Lipid-laden macrophage index and inflammation in bronchoalveolar lavage fluids in children

The presence of lipids in alveolar macrophages has been used clinically as an indicator of aspiration, a process associated with increased lung inflammation in animal models. The hypothesis is that the quantity of lipids in alveolar macrophages, measured as lipid-laden index (LLI), would correlate with lung inflammation in paediatric patients. Children with chronic respiratory symptoms (21 cystic fibrosis (CF), 24 non-CF) underwent flexible bronchoscopy with bronchoalveolar lavage (BAL) and 24-h intraoesophageal pH monitoring for clinical indications. Total cell counts, number and per cent of neutrophils and macrophages, and LLI were determined in the bronchoalveolar lavage fluids (BALF) from all children. BALF were also obtained from eight healthy, young nonsmoking adults for comparison. LLI in non-CF children were 6.9 +/- 3.5 (mean +/- SEM) which were higher than LLI in healthy adults (1.0 +/- 0.4), (p=0.045). Children with CF had very high LLIs (19.2 +/- 4.5) compared with both healthy adults (p=0.014) and children without CF (p=0.045). LLI did not correlate with airway inflammation in any group. LLI in children with abnormal pH probes had a tendency to be higher than in children with normal pH probes, but the difference was not significant (p=0.098). It is concluded that the lipid-laden index was significantly elevated in children with chronic respiratory symptoms compared with healthy adults, and in children with cystic fibrosis compared with those who have other chronic respiratory conditions. However, the lipid-laden index did not correlate with the quantity of bronchoalveolar lavage fluid inflammation. The lipid-laden index in children may, in part, reflect processes other than aspiration, such as airways obstruction.