Which is the confirmative test of TB?

Central Institute of Psychiatry - 9 July 2022

Medical & Surgical Nursing

Easy

Appeared in: Central Institute of Psychiatry - 9 July 2022

Explanation

Sputum culture is considered the 'gold standard' for diagnosing active pulmonary tuberculosis.
It provides definitive proof by isolating and growing the live Mycobacterium tuberculosis organism from a patient's sample.
Crucially, culture allows for drug susceptibility testing (DST), which guides the selection of effective antibiotic therapy and helps combat drug resistance.

Option B: A chest X-ray can show findings suggestive of TB (like cavities or infiltrates), but these are not specific. Other conditions, such as pneumonia or lung cancer, can have similar appearances.
Option C: The Mantoux test (Tuberculin Skin Test) only indicates if a person has been exposed to TB bacteria and has developed an immune response. It cannot differentiate between a latent infection (where the bacteria are dormant) and active, contagious disease.
Option D: Pulmonary Function Tests (PFTs) measure lung mechanics, such as volume and airflow. They assess the functional impact of a lung disease but do not identify the underlying cause or pathogen.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diagnosis of Tuberculosis as background academic context rather than a clinical decision trigger.
A definitive diagnosis via sputum culture is essential before starting the long course of anti-tubercular therapy (ATT) to avoid unnecessary treatment and side effects.
Confirming the diagnosis and performing drug susceptibility testing is a critical public health function to prevent the spread of drug-resistant TB (DR-TB), which is harder and more expensive to treat.
What if? If a patient has clinical symptoms and a chest X-ray highly suggestive of TB but the initial sputum smears are negative, the nurse should anticipate that the physician will still send a sputum sample for culture and possibly a rapid molecular test (like CB-NAAT/GeneXpert), as these are more sensitive than smear microscopy.

How to Approach the Question

First, identify the core of the question: it asks for a 'confirmative' test. This implies a test that provides a definitive, unquestionable diagnosis.
Analyze the options based on their diagnostic role. Think about what each test actually measures.
Sputum culture looks for the actual bacteria. Chest X-ray looks for shadows/lesions. Mantoux test looks for an immune reaction. PFT measures lung function.
Recognize the difference between a screening test (like Mantoux, which identifies potential cases) and a confirmatory test (which proves the disease).
Conclude that directly identifying the causative organism (M. tuberculosis) through culture is the only way to be 100% certain, making it the confirmatory test.

Concept Tested & Keywords

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