Why Is Imaging Not Indicated for Suspected PE with Low Risk and a Negative D-dimer?

A 45-year-old man with no significant medical history presents to the emergency department on a Tuesday afternoon with two days of vague, non-pleuritic chest discomfort. His vital signs are stable, and his oxygen saturation is 99% on room air. You calculate a Wells’ score of 0, placing him in the low pretest probability category for pulmonary embolism (PE). Following established diagnostic algorithms, you order a high-sensitivity D-dimer test, which returns negative. The immediate question is whether to stop the workup or proceed to imaging “just to be safe.” For this specific clinical scenario—low or intermediate pretest probability of PE with a negative D-dimer—the American College of Radiology (ACR) rates advanced imaging studies like CT pulmonary angiography as Usually not appropriate. This article details the evidence-based rationale for confidently ruling out PE without imaging in this common clinical presentation.

Who Fits This Clinical Scenario?

This guidance applies to a well-defined patient population where a PE workup has been initiated. The two key inclusion criteria are:

1. Low or Intermediate Pretest Probability: The patient’s risk of having a PE, based on clinical signs, symptoms, and risk factors, has been formally assessed as low or intermediate. This is typically determined using a validated clinical decision rule such as the Wells’ score or the revised Geneva score. This step is crucial, as the utility of D-dimer testing is highest in this population.
2. Negative D-dimer Result: A quantitative, high-sensitivity D-dimer assay has been performed and the result is negative (below the established cutoff, which may be age-adjusted). The negative predictive value of this test in a low-risk population is extremely high.

Conversely, this workflow is not appropriate for patients who fall into other ACR variants. Key exclusions include:

• High Pretest Probability: Patients with a high Wells’ or Geneva score should typically proceed directly to imaging, as a D-dimer test is not sufficient to rule out PE in this group.
• Positive D-dimer Result: A patient with a low or intermediate pretest probability but a positive D-dimer requires further evaluation, usually with imaging.
• Pregnant Patients: The workup for suspected PE in pregnancy follows a specialized algorithm due to physiologic changes and the need to minimize fetal radiation exposure.

What Diagnoses Are You Working Up in This Scenario?

When a patient presents with symptoms like chest pain or shortness of breath, the initial differential diagnosis is broad. The primary goal of the PE workup is to rule in or rule out this life-threatening condition. However, many other conditions present similarly.

Pulmonary Embolism (PE): This is the anchor diagnosis being investigated. Symptoms can range from pleuritic chest pain and dyspnea to syncope. The combination of a low pretest probability score and a negative D-dimer makes this diagnosis exceptionally unlikely, with a post-test probability well below the accepted testing threshold of 1-2%.

Musculoskeletal Chest Pain: This is one of the most common causes of chest pain in the outpatient and emergency settings. It can be caused by costochondritis, muscle strain, or rib injury. The pain is often reproducible on palpation, a feature not typical of PE.

Gastroesophageal Reflux Disease (GERD) or Esophageal Spasm: Acid reflux can cause significant substernal, burning chest pain that can mimic cardiac or pulmonary conditions. A thorough history can often elicit associated symptoms like a sour taste, post-meal worsening, or relief with antacids.

Anxiety or Panic Attack: The somatic symptoms of anxiety can be profound, including chest tightness, shortness of breath, tachycardia, and a sense of impending doom. These symptoms overlap significantly with PE, but the objective data from the risk score and D-dimer help differentiate.

After a negative D-dimer in a low-risk patient, the clinical focus should pivot away from PE and toward these alternative, and now far more probable, diagnoses.

Why Is No Imaging Study Recommended for This Presentation?

In the setting of low or intermediate pretest probability and a negative D-dimer, the ACR Appropriateness Criteria panel on cardiac imaging has determined that all forms of diagnostic imaging for PE are Usually not appropriate. This includes CT pulmonary angiography (CTA), V/Q scans, and even lower extremity ultrasound. The rationale is grounded in the principles of diagnostic test thresholds and risk-benefit analysis.

The combination of a low clinical probability and a negative high-sensitivity D-dimer provides powerful evidence against the presence of venous thromboembolism (VTE). The post-test probability of PE in this scenario is exceedingly low, often less than 1%. At this level, the potential harms of imaging—radiation exposure, contrast-induced nephropathy, allergic reactions, and the costs associated with false positives—outweigh the negligible chance of detecting a clinically significant PE.

Let’s examine why specific alternatives are rated poorly for this scenario:

• CTA pulmonary arteries with IV contrast: This is the gold standard for diagnosing PE in many other scenarios, but here it is rated Usually not appropriate. The primary reason is the unnecessary radiation exposure (ACR Relative Radiation Level ☢☢☢, corresponding to 1-10 mSv) and contrast risks for a diagnosis that has already been effectively excluded.
• V/Q scan lung: Also rated Usually not appropriate, a V/Q scan involves radiation (ACR RRL ☢☢☢, 1-10 mSv) and is less specific than CTA. It is generally reserved for patients with a contraindication to iodinated contrast, but it offers no benefit when the pre-imaging probability of PE is already vanishingly small.
• US duplex Doppler lower extremity: While this study has no radiation (ACR RRL O, 0 mSv), it is also rated Usually not appropriate. Its purpose is to detect deep vein thrombosis (DVT), the source of most PEs. However, a negative D-dimer makes a significant DVT highly improbable. Ordering this study would be an indirect and low-yield approach to a PE workup that should have already concluded.

