By David Jolley
Our Friday seminar drew us to be aware of a short article in this month’s issue of Age and Ageing from Cochrane Foundation, with the intriguing title: When is Alzheimer’s not dementia? https://academic.oup.com/ageing/article/48/2/174/5133577
The authors had published in January an article making similar points in ‘Alzheimer’s and Dementia’ https://alzheimersanddementiajournal.com/article/S1552-5260(18)33581-7/fulltext
They are writing about guidance on the diagnosis of Alzheimer’s disease by the National Institute on Ageing and the Alzheimer’s Association (NIA-AA) issued in 2018 and published in ‘Alzheimer’s and dementia’ https://www.ncbi.nlm.nih.gov/pubmed/29653606 . This new guidance moves matters on from guidance of 2012 which recommended the use of biological markers as adjuncts to clinical characterisation of Alzheimer’s disease, to make the presence of biological markers diagnostic in the absence of clinical symptoms. The markers identify amyloid deposits, fibrillary tau and neurodegeneration. They are demonstrated by examination of the Cerebrospinal Fluid and neuroimaging.
The conservative and highly regarded Cochrane commentators point out that the relationship between the clinical condition, which is what patients, family carers and their professional carers and physicians are concerned with, and these biomarkers is far from equivalence: some people who have clear evidence of the clinical condition do not have the biomarkers. Most importantly in this context, people with the biomarkers do not have clinical impairment and often never develop it.
While the use of biomarkers to define groups for research purposes is reasonable, the extension of their application to clinical practice is unjustified and potentially harmful. ‘Clinical creep’ is the powerful warning term the authors use to describe the inclusion of thousands of normal older people into the diagnosis of Alzheimer’s as required by the new NIA-AA guidelines. This might suit some commercial organisations and even charities, but it would misdirect huge amounts of funds and other resources and raise unsubstantiated worries amongst individuals, families and the caring public. In most economies, the application will be unthinkable – unaffordable.
The enthusiasm of the NIA-AA authors is understandable but it would be inexcusable to adopt their criteria into clinical practice for this would surely do more harm than good. Let us hope that the wise words of the Cochrane Group can hold the day.