The diagnosis of Huntington’s disease by different molecular tools: a systematic review

Huntington's disease (HD) is a neurodegenerative condition resulting from CAG trinucleotide expansion in the HTT. We reviewed various molecular tools for diagnosing HD and their respective validations and outlined their advantages and disadvantages. We utilized PubMed, employing Huntington's disease OR chorea AND Molecular Diagnosis OR Molecular Diagnostic Techniques as keywords. This review was submitted to the PROSPERO platform (nºCRD42021253951). The PRISMA checklist was used, and bias assessment followed the guidelines outlined in the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy. 845 articles were retrieved, 17 were selected for full-text review, and two additional articles were manually included, resulting in 19 that presented the validation method: only three studies reported the limits of detection, reproducibility, sensitivity, and specificity, which are essential for validating these techniques, given the unstable nature of CAG regions; six calculated at least one of these parameters, and 10 did none. We identified significant variability in the validation methods with only three thoroughly assessing the key validation parameters. The lack of standardized validation approaches may compromise diagnostic accuracy, impacting genetic counseling and clinical management. TPPCR coupled with capillary electrophoresis, demonstrated high accuracy, whereas gel electrophoresis-based methods exhibited lower sensitivity and specificity.