Milk protein and Oil-Red-O staining of alveolar macrophages in chronic respiratory disease of infancy

Aspiration is a suspected cause of chronic respiratory disease in infants. We assessed the probability of aspiration by immunocytochemical staining of alveolar macrophages for milk proteins (α-lactalbumin and β-lactoglobulin) and compared these findings with the Oil-Red-O staining score. Broncho-alveolar lavage (BAL), 24-hr esophageal pH-measurement and/or gastro-esophageal scintigraphy were performed in 111 children. Seventy-nine patients were enrolled. Ten exclusively soya milk formula fed children served as a control group. Individual scores, expressed as the mean percentage of positive staining macrophages counted by three blinded authors were made. Relying on the control group, a positive score was defined as a value higher than 1%. A positive score was found in 26% (18/69). Forty-four percent (8/18) of them had positive gastro-esophageal reflux (GER) tests. In 61% (11/18) a concomitant diagnosis of laryngo-/tracheomalacia was made. A positive score was found in 48% (11/23) of patients with laryngo-/tracheomalacia, compared to 15% (7/46) in infants with normal laryngeal and tracheal anatomy. No correlation was found between the immunocytochemical staining score for milk proteins and the Oil-Red-O staining score. We conclude that assuming the 1% criterion, persistent respiratory symptoms were associated with a positive immunostaining score, suggestive for aspiration, in 26% of infants, in 48% in case of concomitant laryngo- and/or tracheomalacia and in 15% of infants with normal laryngeal and tracheal anatomy. No correlation was found between the immunocytochemical staining score for cow milk proteins and the Oil-Red-O staining score.