Feasibility of a genotyping system for the diagnosis of alpha1 antitrypsin deficiency: a multinational cross-sectional analysis

Alpha-1 Antitrypsin PI M Heterozygotes with Rare Variants: Do They Need a Clinical and Functional Follow-Up?

(1) Background: Few data are available on the risk of airway dysfunction in protease inhibitor (PI*) M heterozygotes carrying rare null or deficient allelic variants of the gene SERPINA-1 (PI*MR). (2) Methods: In this observational study, in a cohort of PI*MR heterozygotes, we evaluated respiratory functional parameters at baseline and at one-year follow-up. Moreover, we compared such parameters with those of the PI*MZ and PI*MS patients. (3) Results: A total of 60 patients were recruited; 35 PI*MR, 11 PI*MZ and 14 PI*MS. At the annual follow-up, the PI*MR and PI*MZ patients demonstrated a significantly higher FEV1 decline than the PI*MS group (p = 0.04 and p = 0.018, respectively). The PI*MR patients showed a significant increase in DLCO annual decline in comparison with the PI*MS group (p = 0.02). At baseline, the PI*MR smoking patients, compared with nonsmokers, showed statistically significant lower values of FEV1, FEV1/FVC and DLCO (p = 0.0004, p < 0.0001, p = 0.007, respectively) and, at the one-year follow-up, they displayed a significantly higher FEV1 and DLCO decline (p = 0.0022, p = 0.011, respectively). PI*MR heterozygotes with COPD showed a significantly higher FEV1, FEV1/FVC and DLCO annual decline in comparison with healthy PI*MR (p = 0.0083, p = 0.043, p = 0.041). (4) Conclusions: These results suggest that PI*MR heterozygotes, particularly smokers with COPD, have a greater annual decline in respiratory functional parameters and need to be monitored.

An Alpha-1 Antitrypsin Deficiency Screening Study in Patients with Chronic Obstructive Pulmonary Disease, Bronchiectasis, or Asthma in Turkey

Purpose

Alpha-1 antitrypsin deficiency (AATD) is a rare hereditary condition characterized by decreased serum alpha-1 antitrypsin (AAT) levels. We aim to identify AATD in patients with chronic obstructive pulmonary disease (COPD), bronchiectasis, or asthma and to report the frequency of AAT variants in Turkey.

Patients and Methods

This non-interventional, multicenter, prospective study was conducted between October 2021 and June 2022. Adult patients with COPD, bronchiectasis, asthma, liver symptoms, or family members with AATD were included. Demographic and clinical characteristics, pulmonary diagnosis, respiratory symptoms, and AAT serum levels were assessed. Whole blood samples were collected as dried blood spots, and the most common AATD mutations were simultaneously tested by allele-specific genotyping.

Results

A total of 1088 patients, mainly diagnosed with COPD (92.7%) and shortness of breath (78.7%), were assessed. Fifty-one (5%) were found to have AATD mutations. Fifteen (29.4%) patients had Pi*S or Pi*Z mutations, whereas 36 (70.6%) patients carried rare alleles Pi*M malton (n=18, 35.3% of mutations), Pi*I (n=8, 16%), Pi*P lowell (n=7, 14%), Pi*M heerlen (n=2, 4%), and Pi*S iiyama (n=1, 2%). The most common heterozygous combinations were Pi*M/Z (n=12, 24%), and Pi*M/M malton (n=11, 22%). Ten patients with severe AATD due to two deficiency alleles were identified, two with the Pi*Z/Z genotype, four with the genotype Pi*M malton/M malton, three with Pi*Z/M malton, and one with Pi*Z/M heerlen.

Conclusion

Our results identified AATD mutations as a genetic-based contributor to lung disease in patients with COPD or bronchiectasis and assessed their frequency in a population of Turkish patients.

Initial alpha-1 antitrypsin screening in Turkish patients with chronic obstructive pulmonary disease

BACKGROUND

Alpha-1 antitrypsin (AAT) deficiency is associated with several types of pathology, and the reported effects of mutations in the ATT-encoding gene vary worldwide. No Turkish study has yet appeared. We thus explored the AAT status of Turkish patients with chronic obstructive pulmonary disease (COPD).

METHODS

This prospective cross-sectional study included outpatients and inpatients treated from June 2021 to June 2022. Serum AAT levels were checked, and dry blood samples were subjected to genetic analysis.

