Chronic obstructive pulmonary disease with intermediate alpha-1-antitrypsin deficiency

Chronic obstructive pulmonary disease in alpha1-antitrypsin PI MZ heterozygotes: a meta-analysis

BACKGROUND

Severe alpha(1)-antitrypsin deficiency, usually related to homozygosity for the protease inhibitor (PI) Z allele, is a proven genetic risk factor for chronic obstructive pulmonary disease (COPD). The risk of COPD in PI MZ heterozygous individuals is controversial.

METHODS

A search of MEDLINE from January 1966 to May 2003 identified studies that examined the risk of COPD in PI MZ individuals and studies that measured forced expiratory volume in 1 second (FEV(1)) in heterozygotes.

RESULTS

In 16 studies that reported COPD as a categorical outcome, the combined odds ratio (OR) for PI MZ versus PI MM (normal genotype) was 2.31 (95% CI 1.60 to 3.35). The summary OR was higher in case-control studies (OR 2.97; 95% CI 2.08 to 4.26) than in cross sectional studies (OR 1.50; 95% CI 0.97 to 2.31) and was attenuated in studies that adjusted for cigarette smoking (OR 1.61; 95% CI 0.92 to 2.81). In seven studies that reported FEV(1) as a continuous outcome there was no difference in mean FEV(1) between PI MM and PI MZ individuals.

CONCLUSIONS

Case-control studies showed increased odds of COPD in PI MZ individuals, but this finding was not confirmed in cross sectional studies. Variability in study design and quality limits the interpretation. These results are consistent with a small increase in risk of COPD in all PI MZ individuals or a larger risk in a subset. Future studies that adjust for smoking and include other COPD related phenotypes are required to conclusively determine the risk of COPD in PI MZ heterozygotes.

Influence of cadmium and other trace metals on human alpha1-antitrypsin: an in vitro study

The effect of trace metals on plasma alpha1-antitrypsin was studied in vitro by adding known concentrations of trace metals, either alone or in combination, to plasma. Cadmium was the only trace metal that reduced the concentration of alpha1-antitrypsin and depressed the trypsin inhibitory capacity. No such effects were found with divalent lead, mercury, nickel, iron, and zinc ions. The present study appears to offer a plausible explanation for the emphysema that occurs in industrial workers exposed to cadmium.