The nurse determines that a Mantoux tuberculin skin test is positive. To most accurately diagnose tuberculosis, the nurse plans to consult with the physician to follow up the skin test with a?

Appeared in: DHS 2018 shift 1st

Explanation

A sputum culture is the gold standard for diagnosing active pulmonary tuberculosis.
It provides definitive evidence by isolating and identifying live Mycobacterium tuberculosis from a clinical specimen.
This method distinguishes active disease, which requires treatment, from latent infection, where bacteria are present but not causing illness.
Unlike imaging tests, which show structural changes, culture confirms the presence of the causative organism.
Results from culture also enable drug susceptibility testing to guide effective treatment, especially in cases of suspected drug resistance.

Option A: A chest X-ray is a screening tool, not a definitive diagnostic test. While it can show abnormalities consistent with TB (like infiltrates or cavities), these findings are not specific and can be caused by other lung diseases.
Option C: A Complete Blood Count (CBC) is a non-specific test. It measures general markers of health, inflammation, and infection (like white blood cell count) but cannot identify the specific pathogen causing an illness like tuberculosis.
Option D: A CT scan, while more sensitive than a chest X-ray for detecting lung abnormalities, is still an imaging test. It cannot confirm the presence of M. tuberculosis bacteria, which is required for a definitive diagnosis.

Clinical Relevance

Nursing practice connection: Knowing Definitive diagnosis of active tuberculosis following a positive screening test helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses play a crucial role in patient education regarding the difference between latent TB infection and active TB disease, explaining why further testing is necessary after a positive skin test.
Proper collection of sputum specimens is a key nursing responsibility. The nurse must instruct the patient on how to produce a deep cough specimen (not just saliva) to ensure the sample is adequate for culture.
What if? If the patient is unable to produce a sputum sample (e.g., a child or an elderly patient), the nurse should anticipate the need for alternative collection methods like sputum induction or bronchoscopy with bronchoalveolar lavage.

How to Approach the Question

First, identify the core of the question: it asks for the 'most accurate' test to 'diagnose' tuberculosis.
Recognize that a positive Mantoux test only indicates exposure, not active disease. The key is to find the test that confirms an active infection.
Analyze the options. Differentiate between screening/imaging tests (Chest X-ray, CT scan) and microbiological tests (Sputum culture). A CBC is a general, non-specific test.
Recall that a 'diagnosis' of an infectious disease is most accurately made by identifying the causative organism.
Compare the options based on this principle. While X-ray and CT show effects on the lungs, only the sputum culture directly detects the M. tuberculosis bacteria.
Conclude that the sputum culture is the definitive or 'gold standard' test, making it the most accurate choice.

Concept Tested & Keywords

Concept Tested: Definitive diagnosis of active tuberculosis following a positive screening test.
Stem keywords: Mantoux tuberculin skin test, positive, diagnose tuberculosis, follow up
Lead-in keywords: most accurately
Clinical cues: A positive Mantoux test necessitates further investigation to differentiate between latent and active TB.

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E6 Medicine Harrison 22e Part 1 p. 1433-1435

E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart B (pp 202-403 of 604) p. 23-25

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

Practise the full DHS 2018 shift 1st

Attempt every question from this paper in a timed mock, then review the full solution for each one.