SERPINA1 and alpha 1-antitrypsin deficiency: However, the peptides C37 [rs = −0.74; 95% CI (−0.93, −0.34)] and C42 [rs = −0.79; 95% CI (−0.92, −0.43)] were negatively associated with age, suggesting that their levels decrease independently from the total AAT level as children with AATD grow older.