Clinical drivers of hospitalisation in patients with mitochondrial diseases

Background

Mitochondrial diseases in adults are generally chronic conditions with a wide spectrum of severity contributing to disease burden and healthcare resource utilisation. Data on healthcare resource utilisation in mitochondrial diseases are limited.

Objectives

We performed a retrospective longitudinal study to investigate the clinical drivers of hospitalisation in adult patients with mitochondrial diseases to better understand healthcare resource utilisation.

Methods

We recruited participants from our specialised Mitochondrial Disease Clinic in Sydney, Australia between September 2018 and December 2021. We performed a retrospective chart review for the period 2013-2022 considering emergency department (ED) and/or hospital admission notes, as well as discharge summaries. We used multiple linear regression models to examine the association between the type of presenting symptom(s) and duration of hospital stay and frequency of admissions, while adjusting for relevant covariates.

Results

Of the 99 patients considered, the duration of hospitalisation ranged from 0 to 116 days per participant and the number of admissions ranged from 0 to 21 per participant. Participants with one or more mitochondrial disease-associated admissions constituted 52% of the study cohort. 13% of the participants presented to the ED without requiring an admission and 35% never attended the ED or required a hospital admission during this period. Neurological (p<0.0001), gastroenterological (p=0.01) and symptoms categorised as 'other' (p<0.0001) were the main presentations driving the total number of days admitted to hospital. A statistically significant association was evident for the number of admissions and all types of presenting symptoms (p<0.0001).

Conclusion

There are variable reasons for hospitalisation in adults with mitochondrial diseases, with neurological and gastroenterological presentations being associated with prolonged and complex hospitalisation. A better understanding of clinical drivers such as these allows for better informed and well-coordinated management aimed at optimising healthcare resource utilisation.

Use of Whole-Genome Sequencing for Mitochondrial Disease Diagnosis

BACKGROUND AND OBJECTIVES

Mitochondrial diseases (MDs) are the commonest group of heritable metabolic disorders. Phenotypic diversity can make molecular diagnosis challenging, and causative genetic variants may reside in either mitochondrial or nuclear DNA. A single comprehensive genetic diagnostic test would be highly useful and transform the field. We applied whole-genome sequencing (WGS) to evaluate the variant detection rate and diagnostic capacity of this technology with a view to simplifying and improving the MD diagnostic pathway.

METHODS

Adult patients presenting to a specialist MD clinic in Sydney, Australia, were recruited to the study if they satisfied clinical MD (Nijmegen) criteria. WGS was performed on blood DNA, followed by clinical genetic analysis for known pathogenic MD-associated variants and MD mimics.

RESULTS

Of the 242 consecutive patients recruited, 62 participants had "definite," 108 had "probable," and 72 had "possible" MD classification by the Nijmegen criteria. Disease-causing variants were identified for 130 participants, regardless of the location of the causative genetic variants, giving an overall diagnostic rate of 53.7% (130 of 242). Identification of causative genetic variants informed precise treatment, restored reproductive confidence, and optimized clinical management of MD.

DISCUSSION

Comprehensive bigenomic sequencing accurately detects causative genetic variants in affected MD patients, simplifying diagnosis, enabling early treatment, and informing the risk of genetic transmission.

Patient Care Standards for Primary Mitochondrial Disease in Australia. An Australian adaptation of the Mitochondrial Medicine Society recommendations

This document provides consensus‐based recommendations for general physicians and primary care physicians who diagnose and manage patients with mitochondrial diseases (MD). It builds on previous international guidelines, with particular emphasis on clinical management in the Australian setting. This statement was prepared by a working group of medical practitioners, nurses and allied health professionals with clinical expertise and experience in managing Australian patients with MD. As new treatments and management plans emerge, these consensus‐based recommendations will continue to evolve, but current standards of care are summarised in this document.

Confirmed versus suspected: The social significance of a genetic or non-genetic diagnosis of mitochondrial disease

This study assessed attitudes and beliefs regarding the importance of a genetic versus non-genetic diagnosis within the mitochondrial disease community. Survey respondents were categorized into two groups - those with a genetic diagnosis, and those with a non-genetic diagnosis of mitochondrial disease. We found that while both groups perceive problems with the support available to adult mitochondrial disease patients, the non-genetic group experiences less medical and social support due to lack of a definitive diagnosis. Understanding the efficacy of existing resources for mitochondrial disease sub-groups will allow for the development or improvement of resources designed to meet patient needs.

The broadening spectrum of mitochondrial disease: shifts in the diagnostic paradigm

BACKGROUND

The diagnosis of mitochondrial disease requires a complex synthesis of clinical, biochemical, histological, and genetic investigations. An expanding number of mitochondrial diseases are being recognized, despite their phenotypic diversity, largely due to improvements in methods to detect mutations in affected individuals and the discovery of genes contributing to mitochondrial function. Improved understanding of the investigational pitfalls and the development of new laboratory methodologies that lead to a molecular diagnosis have necessitated the field to rapidly adopt changes to its diagnostic approach.

SCOPE OF REVIEW

We review the clinical, investigational and genetic challenges that have resulted in shifts to the way we define and diagnose mitochondrial disease. Incorporation of changes, including the use of fibroblast growth factor 21 (FGF-21) and next generation sequencing techniques, may allow affected patients access to earlier molecular diagnosis and management.

MAJOR CONCLUSIONS

There have been important shifts in the diagnostic paradigm for mitochondrial disease. Diagnosis of mitochondrial disease is no longer reliant on muscle biopsy alone, but should include clinical assessment accompanied by the use of serological biomarkers and genetic analysis. Because affected patients will be defined on a molecular basis, oligosymptomatic mutation carriers should be included in the spectrum of mitochondrial disease. Use of new techniques such as the measurement of serum FGF-21 levels and next-generation-sequencing protocols should simplify the diagnosis of mitochondrial disease.

GENERAL SIGNIFICANCE

Improvements in the diagnostic pathway for mitochondrial disease will result in earlier, cheaper and more accurate methods to identify patients with mitochondrial disease. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.