In a patient with high clinical suspicion of pulmonary thromboembolism, the best investigation would be?
**Core Concept**
In patients with suspected pulmonary thromboembolism (PTE), a rapid and accurate diagnostic approach is crucial to prevent further complications. The investigation of choice should ideally be non-invasive, widely available, and have high sensitivity and specificity for diagnosing PTE.
**Why the Correct Answer is Right**
Computed Tomography Pulmonary Angiography (CTPA) is the best investigation for suspected PTE due to its high sensitivity (approximately 83-100%) and specificity (approximately 96-100%) in detecting pulmonary emboli. CTPA allows for the visualization of the pulmonary arteries and the detection of emboli, which is essential for diagnosing PTE. The use of contrast-enhanced CT scans also enables the identification of other potential complications, such as pulmonary infarction or hemorrhage.
**Why Each Wrong Option is Incorrect**
**Option A:** Chest X-ray is not the best investigation for suspected PTE as it lacks sensitivity and specificity for detecting pulmonary emboli. While a chest X-ray may show signs suggestive of PTE, such as the Westermark sign or Hampton's hump, it is not a reliable diagnostic tool.
**Option B:** Ventilation-Perfusion (V/Q) scan is an alternative diagnostic tool for PTE, particularly in patients with contraindications to CT scans or in those with a high risk of radiation exposure. However, it is not the best investigation for suspected PTE due to its lower sensitivity and specificity compared to CTPA.
**Option C:** Pulmonary angiography is a more invasive diagnostic tool that involves injecting contrast material directly into the pulmonary arteries. While it is highly sensitive and specific for diagnosing PTE, it is typically reserved for cases where CTPA is inconclusive or in patients with a high suspicion of PTE who require a definitive diagnosis.
**Clinical Pearl / High-Yield Fact**
In patients with suspected PTE, it is essential to consider the Wells score, which is a clinical prediction rule that helps estimate the probability of PTE. The score takes into account factors such as clinical history, physical examination findings, and laboratory results to guide the diagnostic approach.
**Correct Answer:** C. Pulmonary angiography