Time required to read mantoux, test is?

HPSSSB Staff Nurse - 2016

Medical & Surgical Nursing

Easy

Appeared in: HPSSSB Staff Nurse - 2016

Explanation

The Mantoux test relies on a delayed-type (Type IV) hypersensitivity reaction, which involves T-cells and macrophages.
This immune response takes time to develop, with the peak reaction occurring between 48 and 72 hours after the injection.
The peak reaction is visible as a hardened, raised area called induration.
Reading the test within this specific 48-72 hour window is crucial for an accurate measurement of the body's immune response to the tuberculin antigen.

Option A: Reading the test at 12-24 hours is too early. The delayed hypersensitivity reaction has not had sufficient time to develop, which can lead to a false-negative result even if the person is infected.
Option B: While the reaction is developing, reading between 24-48 hours is still premature. The induration may not have reached its maximum size, potentially causing an underestimation of the reaction and a false-negative reading.
Option D: Reading the test after 72 hours is too late. The induration from the immune reaction may have already started to decrease in size or disappear, leading to an inaccurate measurement and a potential false-negative result.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Tuberculin Skin Test (Mantoux Test) Interpretation as background academic context rather than a clinical decision trigger.
Accurate timing and reading of the Mantoux test are critical for the diagnosis of latent tuberculosis infection (LTBI), which guides clinical decisions on initiating preventive therapy.
Nurses play a key role in patient education, emphasizing the importance of returning for the reading within the 48-72 hour window to ensure test validity and avoid the need for a repeat procedure.
A positive TST result indicates that the person's body was infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to active TB disease.

How to Approach the Question

Identify the core question, which asks for the specific time frame to read a Mantoux test.
Recognize this as a factual recall question based on a standard clinical procedure.
Recall the immunological basis of the test: it is a delayed-type hypersensitivity reaction.
Understand that the term 'delayed' implies the reaction takes a couple of days to reach its peak.
Eliminate the shorter time frames (12-24 and 24-48 hours) as too early and the longer time frame (>72 hours) as too late.
Select the option that corresponds to the known peak reaction time for a tuberculin test, which is 48-72 hours.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart B (pp 202-403 of 604) p. 25-27

E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 257-259