Elevated bronchoalveolar lavage fluid histamine levels in allergic asthmatics are associated with increased airway obstruction

Bronchoalveolar lavage (BAL) fluid was evaluated for histamine and tryptase levels in 61 samples (46 samples from 24 atopic asthmatics, seven samples from seven patients with allergic rhinitis, and eight samples from eight normal volunteers). Asthmatics and patients with allergic rhinitis had significantly higher BAL histamine than did normal subjects (169 ± 22, 141 ± 23, 42 ± 6 pg/ml, respectively; p < 0.05, both comparisons). BAL fluid tryptase levels were also higher in asthmatics and patients with allergic rhinitis than in normal subjects (0.36 ± 0.03, 0.38 ± 0.05, 0.23 ± 0.04 ng/ml, respectively; p < 0.05, both comparisons); however, levels of tryptase and histamine in BAL were not correlated (r = -0.03 in the group as a whole, r = -0.12 in the asthmatic group). BAL concentration of histamine correlated inversely with FEV₁ percent predicted in the asthmatic group (r = -0.44, p < 0.005). Asthmatics with high BAL fluid histamine (≥ 100 pg/ml, n = 23) had lower FEV₁ percent predicted (80 ± 3% versus 96 ± 3%, p = 0.0005), lower FEV₁/FVC ratio (72 ± 1% versus 77 ± 2%, p < 0.05), higher percentage of BAL eosinophils (2.2 ± 0.4% versus 0.6 ± 0.1%, p < 0.002), and greater airway responsiveness (lower PD₂₀ [13.1 ± 3.4 versus 41.5 ± 13.7 cumulative breath units, p < 0.05]) compared with asthmatics with low BAL fluid histamine (< 100 pg/ml, n = 23). These data indicate that BAL histamine concentrations are correlated with airway obstruction in asthma and may serve as an index of severity. The lack of correlation between BAL tryptase and histamine may indicate that pulmonary basophils, rather than mast cells, could be the source for histamine in these patients.