The core principle is that the diagnostic algorithm has reached a safe and logical stopping point. Proceeding to imaging introduces risks without a commensurate clinical benefit.

What’s Next After a Negative D-dimer? Downstream Workflow

The most important next step in this clinical workflow is to formally conclude the pulmonary embolism workup. This decision should be clearly documented in the patient’s chart, along with the pretest probability score and the negative D-dimer result. The downstream workflow then pivots entirely to addressing the patient’s symptoms through the lens of the remaining, more likely, differential diagnoses.

• If the workup is negative: The clinician should communicate clearly with the patient, explaining that a dangerous blood clot in the lungs has been safely ruled out. This reassurance is a critical part of the therapeutic intervention. The focus can then shift to identifying the true cause of their symptoms. Is the pain reproducible on palpation, suggesting a musculoskeletal origin? Is it related to meals, suggesting GERD?
• Re-evaluating the differential: With PE off the table, the clinician can pursue a more focused history and physical exam. This may lead to a trial of non-steroidal anti-inflammatory drugs (NSAIDs) for suspected costochondritis or a proton-pump inhibitor (PPI) for suspected GERD.
• Appropriate disposition: Most of these patients can be safely discharged from the emergency department or managed in an outpatient setting with instructions for follow-up with their primary care physician. Clear return precautions should be given, advising the patient to seek re-evaluation for any new, worsening, or changing symptoms.

This represents a successful diagnostic outcome: a dangerous condition was ruled out efficiently and safely, avoiding the costs and risks of unnecessary advanced imaging.

Pitfalls to Avoid (and When to Get Help)

While the PE rule-out algorithm is robust, several pitfalls can lead to diagnostic errors or unnecessary testing. First, avoid ordering a D-dimer in very low-risk patients who are “PERC-negative” (meeting all criteria of the Pulmonary Embolism Rule-out Criteria), as this can lead to false-positive results and a cascade of unnecessary imaging. Second, ensure you are using a high-sensitivity D-dimer assay; the algorithm’s safety is contingent on the test’s high negative predictive value. Third, resist the urge to order imaging “just in case” after the algorithm is complete. This undermines evidence-based practice and exposes the patient to needless risk. If the clinical picture is truly incongruous with the negative workup—for example, the patient has worsening hypoxia or vital sign instability—it is time to stop, reassess the patient from scratch, and consider consulting a specialist like a pulmonologist or cardiologist.

Related ACR Topics and Tools

For a comprehensive overview of imaging recommendations across all clinical presentations of suspected PE, please see our parent guide. For further exploration of ACR guidelines, imaging techniques, and radiation safety, the following GigHz resources are available:

• Suspected Pulmonary Embolism: ACR Appropriateness Decoded
• ACR Appropriateness Criteria Lookup
• Imaging Protocol Library
• Radiation Dose Calculator

Frequently Asked Questions

What if the patient is very anxious about a PE and wants a CT scan anyway?

This is a common situation that calls for shared decision-making. The best approach is to clearly explain the rationale: the combination of their low-risk features and the negative blood test makes a dangerous clot extremely unlikely. You can then quantify the risks of the CT scan, including radiation exposure and potential contrast reactions, to help them understand that the test carries more potential for harm than benefit in their specific case.

Does this guidance apply if I used the PERC rule to determine the patient is low risk?

Yes. The Pulmonary Embolism Rule-out Criteria (PERC) is designed to identify a very low-risk cohort in whom no further testing is needed—not even a D-dimer. If a patient is PERC-negative, the PE workup should stop. This ACR scenario applies to patients who were not PERC-negative and proceeded to D-dimer testing, which was negative.

Is there any role for a lower extremity ultrasound in this scenario?

According to the ACR, a lower extremity duplex ultrasound is ‘Usually not appropriate’ in this specific scenario. A negative D-dimer has a very high negative predictive value for both deep vein thrombosis (DVT) and PE. Therefore, searching for a DVT after a negative D-dimer in a low-risk patient is not a recommended part of the algorithm.

What if my institution’s D-dimer assay is not a high-sensitivity one?

This is a critical point. The safety of using a negative D-dimer to halt the PE workup is entirely dependent on using a modern, validated, high-sensitivity assay. If your institution uses an older, less sensitive D-dimer test, this rule-out strategy cannot be safely applied, and you should follow local protocols, which may require more frequent imaging.

Should I use an age-adjusted D-dimer cutoff?

Yes, for patients over the age of 50, using an age-adjusted D-dimer cutoff (patient’s age x 10 ng/mL, for some assays) has been shown to increase the number of patients in whom PE can be safely excluded without increasing the rate of missed diagnoses. This helps reduce unnecessary imaging in older adults, in whom D-dimer levels naturally rise.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 29, 2026