## **Core Concept**
The core concept being tested here is the appropriate diagnostic approach for a patient with a suspected prostatic nodule, which could indicate prostate cancer or other prostate pathology. The best investigation should ideally be able to distinguish between benign and malignant conditions.

## **Why the Correct Answer is Right**
The correct answer, **. Prostate Specific Antigen (PSA) and Digital Rectal Examination (DRE) followed by Transrectal Ultrasound (TRUS) guided biopsy**, is considered the gold standard for diagnosing prostate cancer.
- **PSA** is a tumor marker that can be elevated in prostate cancer, though not specific to cancer.
- **DRE** allows for the assessment of the prostate gland's texture, size, and any irregularities.
- **TRUS-guided biopsy** provides a histological diagnosis, which is essential for confirming cancer and assessing its aggressiveness.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While an **X-ray** might show advanced disease (e.g., bone metastases), it is not specific or sensitive for early prostate cancer or nodule evaluation.
- **Option B:** **CT Scan** can help with staging but is not the best initial investigation for evaluating a prostatic nodule due to its lower sensitivity for early prostate cancer compared to TRUS-guided biopsy.
- **Option C:** **MRI** can be useful for staging and in some cases for guiding biopsies but is generally not the first line for initial evaluation of a prostatic nodule.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the combination of **PSA testing** and **DRE** is crucial for early detection of prostate abnormalities. However, the definitive diagnosis of prostate cancer relies on **histopathological examination** of tissue obtained through biopsy, typically guided by **TRUS**.

## **Correct Answer:** . Prostate Specific Antigen (PSA) and Digital Rectal Examination (DRE) followed by Transrectal Ultrasound (TRUS) guided biopsy