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Posted On : 18 May 2025

How do we perform the BCG test? What is the dose and dilution, and at what site (biceps or ventral aspect of the forearm)? How do we interpret it in relation to the child's age?

Expert Answer :

Answer Discussion :

D

Dfsa Ata

1

Tuberclin test , at ventral aspect of the forearm

5 Days ago

D

DrAhemad Pothiawala

4

BCG is used as vaccination during 1wk of life on deltoid region of left arm. BCG is no more is used as test for diagnosis of TB. It's already abandoned since long.

5 Days ago

R

Ricardo Gamaliel

4

Mantoux test or PPD test:
A standard dose of 5 tuberculin units (TU – 0.1 ml), is injected intradermally on the flexor surface of the left forearm, mid-way between elbow and wrist.
When placed correctly, injection should produce a pale wheal of the skin, 6 to 10 mm in diameter. The result of the test is read after 48–96 hours, ideally after 72 hours/3rd day. The reaction is read by measuring the diameter of induration across the forearm. Erythema should not be measured.

The measuring is performed using a scale or a rule, avoiding erythema while doing it; just focus on the papule. The results of this test must be interpreted carefully. A positive result indicates TB exposure.

5 mm or more is positive in:
An HIV-positive person
Persons with recent contacts with a TB patient
Persons with nodular or fibrotic changes on chest X-ray consistent with old healed TB

10 mm or more is positive in
Recent arrivals (less than five years) from high-prevalence countries
Injection drug users
Residents and employees of high-risk congregate settings
Mycobacteriology lab personnel
Persons with clinical conditions (e.g diabetes, leukemia, long-term steroid therapy...)
Children less than four years of age, or children and adolescents exposed to adults in high-risk categories

15 mm or more is positive in:
People who has been vaccinated
Persons with no known risk factors for TB.

A tuberculin test conversion is defined as an increase of 10 mm or more within a two-year period, regardless of age

5 Days ago

K

Kumikuyu Dickson

1

Diluted using diluent from manufacturer, o. O5ml for <1yr children 0.1ml for >1 yr children, given intrademal on the deltoid muscles on right arm

6 Days ago

A

AsadullahKhan Rawan

3

Preparation:

Reconstitute the BCG vaccine with the diluent provided by the manufacturer.

The standard dilution is usually 0.05 mL for neonates and infants under 1 year, and 0.1 mL for older children and adults.

Site of Injection:

The correct site is the intradermal layer of the left upper arm, over the deltoid (not the biceps or ventral forearm). The outer aspect is preferred to avoid confusion with other injections.

Administration:

Use a sterile 26-27 gauge needle and tuberculin syringe.

Clean the site with sterile water (not alcohol).

Inject the vaccine intradermally—a small wheal of 5-7 mm should appear if done correctly.

Interpretation in Relation to Child’s Age:

Neonates and young infants usually develop a local reaction (papule, ulcer, then scar) within 2–6 weeks.

A BCG scar indicates successful immunization.

Absence of a scar may suggest non-response; a repeat dose may be considered depending on national guidelines.

In a Mantoux test (Tuberculin Skin Test) context, prior BCG vaccination may cause mild induration, especially in younger children, but significant induration (>15 mm) still suggests TB infection, especially in older children or high-risk groups.

6 Days ago

Answer 1

The BCG test is not recommended for the diagnosis of TB now.

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