Longitudinal evaluation of individuals with severe alpha-1 antitrypsin deficiency (Pi*ZZ genotype)

Background and aims

Homozygous Pi*Z mutation in alpha-1 antitrypsin (Pi*ZZ genotype) predisposes to pulmonary loss-of-function and hepatic gain-of-function injury. To facilitate selection into clinical trials typically targeting only one organ, we systematically evaluated an international, multicenter, longitudinal, Pi*ZZ cohort to uncover natural disease course and surrogates for future liver- and lung-related endpoints.

Methods

Cohort 1 recruited 737 Pi*ZZ individuals from 25 different centers without known liver comorbidities that received a baseline clinical and laboratory assessment as well as liver stiffness measurement (LSM). A follow-up interview was performed after at least six months. Cohort 2 consisted of 135 Pi*ZZ subjects without significant liver fibrosis, who received a standardized baseline and follow-up examination at least two years later, both including LSM.

Results

During 2634 patient-years of follow-up, 39 individuals died, with liver and lung being responsible for 46% and 36% of deaths, respectively. 41 Pi*ZZ subjects who developed a hepatic endpoint presented with significantly higher baseline liver fibrosis surrogates, i.e., LSM (24 vs. 5 kPa, p<.001) and AST-to-platelet ratio index (APRI, 1.1 vs. 0.3 units, p<.001). Liver-related endpoints within five years were most accurately predicted by LSM (area under the curve [AUC] 0.95) followed by APRI (0.92). Baseline lung parameters displayed only a moderate predictive utility for lung-related endpoints within five years (FEV1 AUC 0.76). Fibrosis progression in those with no/mild fibrosis at baseline was rare and primarily seen in those with preexisting risk factors.

Conclusions

Non-invasive liver fibrosis surrogates accurately stratify liver-related risks in Pi*ZZ individuals. Our findings have direct implications for routine care and future clinical trials of Pi*ZZ patients.