From the Guidelines
For a patient presenting with chest pain, tachycardia, and tachypnea with suspicion of atypical pulmonary embolism (PE), the correct initial diagnostic test would be D-Dimer. D-Dimer is the most appropriate first step because it has high sensitivity for PE and serves as an excellent rule-out test, as supported by the American College of Physicians' clinical guidelines committee 1. A negative D-Dimer in a patient with low to intermediate clinical probability effectively excludes PE, avoiding unnecessary radiation exposure from further imaging. If the D-Dimer is positive, then further diagnostic testing such as CT pulmonary angiography would be warranted. Some key points to consider in the diagnostic approach include:
- Using validated clinical prediction rules to estimate pretest probability in patients suspected of having acute PE.
- Applying the Pulmonary Embolism Rule-Out Criteria (PERC) to patients with low pretest probability to determine if further testing is needed.
- Utilizing age-adjusted d-dimer thresholds for patients older than 50 years to improve specificity without significantly compromising sensitivity.
- Reserving imaging studies, such as CT pulmonary angiography, for patients with high pretest probability of PE or those with positive d-dimer results. While ECG may show classic findings like S1Q3T3 pattern, right bundle branch block, or T-wave inversions in anterior precordial leads in PE, these findings lack sensitivity and specificity. Similarly, chest X-ray is often normal in PE or may show nonspecific findings. The clinical presentation of chest pain, tachycardia, and tachypnea creates enough suspicion for PE that warrants D-Dimer testing first, even without classic risk factors like immobility or DVT, as PE can still occur in patients without obvious predisposing factors 1. It's also important to note that the specificity of an elevated d-dimer level may be lower in inpatients than in outpatients or ED patients, probably due to comorbidities in the inpatient population 1. However, d-dimer testing as an initial step for inpatients suspected of having PE is still appropriate because it remains highly sensitive for the disease and a normal level, in combination with appropriate pretest risk stratification, can prevent unnecessary imaging 1. Given the evidence, D-Dimer is the recommended initial diagnostic test for patients with suspected atypical PE, given its high sensitivity and ability to rule out PE in patients with low to intermediate pretest probability, thus guiding further management and reducing unnecessary testing and potential harm to patients.
From the Research
Initial Diagnostic Test for Suspected Atypical Pulmonary Embolism
The most appropriate initial diagnostic test for a patient presenting with chest pain, tachycardia, and tachypnea, with a suspected atypical Pulmonary Embolism (PE) and normal findings on physical examination, including no signs of Deep Vein Thrombosis (DVT), is a topic of discussion in several studies 2, 3, 4, 5, 6.
D-Dimer Test
- The D-dimer test is a widely used screening test for PE, and a normal D-dimer level can help rule out PE in patients with a low clinical pretest probability 4.
- However, a normal D-dimer level does not completely rule out PE, as seen in the case study where a patient with a normal D-dimer level was diagnosed with PE 2.
- The study by 5 found that the absolute level of D-dimers, particularly > 2.0 mg/l, is a strong predictor of PE.
Clinical Decision Rules and Imaging Studies
- Clinical decision rules, such as the Wells and Geneva scores, can be used in conjunction with D-dimer testing to risk-stratify patients and guide further diagnostic testing 3, 6.
- Imaging studies, such as computed tomography pulmonary angiography (CTPA) and ventilation-perfusion (V/Q) single-photon emission computed tomography (SPECT), are essential for confirming the diagnosis of PE 3.
- The study by 6 found that a modified ECG score can be used to estimate the pretest probability of PE and may be more accurate than the Wells and Geneva scores in certain cases.