Question

A 70-year-old man with a past history of pulmonary tuberculosis, currently on anti-tubercular therapy (ATT), presents with back pain. An MRI of the spine is performed and shows a vertebral lesion. What is the next investigation of choice to reach a definitive diagnosis?

• A. Mantoux test
• B. Biopsy
• C. Serum protein electrophoresis
• D. CT chest

Hint:

Imaging suggests; tissue confirms - the painful vertebral lesion needs a tissue diagnosis.

Answer 1

The Correct Option is B

Step 1: Frame the clinical problem.
A 70-year-old patient with a known history of pulmonary TB (already on ATT) now has back pain and an MRI-detected vertebral lesion. The key teaching point is that an MRI can suggest, but cannot definitively distinguish, the cause of a destructive vertebral lesion in an elderly patient.

Step 2: List the differentials.
In an elderly patient, a destructive spinal lesion can be tuberculous spondylitis (Pott's spine), metastasis, multiple myeloma, or primary bone tumour. Despite the TB history, malignancy must be actively excluded because TB and malignancy can coexist and have overlapping imaging features.

Step 3: Decide the next step.
Imaging (MRI/CT) characterises the lesion but is not diagnostic. To establish tissue diagnosis - to differentiate TB from malignancy and to obtain material for culture, drug-sensitivity and histopathology - a biopsy (CT-guided or open) is the definitive next investigation. It both confirms the aetiology and guides therapy.

Step 4: Why the other options are wrong.
Mantoux only indicates prior TB exposure; it is already positive in most adults from an endemic area and cannot confirm spinal TB versus malignancy. Serum protein electrophoresis screens for myeloma but is non-specific and would not characterise a focal vertebral lesion definitively. CT chest evaluates the lungs, not the painful vertebra.

Key fact: A destructive vertebral lesion needs tissue - biopsy is the definitive next step to differentiate TB from malignancy.