Alpha-1 antitrypsin Pi*SS genotype and risk of pulmonary disease. An EARCO Research project

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Pi*S is one of the most common deficient variants of alpha-1 antitrypsin. However, the potential risk for pulmonary disease remains unclear for the Pi*SS genotype. We analysed the Pi*SS population in EARCO and compared it with Pi*ZZ and Pi*SZ subjects to determine the potential risk for lung disease in Pi*SS individuals using a propensity score matching adjusted for age, sex and smoking. Results: Among 1453 individuals, we identified 56 (3.85%) Pi*SS, 58.9% men, mean age 59 y.o. 67.9% ex-smokers, with a mean of 34.8 pack-years. In 71.4% there was pulmonary disease: COPD (41.1%), emphysema (23.2%), asthma (19.6%), and bronchiectasis (17.9%). On average, they had a mild obstructive pattern (FEV1 84.4%; FEV1/FVC 0.67), with mild DLCO impairment (DLCO 77.8%), and were infrequent exacerbators (0.52 exacerbations/last year). In the matched population, lung disease (p=0.017), including COPD (p=0.014) and emphysema (p<0.001) were more frequent for Pi*ZZ compared to Pi*SS. Mean FEV1 (61.34 vs 83.4%; p<0.001) and KCO (68.65 vs 81.08%; p=0.002) were significantly lower for Pi*ZZ than for Pi*SS, respectively. No significant differences were found in prevalence of asthma or bronchiectasis. Matched to Pi*SZ, Pi*SS subjects had a greater tendency for asthma (19.6% vs 8.9%; p=0.10), without significant differences in lung disease or function. Conclusion: The number of Pi*SS individuals registered in EARCO is lower than expected. The risk of lung disease associated with the Pi*SS genotype is significantly lower than with Pi*ZZ but not different from Pi*SZ, except for a trend towards more frequent asthma. Larger series of Pi*SS must be analyzed to clearly establish the risk of asthma associated with this genotype.

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