Which one of the following diagnostic techniques is most specific for pulmonary embolism?
**Core Concept**
The diagnosis of pulmonary embolism (PE) involves various imaging and laboratory techniques, each with its own sensitivity and specificity. **Pulmonary angiography** is considered the gold standard for diagnosing PE.
**Why the Correct Answer is Right**
Pulmonary angiography directly visualizes the pulmonary arteries, allowing for the detection of emboli. It involves injecting contrast material into the pulmonary arteries via a catheter, which then shows up on X-rays, outlining the arteries and any blockages. This method is highly specific because it directly images the site of the potential embolism.
**Why Each Wrong Option is Incorrect**
**Option A:** Is incorrect because while it may be sensitive, it lacks the specificity of directly visualizing the embolus.
**Option B:** Is incorrect as it is not as specific for PE.
**Option C:** and **Option D:** Are incorrect for similar reasons, lacking the direct visualization of pulmonary angiography.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that while **CT pulmonary angiography (CTPA)** is highly sensitive and specific, and often used due to its non-invasive nature, the gold standard for specificity in diagnosing PE, especially in cases where CTPA is inconclusive, is **pulmonary angiography**.
**Correct Answer:** D. Pulmonary angiography.