Molecular testing for hereditary hemochromatosis

National trends and outcomes of genetically inherited non-alcoholic chronic liver disease in the USA: estimates from the National Inpatient Sample (NIS) database

Background

Medical literature on the prevalence of genetic liver disease is lacking. In this study, we investigated the in-hospital healthcare and economic burden from genetic causes of non-alcoholic chronic liver disease (NACLD) and non-alcoholic liver cirrhosis (NALC) in the USA.

Methods

Data were abstracted from the National Inpatient Sample database between 2002 and 2014 using ICD9 codes for patients discharged with NACLD and NALC secondary to genetic diseases including alpha-1 antitrypsin deficiency (A1ATd), cystic fibrosis (CF), Wilson disease (WD), hereditary hemochromatosis (HHC), glycogen storage disease, and disorders of aromatic amino-acid metabolism (DAAAM).

Results

Throughout the study period, there were 19,332 discharges for NACLD associated with the six genetic diseases including 14,368 for NALC. There were $1.09 billion in hospital charges, 790 in-hospital deaths, and 955 liver transplants performed. Overall, A1ATd was associated with 8,983 (62.52%) hospitalizations for NALC followed by WD, CF, and HHC. The highest in-hospital mortality was seen with HHC. The greatest frequency of liver transplants was seen with DAAAM.

Conclusion

The number of hospitalizations for genetic liver diseases continues to increase. With increased funding and directed research efforts, we can aim to improve medical treatments and the quality of life for patients at risk for liver deterioration.

Validation of the Hemochromatosis (2SNP+) Direct EUROArray Assay for the Molecular Diagnosis of HFE-Related Hereditary Hemochromatosis

Aim: Two missense variants in the HFE gene, c.845G>A (p.Cys282Tyr) and c.187C>G (p.His63Asp), are commonly screened as part of the diagnostic workup for HFE-related hereditary hemochromatosis (HH) and iron overload. Identification of the two variants can be achieved by polymerase chain reaction (PCR)-based laboratory tests and other methods. Evaluation of the analytical performance of the test is essential to ensure that the assay is precise and accurate. The aim of this study was to evaluate the analytical performance of the DNA microarray-based Hemochromatosis (2SNP+) Direct assay on the EUROArray test system (EUROIMMUN, Lübeck, Germany). Materials and Methods: Evaluation of the commercial assay was performed on 50 clinical blood samples and 26 retrospective College of American Pathologists (CAP)-provided external quality assurance (EQA) DNA samples and compared to a laboratory-developed PCR-restriction enzyme digestion (PCR-RE) test and DNA sequencing. Results and Discussion: HFE genotyping results obtained from both Hemochromatosis (2SNP+) Direct and PCR-RE assays were 100% concordant with nucleotide sequencing for all clinical samples evaluated. One hundred percent accuracy was also achieved on the retrospective CAP EQA samples. Precision studies performed on wild type and c.845G>A/c.187C>G compound heterozygous whole blood samples showed 100% intra-run repeatability (N = 3) and 100% inter-run reproducibility (N = 3), respectively. Conclusion: The Hemochromatosis (2SNP+) Direct EUROArray test provides a rapid and accurate method of detection for both the c.845G>A and c.187C>G variants for molecular diagnosis of HFE-related HH.

Genotyping single nucleotide polymorphisms by MALDI mass spectrometry in clinical applications

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry has become one of the most powerful and widely applied technologies for SNP scoring and determination of allele frequencies in the post-genome sequencing era. Although different strategies for allele discrimination combined with MALDI were devised, in practice only primer extension methods are nowadays routinely used. This combination enables the rapid, quantitative, and direct detection of several genetic markers simultaneously in a broad variety of biological samples. In the field of molecular diagnostics, MALDI has been applied to the discovery of genetic markers, that are associated with a phenotype like a disease susceptibility or drug response, as well as an alternative means for diagnostic testing of a range of diseases for which the responsible mutations are already known. It is one of the first techniques with which whole genome scans based on single nucleotide polymorphisms were carried out. It is equally well suited for pathogen identification and the detection of emerging mutant strains as well as for the characterization of the genetic identity and quantitative trait loci mapping in farm animals. MALDI can also be used as a detection platform for a range of novel applications that are more demanding than standard SNP genotyping such as mutation/polymorphism discovery, molecular haplotyping, analysis of DNA methylation, and expression profiling. This review gives an introduction to the application of mass spectrometry for DNA analysis, and provides an overview of most studies using SNPs as genetic markers and MALDI mass spectrometric detection that are related to clinical applications and molecular diagnostics. Further, it aims to show specialized applications that might lead to diagnostic applications in the future. It does not speculate on whether this methodology will ever reach the diagnostic market.