Imaging for Pulmonary Embolism in Sickle Cell Disease: A 17-Year Experience

Sickle cell disease, a complex disorder with known pulmonary complications, has the potential to confound the diagnosis of pulmonary embolism. We hypothesized that when the choice of imaging is guided by chest radiographic results, CT pulmonary angiography (CTPA) and ventilation-perfusion (V/Q) scintigraphy have comparable diagnostic performance in sickle cell disease. Methods: A retrospective cohort of adults with sickle cell disease who were imaged for suspected pulmonary embolism with either CTPA or V/Q, from 2000 to 2016 at our institution, was established. To reduce radiation exposure, our practice recommends V/Q for stable patients with normal chest radiographs. Results of index pulmonary embolism imaging, 90-d follow-up, and results of chest radiography were recorded. Results: Two hundred forty-five adults with sickle cell disease comprised the cohort. The mean age (±SD) was 33 ± 10.5 y, and 58% (141) were men. Index imaging was V/Q in 62.9% (n = 154) and CTPA in 37.1% (n = 91). Chest radiographs, performed in 96.3% (n = 236), were normal in 72.9% (n = 172). Imaging results for pulmonary embolism were negative in 88.2% (n = 216), positive in 4.1% (n = 10), and indeterminate in 7.8% (n = 19) with no difference between V/Q and CTPA (P = 0.63). Reimaging within 90 d occurred in 9.8% (n = 24), 14.7% (20/136) after initial V/Q, and 5% (4/109) after initial CTPA (P = 0.08). Reimaging revealed a pulmonary embolism diagnosis after negative/indeterminate results in 0.7% (1/149) of V/Qs and 1.2% of (1/86) CTPAs (P = 0.69). Over the 17-y study period, 47% (114/245) underwent repeated imaging, and 11% (27/245) were diagnosed with pulmonary embolism at least once. Conclusion: In sickle cell disease patients with suspected pulmonary embolism, positive imaging rates were low for any given clinical presentation, but 11% of the cohort was diagnosed with pulmonary embolism over the 17-y study period. CTPA and V/Q performed comparably for pulmonary embolism diagnosis when the choice of imaging was guided by results of chest radiography. Hence, V/Q is a reasonable first choice for sickle cell disease patients with normal chest radiographs.