Review Question - QID 103342

This patient is presenting with shortness of breath, chest pain, and mild tachycardia, and in cases such as these pulmonary embolism should be ruled out. A highly sensitive though non-specific test that can be ordered is a D-dimer - if it is negative a PE can be effectively ruled out.

The PERC criteria are a set of clinical factors that, when absent, along with a low pre-test probability, safely rule out PE in the outpatient (i.e. not emergency room, inpatient) setting. These include age > 50 years, HR > 99 per minute, O2 saturation < 95% on room air, prior history of VTE, trauma/surgery within 4 weeks, exogenous estrogen intake, unilateral leg swelling, and hemoptysis. These criteria are certainly useful in diagnosing a PE. In contrast Wells criteria are validated mostly for emergency room use. For review, the criteria include signs/symptoms of DVT/PE, PE as the most likely or tied for most likely diagnosis, pulse > 100/min, recent immobilization or surgery, history of DVT/PE, hemoptysis, and active cancer (treated within the last 6 months). While the PERC and Wells criteria appear similar, PERC criteria consider more risk factors to generate a more rigorous negative predictive value.

Incorrect Answers:
Answer 1: A CT with IV contrast is a valuable tool in diagnosing PE. This is typically a confirmatory test in cases of PE and it is highly sensitive and specific. The CT is typically not used in cases of renal failure due to the IV contrast.
Answer 2: The V/Q scan is another confirmatory test that can be used to diagnose PE, but it is less commonly used than the CT-PE study. This is the preferred confirmatory test in patients who have renal failure and who can't tolerate IV contrast.
Answer 3: A chest radiograph can show some abnormalities in patients with PE (such as Westermark's sign), but it is not typically the initial study in suspected PE and is neither sensitive nor specific.
Answer 4: In a patient who likely has a DVT (e.g. recent immobilization, unilateral swollen leg) a DVT could make the diagnosis of PE as it is a very specific test. The problem with ultrasound is that it is not very sensitive as most DVT's can occur in the pelvic veins or in locations other than the lower extremities.