Induced sputum versus bronchoalveolar lavage during acute chest syndrome in sickle cell disease

Previous reports have shown that in more than 40% of adults with acute chest syndrome (ACS), fat droplets suggestive of pulmonary fat embolism were present in alveolar macrophages. To determine whether induced sputum (IS) is a reliable test for detecting this embolism, we compared bronchoalveolar lavage and IS results in 20 patients with ACS. We found a correlation between the number of Oil Red O-stained macrophages in sputum and lavage fluid (Spearman's coefficient: rho = 0.657, p < 0.018). Sputum cytology was then studied in another 60 patients who had sickle cell disease with ACS. An elevated percentage of Oil Red O-stained macrophages was found in the sputum of 37/47 patients, but they did not include any of the patients with sickle cell disease but no clinical symptoms. Patients suffering from ACS with Oil Red O-stained macrophages had more extrathoracic concomitant pain than those without (76 vs. 50%, p < 10-8), had more neurologic symptoms (7 vs. 0%, p < 10-8), a lower differential platelet count (-49 +/- 121 vs. +85 +/- 229, p < 0.04), and higher abnormal transaminase values (28 vs. 17%, p < 0.01). We conclude that IS analysis is a safe, noninvasive, and useful test for fat embolism detection in ACS.