**Core Concept**
TB diagnosis often involves a combination of clinical evaluation, sputum smear examination, and radiographic findings. However, in cases where the sputum smear is positive but the chest X-ray is normal or negative, the diagnosis of TB requires further confirmation to rule out other causes of cough and respiratory symptoms.

**Why the Correct Answer is Right**
The presence of a positive sputum smear is a strong indicator of TB, suggesting that the patient has a significant burden of Mycobacterium tuberculosis in their respiratory tract. However, a normal chest X-ray may not be sufficient to rule out TB, especially in the early stages of the disease. In such cases, the next step in management would be to perform an **intravenous pyelography (IVP)** or **computed tomography (CT) scan** of the chest to further evaluate the extent of lung involvement and to rule out other causes of respiratory symptoms. These imaging modalities can provide more detailed information about the lung parenchyma and can help identify subtle abnormalities that may not be visible on a standard chest X-ray.

**Why Each Wrong Option is Incorrect**
**Option A:** Performing a complete blood count (CBC) and routine biochemistry tests would not provide any specific information regarding the diagnosis of TB.

**Option B:** Administering empirical anti-TB therapy without confirmation of the diagnosis would be premature and could lead to unnecessary side effects and the development of drug-resistant TB.

**Option C:** Conducting a Mantoux test (tuberculin skin test) may be useful in some cases, but it is not the next step in management for a patient with a positive sputum smear.

**Clinical Pearl / High-Yield Fact**
In cases where the sputum smear is positive but the chest X-ray is normal or negative, it is essential to consider other causes of respiratory symptoms, such as pneumonia, bronchitis, or lung cancer, and to perform further diagnostic testing to confirm the diagnosis of TB.

**Correct Answer: D. CT scan of the chest**