A patient having active infection of HIV. Mantoux skin test is performed. Which diameter of endurance considered positive or active infection of tuberculosis?

1. A

   3 mm

2. B

   7 mm

3. C

   15 mm

4. D

   11 mm

Appeared in: NORCET 3 - 2022 (Shift-2)

Explanation

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• The interpretation of the Mantoux (tuberculin skin test or TST) is based on the diameter of induration (hardened, raised area) and the patient's specific risk factors for tuberculosis (TB).
• For individuals who are severely immunocompromised, such as those with an active HIV infection, the immune response to the tuberculin antigen is weaker.
• Therefore, a smaller induration is considered significant. The official guideline for HIV-positive persons is an induration of 5 mm or greater (≥5 mm) is classified as a positive test.
• An induration of 7 mm clearly exceeds this 5 mm threshold, indicating a positive result and exposure to the TB bacterium.

Why Other Options Were Wrong

• Option A: An induration of 3 mm is below the 5 mm threshold for a positive test in an HIV-positive individual and would be considered a negative result in all risk categories.
• Option C: While 15 mm is a positive result, this option is less precise. The 15 mm cutoff is used for individuals with no known risk factors for TB. Using this as the answer would ignore the patient's specific high-risk status (HIV).
• Option D: While 11 mm is a positive result, this option is less precise. The 10 mm cutoff is typically used for individuals with moderate risk factors (e.g., healthcare workers, recent immigrants). The question specifically tests the knowledge of the lower 5 mm threshold for the high-risk HIV category.

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Clinical Relevance

• Nursing practice connection: Use the key finding related to Interpretation of Mantoux test (Tuberculin Skin Test) results in an immunocompromised patient (HIV-positive) to guide bedside assessment, documentation, and the next nursing action.
• A positive TST in an HIV-positive patient is a significant finding due to the high risk of progression from latent TB infection (LTBI) to active TB disease. It necessitates immediate further evaluation.
• Nursing Action: Following a positive TST, the nurse must assess the patient for signs and symptoms of active TB (e.g., cough, fever, night sweats, weight loss), arrange for a chest X-ray, and facilitate the collection of sputum samples for analysis.
• Patient Safety: It is crucial to understand that a positive TST does not distinguish between latent infection and active disease. Initiating TB preventive therapy for LTBI is critical in HIV-positive individuals to prevent the development of active, contagious TB.

How to Approach the Question

• First, identify the key elements in the question stem: the patient has an 'active infection of HIV' and underwent a 'Mantoux skin test'.
• The core of the question is to determine the 'positive' diameter for this specific patient population.
• Recall or look up the diagnostic criteria for interpreting the Mantoux test. Remember that the interpretation is risk-stratified.
• Identify the specific cutoff for high-risk, immunocompromised individuals, particularly those with HIV. The threshold is ≥5 mm.
• Evaluate the given options against this ≥5 mm threshold. Note that 7 mm, 11 mm, and 15 mm are all technically positive.
• In such cases, select the answer that best demonstrates knowledge of the specific threshold being tested. The 7 mm option is the smallest value that crosses the 5 mm threshold, making it the most pointed answer to test this specific knowledge.

Concept Tested & Keywords

• Concept Tested: Interpretation of Mantoux test (Tuberculin Skin Test) results in an immunocompromised patient (HIV-positive).
• Stem keywords: HIV, Mantoux skin test, tuberculosis, induration
• Lead-in keywords: considered positive
• Clinical cues: The patient's active HIV infection is the critical clinical cue, as it lowers the threshold for a positive Mantoux test.

Question ID

QlOZs1PVeLQIdMbvZ0LznG

Copy ID

Reference Book

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

E6 Medicine Harrison 22e Part 1 p. 1442-1444