Cutoff value of lipid-laden alveolar macrophages for diagnosing aspiration in infants and children

Abstract

Chronic passage of gastric and/or alimentary material into the airways is a frequent and difficult-to-diagnose condition. Because alveolar macrophages phagocytose aspirated material, it has been suggested that their identification is a useful diagnostic method. To know the usefulness of the lipid-laden alveolar macrophages (LLAM) index as a diagnostic tool for aspiration, children from 1 month to 16 years of age were included in three groups: G-I, children with pulmonary pathology and suspicion of aspiration by clinic or image evaluation; G-II, with pulmonary pathology without suspicion of aspiration; and G-III, without respiratory symptoms nor suspicion of aspiration. Bronchoalveolar lavage was obtained through bronchoscopy in G-I and G-II, and through endotracheal tube in G-III, and the LLAM index (0-400) was determined. A total of 112 patients (41, 30, and 41 in G-I to III, respectively) were studied. LLAM index (mean +/- SEM) was highest in G-I (233.2 +/- 5.5), as compared with G-II (187.8 +/- 11.6, P < 0.05), and G-III (108.5 +/- 13.5, P < 0.001). However, notable overlap of LLAM values was observed between G-I and G-II, and between G-II and G-III. When patients from G-I and G-III were jointly analyzed, the area under the ROC curve for diagnosing aspiration was 0.92, with a best cutoff value of >165 (98.6% sensitivity, 78.0% specificity, 87.8% overall accuracy). LLAM index, with a cutoff value of >165 is a useful diagnostic test for aspiration when there is suspicion of this condition. However, due to its low specificity, it does not discriminate other causes of chronic lung disease.