Rationale: The pathophysiology of acute chest syndrome (ACS) in patients with sickle cell disease is complex, and pulmonary artery thrombosis (PT) may contribute to this complication.

Objectives: To evaluate the prevalence of PT during ACS using multidetector computed tomography (MDCT).

Methods: We screened 125 consecutive patients during 144 ACS episodes. One hundred twenty-one MDCTs (in 103 consecutive patients) were included in the study.

Measurements and Main Results: Twenty MDCTs were positive for PT, determining a prevalence of 17% (95% confidence interval, 10–23%). Revised Geneva clinical probability score was similar between patients with PT and those without. D-dimer testing was very often positive (95%) during ACS. A precipitating factor for ACS was less frequently found in patients with PT as compared with those without. Patients with PT exhibited significantly higher platelet counts (517 [273–729] vs. 307 [228–412] 10⁹/L, P < 0.01) and lower bilirubin (28 [19–43] vs. 44 [31–71] μmol/L, P < 0.01) levels at the onset of ACS as compared with others. In addition, patients with PT had a higher platelet count peak (537 [345–785] vs. 417 [330–555] 10⁹/L, P = 0.048) and smaller bilirubin peak (36 [18–51] vs. 46 [32–83] μmol/L, P = 0.048) and lactate dehydrogenase peak (357 [320–704] vs. 604 [442–788] IU/L, P = 0.01) during hospital stay as compared with others.

Conclusions: PT is not a rare event in the context of ACS and seems more likely in patients with higher platelet counts and lower hemolytic rate during ACS. Patients with sickle cell disease presenting with respiratory symptoms suggestive of ACS may benefit from evaluation for PT.