Clinical Opal - Gene Testing
On further questioning, Belinda tells you that she has recently seen a naturopath for generalised fatigue and weight gain. The naturopath has advised that she see you for MTHFR gene testing to allow a ‘more targeted approach to vitamin supplementation’.
Belinda is otherwise well and denies any other significant PMH. She takes no regular medications.
What do you advise regarding Belinda’s request for genetic testing?
The MTHFR gene is responsible for the production of the enzyme methylenetetrahydrofolate reductase (MTHFR), fundamental to metabolism of folate.
Genetic testing for two polymorphisms in the MTHFR gene, 677C>T and 1298A>C, is increasingly being requested by GPs and other practitioners. These polymorphisms are common, affecting up to 65% of the population. They have been weakly associated with multiple conditions, including autism, mental illness, cardiac disease, neural tube defects, infertility, poor pregnancy outcomes and colorectal cancer.1
However, both the RACGP Genomics in General Practice guidelines and the newly published RACGP First Do No Harm guidelines state that there is no significant evidence of a causal link between MTHFR gene variations and particular diseases, and that there is ‘no evidence-based treatment that will improve health outcomes for a patient who has one or both MTHFR gene variants’. Consequently, they recommend avoiding requesting a MTHFR gene test as there is ‘no substantial evidence to support the use of MTHFR gene testing in routine clinical practice’.
This is consistent with the recommendations of the Choosing Wisely Australia initiative: don’t undertake genetic testing for methylenetetrahydrofolate reductase (MTHFR) where the clinical utility for diagnostic purposes is extremely low.
For more guidance on pathology tests, check out 'Testing, testing, 1,2,3', a new, free online educational program designed to support GPs to use pathology tests more effectively and reduce the harms of non-rational testing. 'Testing, testing, 1, 2, 3' comprises a series of interactive reflective activities, eLearning cases, quizzes and scenarios. Developed by GPs, it will give you evidence-based information and practical strategies to support more rational testing in your day to day practice. Click here to see more.
References:
Simon is a GP based in Newcastle, NSW, and a senior medical educator with Medcast. He also has medical education roles with the RACGP and GPSA.
Over the past three decades, Simon has worked in clinical and educational roles in NSW and the NT, as well as in the Republic of Ireland. He has published over 75 peer reviewed journal articles, and in 2018 received the RACGP Corliss award for his contribution to medical education.
Simon is passionate about high quality education and training. He has particular interests in GP supervisor professional development and the rational use of tests and medicines. He is a proud member of Doctors for the Environment. He spends his spare time drinking craft beer and pretending that he is a musician in the Euthymics, an all-GP band.
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