SPECT Scans Show Low Risk After Negative Pulmonary Embolism Diagnosis
PATIENTS assessed with SPECT lung scans for suspected clots showed a very low risk of complications at three months, suggesting a potential role in pulmonary embolism diagnosis. Pulmonary embolism (PE) is a serious condition caused by a blood clot blocking arteries in the lungs, and rapid, accurate diagnosis is essential to prevent complications or death.
In current clinical practice, computed tomography pulmonary angiography (CTPA) is the most widely used imaging test, while traditional ventilation-perfusion (V/Q) scans are also used in selected cases. A newer approach, single photon emission computed tomography (SPECT) V/Q scanning, has been increasingly adopted, although it is not yet fully endorsed by clinical guidelines due to limited trial evidence.
Trial Compares Three Imaging Strategies
In a multicentre randomised trial involving 603 patients with suspected PE, researchers compared three diagnostic strategies: SPECT V/Q scanning, CTPA, and planar V/Q scanning. The study aimed to determine whether SPECT V/Q could match established methods in safely ruling out PE.
Pulmonary embolism was diagnosed at similar rates across groups, affecting around one in five patients in both the SPECT and CTPA arms, and slightly fewer in the planar V/Q group.
Low Three-Month Clot Risk Across All Methods
Among patients who were not treated after a negative test result, the risk of developing venous thromboembolism (VTE) within three months was low across all strategies. Rates were 0.5% for SPECT V/Q, 0% for CTPA, and 0.8% for planar V/Q.
Although the study did not formally demonstrate that SPECT V/Q was non-inferior to standard approaches, the similarly low event rates suggest that it may still be a clinically safe option in selected patients.
Implications for Clinical Practice
For clinicians, these findings indicate that SPECT V/Q could serve as a viable alternative imaging strategy, particularly in patients where CTPA is less suitable, such as those with contrast allergies or concerns about radiation exposure.
However, the trial was stopped early due to recruitment and funding challenges, limiting its statistical power. As a result, further research is needed before SPECT V/Q can be fully integrated into guideline-recommended pathways.
Overall, the study adds to growing evidence that alternative imaging strategies may support safe and effective pulmonary embolism diagnosis, while offering flexibility in clinical decision-making.
Reference
Le Pennec R et al. Comparison of Three Diagnostic Strategies for Suspicion of Pulmonary Embolism: Planar Ventilation-Perfusion Scan (V/Q), Computed Tomography Pulmonary Angiography (CTPA), and Single Photon Emission Computed Tomography Ventilation-Perfusion Scan (SPECT V/Q): a multicenter, non-inferiority randomised controlled trial. Eur Respir J. 2026; DOI: 10.1183/13993003.01742-2025.
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