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Research paper
Usefulness of frataxin immunoassays for the diagnosis of Friedreich ataxia
  1. Eric C Deutsch1,2,3,
  2. Devin Oglesbee4,
  3. Nathaniel R Greeley2,
  4. David R Lynch1,2,3
  1. 1Department of Pharmacology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
  2. 2Department of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
  3. 3Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
  4. 4Department of Laboratory Medicine and Pathology, Department of Molecular Genetics, Mayo Clinic School of Medicine, Mayo Clinic, Rochester, Minnesota, USA
  1. Correspondence to Dr David R Lynch, Division of Neurology, The Children's Hospital of Pennsylvania, 502 Abramson Research Center, Philadelphia, PA 19104; lynchd{at}mail.med.upenn.edu

Abstract

Background Friedreich ataxia (FRDA) is a neurodegenerative disease caused by mutations in the frataxin (FXN) gene, resulting in reduced expression of the mitochondrial protein frataxin. Improved understanding of the pathophysiology of the disease has led to a growing need for informative biomarkers to assess disease progression and response to therapeutic intervention.

Objective To evaluate the performance of frataxin measurements as a diagnostic tool using two different immunoassays.

Methods Clinical and demographic information was provided through an ongoing longitudinal natural history study on FRDA. Frataxin protein levels from multiple cell types in controls, carriers and FRDA patients were measured and compared using a lateral flow immunoassay and a Luminex xMAP-based immunoassay. Receiver operating characteristic curve analyses were then performed to evaluate the sensitivity, specificity, and positive and negative predictive values for each immunoassay.

Results For whole blood and buccal cells, analysing FRDA patients and carriers together in a cohort resulted in higher sensitivities and positive predictive values compared with analyzing controls and carriers together, with similar results between each tissue type. We then compared the usefulness of a lateral flow immunoassay with a multianalyte Luminex xMAP-based immunoassay, and showed that both assays demonstrate high positive predictive values with low rates of false negatives and false positives.

Conclusions Frataxin measurements from peripheral tissues can be used to identify FRDA patients and carriers. While multiple cell types and assays may be useful for diagnostic purposes, each assay and cell type used has its advantages and disadvantages depending on study design and scope.

  • MITOCHONDRIAL DISORDERS
  • MOVEMENT DISORDERS
  • PAEDIATRIC

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