Histamine Sensitivity Does Not Separate Asthma From Chronic Bronchitis

Airway hyperreactivity was assessed by graded histamine aerosol (0.03 to 25mg/ml) in 15 normal, 52 asthmatics and 107 chronic bronchitics. The mean PC20 was 8.2±1.53, 0.4 ±0.54 and 0.6 ±0.85 mg/ml. in the respective groups. While there was a significant tendency for those with lower FEV1 to show hyper-reactivity; this was more evident in bronchitis (p<0.05). There was very significant relationship between index of obstruction (FEV1/FVC%) and greater hyperreactivity, again more closely in bronchitics. While there were no differences as a group for reactivity between two patient groups, in bronchitics greater obstruction or lower FEV1 seem to account for a higher reactivity. There was no relation to degree of bronchoreversibility in both but asthmatics showed much greater prevalence of cutaneous atopy.