What is the Tuberculin Test for the diagnosis of TB called?

Appeared in: Raj. CHO -2020

Explanation

The Mantoux test is the standard tuberculin skin test (TST) used to screen for exposure to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB).
The test involves the intradermal injection of a small, standardized amount of tuberculin Purified Protein Derivative (PPD).
A delayed hypersensitivity reaction, which appears as a firm, raised, swollen area called an induration, indicates exposure to the TB bacterium.
The result is read by measuring the diameter of the induration in millimeters 48 to 72 hours after the injection.

Option A: The Schick test is used to determine susceptibility to diphtheria, not tuberculosis. It involves injecting diphtheria toxin into the skin.
Option C: The VDRL (Venereal Disease Research Laboratory) test is a screening test for syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum.
Option D: ELISA (Enzyme-Linked Immunosorbent Assay) is a general laboratory technique used to detect the presence of antibodies or antigens in a sample. While it is used for many infectious diseases like HIV, it is a method, not the specific name for the tuberculin skin test.

Visual 1: Infographic - A diagram showing the correct intradermal injection technique for the Mantoux test on the forearm, highlighting the formation of a wheal.
Visual 2: Image - A close-up photograph demonstrating how to measure the induration of a positive Mantoux test result with a ruler, clearly distinguishing it from surrounding redness.

Clinical Relevance

Nursing practice connection: Use the key finding related to Diagnostic Tests for Tuberculosis to guide bedside assessment, documentation, and the next nursing action.
Correct administration and interpretation of the Mantoux test are fundamental nursing skills. It is crucial to measure the induration (the palpable, raised, hardened area) and not the erythema (redness) to ensure an accurate reading.
Patient education is a key nursing role. Nurses must instruct patients to not scratch or cover the site and to return within 48-72 hours for the reading, as a reading outside this window is invalid.
A history of BCG (Bacille Calmette-Guérin) vaccination can cause a false-positive Mantoux test. Nurses should be aware of this and understand that for such patients, an Interferon-Gamma Release Assay (IGRA) blood test may be preferred as it is not affected by prior BCG vaccination.

How to Approach the Question

First, identify the key terms in the question: 'Tuberculin Test' and 'diagnosis of TB'.
This is a factual recall question that requires knowledge of common diagnostic tests.
Systematically evaluate each option. Recall or deduce the purpose of each test.
Option A, Schick test, is for diphtheria.
Option B, Mantoux Test, is the specific name for the tuberculin skin test.
Option C, VDRL, is for syphilis.

Concept Tested & Keywords

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