**Diagnostic Method in TB is All Except**

**Core Concept**
The diagnosis of tuberculosis (TB) involves a combination of clinical evaluation, radiographic findings, and laboratory tests to detect the presence of M. tuberculosis. The bacterium can be isolated from various bodily secretions, such as sputum, blood, and cerebrospinal fluid.

**Why the Correct Answer is Right**
The correct answer is likely one of the methods listed below. The diagnosis of TB typically involves:

* **Option A:** Sputum smear microscopy: This method involves examining sputum samples under a microscope for the presence of acid-fast bacilli (AFB), which are characteristic of M. tuberculosis.
* **Option B:** Culture: This method involves growing M. tuberculosis in a controlled environment, such as a laboratory, to confirm the presence of the bacterium.
* **Option C:** GeneXpert MTB/RIF assay: This is a molecular test that detects the presence of M. tuberculosis and its resistance to rifampicin, a key antibiotic used to treat TB.

**Why Each Wrong Option is Incorrect**
* **Option D:** Chest X-ray: While chest X-rays can provide valuable information about the extent of lung damage caused by TB, they are not a diagnostic method for detecting the presence of M. tuberculosis.

**Clinical Pearl / High-Yield Fact**
Chest X-rays can show characteristic patterns of lung damage in TB, such as upper lobe infiltrates and cavitation, but a normal chest X-ray does not rule out TB.

**Correct Answer: D. Chest X-ray.**