RESULTS

: Genetic mutations were found in 21 (3.52%) of 596 patients with prior and new COPD diagnoses treated in our pneumonology outpatient department. The mean serum AAT level was 114.80 mg/dL (minimum 19, maximum 209; standard deviation 27.86 mg/dL). The most frequent mutation was M/Plowell (23.8%, n = 5), followed by M/S (23.8%, n = 5), M/I (19%, n = 4), M/Malton (14.3%, n = 3), Z/Z (9.5%, n = 2), M/Z (4.8%, n = 1), and Kayseri/Kayseri (4.8%, n = 1). Thoracic computed tomography revealed that 85.7% (n = 18) of all patients had emphysema, 28.5% (n = 6) had bronchiectasis, and 28.5% (n = 6) had mass lesions. Of the emphysema patients, 55% (n = 10) had only upper lobe emphysema, and 83.3% (n = 15) had emphysema in additional areas, but statistical significance was lacking (p > 0.05).

DISCUSSION

In patients with emphysema and normal serum AAT levels, genetic analyses may reveal relevant heterozygous mutations, which are commonly ignored. Most clinicians focus on lower lobe emphysema. Evaluations of such patients might reveal AAT mutations that are presently overlooked because they are not considered to influence COPD status.

[Results of the Implementation of a Case-Finding Program for Alpha-1 Antitrypsin Deficiency in COPD Patients]

Objectives

Currently, the identification of new cases of alpha-1 antitrypsin deficiency (AATD) continues to be one of the great challenges facing the disease. The present study aims to perform an analysis of the results of the implementation of a systematic case detection program of AATD for patients with chronic obstructive pulmonary disease.

Material and methods

Cross-sectional observational study in which the results of AAT screening until December 2022 were analyzed. The cases studied were divided into three periods: (1) no systematic case detection until 2013; (2) systematic case detection of S and Z alleles for cases with AAT < 90 mg/dL until 2018, and (3) systematic case detection of 14 mutations for cases with AAT < 120 mg/dL since 2018.

Results

A total of 471 cases were studied, of which 306 (65.0%) were carriers of some mutation related to HAD. The number of detected cases of all mutations with their percentage against those studied in each period was respectively: 6 (100%), 48 (88.8%) and 253 (61.5%). If we limit to severe mutations (AAT < 57.2 mg/dL), the distribution by periods was respectively: 3 (50.0), 10 (18.5%) and 17 (4.1%).

Conclusions

The present study describes the changes in the detection of patients carrying DAAT-related alleles with three different case identification policies. The data support the use of systematic case detection system in the COPD patient population.

Distribution of alpha1 antitrypsin rare alleles in six countries: Results from the Progenika diagnostic network

BACKGROUND

Knowledge of the frequency of rare SERPINA1 mutations could help in the management of alpha1 antitrypsin deficiency (AATD). The present study aims to assess the frequencies of rare and null alleles and their respiratory and hepatic pathogenicity.

METHODS

This is a secondary analysis of a study that evaluated the viability of the Progenika diagnostic genotyping system in six different countries by analyzing 30,827 samples from cases of suspected AATD. Allele-specific genotyping was carried out with the Progenika A1AT Genotyping Test which analyses 14 mutations in buccal swabs or dried blood spots samples. SERPINA1 gene sequencing was performed for serum AAT-genotype discrepancies or by request of the clinician. Only cases with rare mutations were included in this analysis.

RESULTS

There were 818 cases (2.6%) carrying a rare allele, excluding newly identified mutations. All were heterozygous except for 20 that were homozygous. The most frequent alleles were the M-like alleles, PI*M_malton and PI*M_heerlen. Of the 14 mutations included in the Progenika panel, there were no cases detected of PI*S_iiyama, PI*Q0_{granite falls} and PI*Q0_west. Other alleles not included in the 14-mutation panel and identified by gene sequencing included PI*M_würzburg, PI*Z_bristol, and PI*Z_wrexham, and the null alleles PI*Q0_porto, PI*Q0_madrid, PI*Q0_brescia, and PI*Q0_kayseri.

CONCLUSIONS

The Progenika diagnostic network has allowed the identification of several rare alleles, some unexpected and not included in the initial diagnostic panel. This establishes a new perspective on the distribution of these alleles in different countries. These findings may help prioritize allele selection for routine testing and highlights the need for further research into their pathogenetic role.