Mantoux Test (Purified Protein Derivative) is significantly positive when the erythema measures

ESIC Nursing Officer - 2019 (Shift-2)

Medical & Surgical Nursing

Hard

Appeared in: ESIC Nursing Officer - 2019 (Shift-2)

Explanation

The Mantoux test is read by measuring the diameter of the induration (palpable, raised, hardened area), not the erythema (redness). The question stem is flawed in this regard.
An induration of 10 mm or more is considered a positive reaction for individuals with certain risk factors, such as recent immigrants from high-prevalence countries, IV drug users, and residents or employees of high-risk settings.
This range (10-14.9 mm) is commonly interpreted as a 'significant' positive result, indicating a TB infection that requires further evaluation.
It represents a clear positive finding for a large group of people, distinguishing it from doubtful or negative results.

Option A: This is also a positive result, but it is typically classified as 'strongly positive' rather than just 'significantly positive'.
Option B: This range includes results that are considered negative (less than 5 mm) and doubtful or borderline (5-9 mm). It is not a 'significantly positive' result for the general population.
Option C: This range is also considered doubtful or borderline. While a 10 mm result is a positive threshold, the range itself is not definitively 'significantly positive'.

Visual 1: Diagram - An illustration showing a forearm with a positive Mantoux test reaction. A ruler is placed across the induration (not the erythema) to measure its diameter in millimeters. This visual reinforces the correct measurement technique.
Visual 2: Chart - A flowchart or table that categorizes Mantoux test results based on induration size (≥5 mm, ≥10 mm, ≥15 mm) and lists the specific patient risk groups corresponding to each category.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Interpretation of the Mantoux (PPD) tuberculin skin test as background academic context rather than a clinical decision trigger.
A positive Mantoux test indicates that the person's body has been infected with TB bacteria. It does not differentiate between latent TB infection (LTBI) and active TB disease. Further evaluation, such as a chest X-ray and sputum analysis, is necessary to diagnose active TB.
Nurses play a crucial role in patient education, explaining that the test must be read 48-72 hours after administration and that it is the swelling (induration), not the redness (erythema), that determines the result.
Accurate measurement and interpretation are vital for appropriate follow-up and treatment, preventing the progression of latent TB to active disease and controlling the spread of infection.

How to Approach the Question

First, identify the core concept of the question, which is the interpretation of a Mantoux (PPD) test.
Critically analyze the question stem and notice the use of the word 'erythema'. Recall from your nursing knowledge that the Mantoux test is read by measuring 'induration' (hardening), not 'erythema' (redness). This is a key point and a flaw in the question.
Next, recall the standard cut-off points for a positive Mantoux test: ≥5 mm, ≥10 mm, and ≥15 mm, and understand that the interpretation depends on the patient's individual risk factors.
Evaluate the term 'significantly positive'. This suggests a result that is clearly positive but perhaps not the highest possible category.
Compare the options to the standard cut-offs. The 10 mm threshold is a widely used benchmark for a positive result in many at-risk populations. Therefore, the range '10 mm-14.9 mm' is the most logical choice for a 'significant' positive result.
Eliminate the other options: ≥15 mm is 'strongly positive', and the lower ranges are negative or doubtful for most people.

Concept Tested & Keywords

Concept Tested: Interpretation of the Mantoux (PPD) tuberculin skin test
Stem keywords: Mantoux Test, Purified Protein Derivative, PPD, erythema
Lead-in keywords: is significantly positive
Clinical cues: The question's use of 'erythema' is a critical (and incorrect) cue, as the test measures induration.

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