Serum alpha 1-antitrypsin levels in asthmatic children

Serum levels of alpha 1-antitrypsin (AAT) were determined by an enzymatic assay method in fifty-five asthmatic children and in the same number of controls. The mean AAT level was significantly lower in asthmatics (1.65 mumol/min/ml) than in controls (2.0 mumol/min/ml) (P less than 0.02). A significantly higher proportion of asthmatics than controls (P less than 0.05) had levels below 2.1 mumol/min/ml which is the lower limit of normal, thus suggesting a higher prevalence of partial (heterozygous) AAT deficiency in the asthmatics. There was no relationship between the mean AAT levels and age, duration of asthma or frequency of asthmatic attacks. Although there is some controversy about the relationship between heterozygous AAT deficiency and pulmonary disease, severe (homozygous) AAT deficiency has been linked with emphysema which is also a complication of asthma. There was however, no evidence of emphysema in either the asthmatic child or the control who had no detectable serum AAT. There were three asthmatics whose chest radiographs showed hyperinflation, but had a mean AAT level that was not significantly different from that in those without such changes. Further studies, including phenotype determination in a larger group of asthmatic children, are required in order to determine the prevalence of both homozygous and heterozygous AAT deficiencies which may be risk factors in the development of emphysema and other pulmonary complications of asthma.