Audit of Lysosomal Storage Diseases Testing at the National Health Laboratory Service in Johannesburg from 2011-2020
Date
2023
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Abstract
Lysosomal Storage Diseases (LSDs) are a group of Inborn Errors of Metabolism (IEM), due to the lack of a lysosomal enzyme. This results in toxic accumulation of metabolic waste products in various organs leading to neurodevelopmental regression, organ failure and premature death in the absence of treatment. Treatments for LSDs are limited. This study audited LSD diagnostic test requests received by the Division of Human Genetics, National Health Laboratory Service (NHLS) in Johannesburg from 2011 to 2020 with the aim of understanding the demand, appropriateness, and patient management of suspected LSD cases. A quantitative
survey of all samples (1861 tests) referred to NHLS Johannesburg during the study period was performed. A total of 198 (13.3%) samples were rejected for testing mainly because of faulty sample collection. Of the 1663 that were accepted for testing 1457 (87.6%) tested negative, 73 (4.4%) were inconclusive and 133 (8.0%) tested positive. Fifty-five (3.1%) patients with LSD test requests, all of which were positive, were known to a Clinical Genetics unit. The most frequently requested test was for Fabry disease: 620 (33.3% of all requests), even though this disease is not the most prevalent LSD. Of the 603 accepted test requests for Fabry disease, only 6 (1.0%) tested positive. This suggests that some referring clinicians had unrealistic expectations of encountering this disease. It should be noted, however, that testing for Fabry disease is part of a broad diagnostic workup that may be applied even if the indication for testing is not specific. Access to LSD testing was unequal: private facilities were proportionally over-represented compared to public facilities; certain provinces with large referral centres (in KZN and Gauteng) were over-represented compared to smaller centres. Feedback and education of referring clinicians regarding indications for testing and importance of patient
follow up, especially by clinical genetics services, are recommended. Follow up of positive MPS screening tests with specific diagnostic tests is essential. A system should be implemented where a medical geneticist phones the referring clinician and discusses further sample requirements (blood for enzyme analysis) and referral to a genetics clinic for all positive LSD screening tests. Future consideration should be given to designing a more systematic testing process, with the introduction of molecular testing to supplement biochemical testing.
Description
A research report submitted in partial fulfillment of the requirements for the degree of Master of Medicine to the Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, 2023
Keywords
Lysosomal Storage Diseases (LSDs), Inborn Errors of Metabolism (IEM), National Health Laboratory Service, UCTD
Citation
Novellie, Michael. (2023). Audit of Lysosomal Storage Diseases Testing at the National Health Laboratory Service in Johannesburg from 2011-2020 [Master’s dissertation, University of the Witwatersrand, Johannesburg]. WireDSpace. https://hdl.handle.net/10539/42400