[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Diagnostic agents](https://durgical.com/en/pharmacology/classes/diagnostic-agents/) › Tuberculin purified protein derivative (PPD)

# Tuberculin purified protein derivative (PPD)

## Diagnostic agents?

Diagnostic agents

A protein extract of tuberculosis bacteria injected into the skin. A firm swelling 2–3 days later suggests infection with the TB germ.

Updated Nov 1, 2026

Also called: Mantoux test, tuberculin skin test, PPD

## Quick facts

**Group**
[Diagnostic agents](https://durgical.com/en/pharmacology/classes/diagnostic-agents/)

**Target**
Memory T cells sensitised to Mycobacterium tuberculosis (delayed, type IV hypersensitivity)

**Used for**
Testing for infection with M · Children under 5

**Key effects**
Itching or discomfort at the site

**Monitor**
Reading of induration · After a positive result

**ATC**
V04CF01

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

PPD is a standardised mixture of tuberculin proteins. Injected into the skin of someone already infected (or vaccinated with BCG, or exposed to other mycobacteria), memory T cells recognise it and call in other immune cells, which produces a firm, raised area (induration) over two to three days. The response appears only 2–8 weeks after infection. A positive test shows probable infection but does not tell latent infection from active disease.

- PPD is injected into the skin of the forearm
- Memory T cells of a sensitised person recognise it
- Immune cells gather: induration over 48–72 hours
- Induration (not redness) is measured in millimetres

## Indications

- Testing for infection with M. tuberculosis, such as in contacts of a person with infectious TB [Tuberculosis →](https://durgical.com/en/conditions/tuberculosis/)
- Screening before immunosuppression, in people with HIV and in health workers (baseline two-step testing)
- Children under 5, in whom the skin test is the recommended test

## Adverse effects

### Common

- Itching or discomfort at the site
- A firm red swelling in people who test positive

### Serious (rare, important)

- Severe local reactions: blistering, ulceration or necrosis
- Anaphylaxis (rare)

## Contraindications

- A previous severe reaction to a tuberculin skin test (necrosis, blistering, ulceration, anaphylaxis)
- Not useful when there is a documented earlier positive test or previous TB treatment
- Pregnancy, infancy and HIV are not contraindications

## Key interactions

**Live-virus vaccines (such as measles vaccine)**
Can cause a false-negative result; the test is done the same day as the vaccine or at least one month later

**BCG vaccine**
Earlier BCG can cause a false-positive result

**Immunosuppressants (high-dose corticosteroids, TNF-α antagonists)**
A weakened immune response can make a real infection test negative, so a lower cut-off is used

## What is monitored

- Reading of induration (not redness) across the forearm at 48–72 hours
- After a positive result: chest X-ray and sputum tests to look for active TB

## Administration and safety

- Given intradermally on the inner forearm with a tuberculin syringe, bevel up (Mantoux technique); a pale wheal should form.
- If no wheal forms or the depth is wrong, the test is repeated at a site well away from the first.
- A test not read within 72 hours is repeated.

## Pregnancy and breastfeeding

The skin test is safe in pregnancy and is not contraindicated.

## Nursing care

- Make sure the patient can return for the reading in 48–72 hours.
- Measure only the induration in millimetres and record the exact size.
- Ask about earlier BCG, earlier positive tests, recent live vaccines, HIV and immunosuppressive drugs.
- Explain that a negative result does not rule out TB, especially in severe illness or HIV.

## Pharmacokinetics

**Onset and duration**
Induration develops over 48–72 hours, the window in which the test is read

## Memory aid

«Feel it, don't look at it»: tuberculin is read by the firm induration you can feel at 48–72 hours, never by the redness.

## Test yourself

Think of the answer, then tap the question to see it.

## What is measured in a tuberculin skin test?

The diameter of induration in millimetres at 48–72 hours, not the redness.

## What are two causes of a false-positive tuberculin test?

Earlier BCG vaccination and infection with non-tuberculous mycobacteria.

## Why can a recent measles vaccine make the tuberculin test unreliable?

Live-virus vaccines can suppress the response and give a false negative.

## Does a positive tuberculin test mean active tuberculosis?

No: it shows probable infection; chest X-ray and sputum tests decide whether there is active disease.

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## Connections

## Related drugs 3

- [BCG vaccine (bacille Calmette-Guérin)](https://durgical.com/en/pharmacology/bcg-vaccine/)
- [Isoniazid](https://durgical.com/en/pharmacology/isoniazid/)
- [Measles vaccine](https://durgical.com/en/pharmacology/measles-vaccine/)

## Related conditions 1

- [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/)

[← Back to the class: Diagnostic agents](https://durgical.com/en/pharmacology/classes/diagnostic-agents/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Clinical Testing Guidance for Tuberculosis: Tuberculin Skin Test | Tuberculosis (TB) | CDC](https://www.cdc.gov/tb/hcp/testing-diagnosis/tuberculin-skin-test.html) (U.S. Centers for Disease Control and Prevention (CDC), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=V04CF01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/tuberculin-purified-protein-derivative/