting

The patient presented too early to read the test.

Advise the patient to return in the 48-72 hour window. The results cannot be read yet.

The patient presented too late to read the test.

Schedule a repeat test as soon as possible (you may do it on the same day).

The patient is due for a live-virus vaccine and needs a TB test.

Do the test and administer the vaccine on the same day, or administer the vaccine now and perform the TB test a month later.

## References