The mantoux test

MANTOUX TEST

PBL 3

BY:AZIZAH BINTI MOHAMED HALEEM

THE MANTOUX TEST The Mantoux test is the standard method of

determining whether a person is infected with Mycobacterium tuberculosis.

The local skin reaction to Tuberculin Purified Protein Derivative (PPD) injected into the skin is used to assess the individual’s sensitivity to tuberculin protein.

MANTOUX TEST

The mantoux test is given to :

• Children aged 3 months to 6 years living at high risk environments.

• Infants and children under six years of age with a history of residence or prolonged stay (more than three months) in a country of high endemic.

• There is a history of TB in a household contact in the last five years.

• Those who have had close contact with a person with known TB.

Administering the Mantoux test

Tuberculin PPD RT 23 SSI, 2 T.U./0.1 ml, solution for injection:

• 1 dose = 0.1 ml contains 0.04 microgram Tuberculin PPD.

• Store at 2°C -8°C, protected from light1ml graduated syringe fitted with a short

bevel 26G (0.45x10mm) needle

Injection site• The test is usually applied on the

middle third of the flexor surface of the forearm, as a reaction may be weaker near the wrist or the elbow joint.

• It is usually applied on the left forearm.

• Ensure adequate lighting.• Select an area of healthy skin

which is free of muscle margins, heavy hair, veins, sores, or scars.

• Only visibly dirty skin needs to be washed with soap and water

Procedure

1)Use a 1mL syringe to aspirate out 0.1 mLof PPD RT 23.

2) Inject the PPD intradermally on the volar surface of the forearm. Position the syringe at a 10-15° to the forearm and insert just below the epidermis (about 2 mm).

3)Remove the needle quickly. Do not massage or use dressing. A well-defined bleb of 6-10mm in diameter should be formed if injected correctly.If the bleb is <6mm, repeat the process 2.5cm from the first site. 4) Mark down the site, date and time of injection, both on the forearm and in patient’s record.

5) After 48 to 72 hours, read the test result by marking down the transverse diameter of induration, not erythema, by Sokal’s ballpoint method.

6) Measure the largest transverse diameter of induration and note down in millimeters(mm).

READING THE MANTOUX TEST

• The reaction should be evaluated 48-72 hours after the injection

• Only the induration, which is a hard, dense, raised formation, is measured.

• The area of erythema is not included in the measurement.

• Measure the diameter of the induration using a plastic flexible millimetre (mm) ruler.

POSITIVE PPD REACTION5 or more millimeters 10 or more millimeters 15 or more millimeters

An induration of 5 or more millimeters is considered positive for

An induration of 10 or more millimeters is considered positive for

An induration of 15 or more millimeters is considered positive for

People with HIV infection

Foreign-born persons People with no risk factors for TB

Close contacts HIV-negative persons who inject illicit drugs

People who have had TB disease before

People with certain medical conditions

People who inject illicit drugs and whose HIV status is unknown

Children younger than 4 years old

• A healthy person whose immune system is normal, induration greater than or equal to 15 mm is considered a positive skin test.

• In most cases,people who have a very small reaction or no reaction probably do not have TB infection.

• Induration of less than 2 mm, without blistering, is considered a negative skin test.

FALSE PPD REACTION

FALSE POSITIVE PPD REACTION

FALSE NEGATIVE PPD REACTION

False-Positive PPD Reactions Sometimes people who are not infected with M. tuberculosis will

have a positive reaction to the PPD tuberculin skin test.This is called a false-positive reaction.

two most common reasons for false positive PPD reactions are:-• infection with nontuberculous mycobacteria (mycobacteria other than M.

tuberculosis) • vaccination with BCG (bacillus Calmette-Gurin).

However, the reaction is more likely to be truly caused by TB infection if any of the following are true:o The reaction is largeo The person was BCG-vaccinated a long time agoo The person comes from an area of the world where TB is commono The person has been exposed to someone with infectious TB diseaseo The person's family has a history of TB disease

False-Negative Reactions 

Some people have a negative reaction to the tuberculin skin test even though they have TB infection. These are called false-negative reactions.

False-negative reactions may be caused by• Anergy• Recent TB infection (within the past 10 weeks)• Very young age (younger than 6 months old)

Type of Reaction Possible Cause People at Risk Action to Take*

False-positive

*Nontuberculous mycobacteria

*BCG vaccination

*People infected with nontuberculous mycobacteria *People vaccinated with BCG

*Evaluate for TB disease if person has TB symptoms

*Assess likelihood of true TB infection

False-negative

Anergy 

Recent TB infection 

Very young age

*HIV-infected people, other people with weakened immune systems*People infected with M. tuberculosis within the past 10 weeks*Children younger than 6 months old

*May do anergy testing 

*Retest 10 weeks after exposure to TB ended

*Retest when child is 6 months old and 10 weeks after exposure to TB ended

ADVERSE EFFECT

• anaphylactic reaction and foreign body reaction

• Slight risk of having a severe reaction to the test including swelling and redness of the arm, particularly in people who have had TB or been infected previously and in those who have previously had the BCG vaccine

• Local reactions such as regional lymphangitis and adenitis may also occur on rare occasions.

CONTRAINDICATION

• severe reaction (e.g:necrosis, blistering, anaphylactic shock, or ulcerations) to a previous TST.

reference

• http://www.immunisation.ie• http://www.hkucoi.hku.hk/TST.pdf• http://

www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm

• http://www.ncbi.nlm.nih.gov/• Medical Microbiology and

Immunology,Warren Levinson,McGraw Hill