With a new definition, Alzheimer’s disease could be detected sooner, which would have many advantages, one of which would be the possibility of selecting patients for clinical trials of disease-modifying medications aimed at early stages of the disease. The new definition includes recent breakthroughs in Alzheimer’s research, for example, the detection of biomarkers which are fundamental to diagnosis. The new lexicon has been put forward by experts from around the world, according to a Position Paper published in the November issue of The Lancet Neurology.
Basing its criteria on biological features and patterns of cognitive changes, the International Working Group for New Research and Criteria for the Diagnosis of Alzheimer’s Disease (AD) put forward a new diagnostic framework aimed at better, earlier and more accurate diagnosis of AD in 2007
The same international working group, led by Bruno Dubois, Salpêtrière Hospital, Paris, France, has redefined AD as a clinical-biological syndrome allowing for prompter diagnosis, rather than having to wait for a post-mortem examination to certify the presence of the disease. A diagnosis can be confirmed on living patients on the basis of easily identifiable biomarkers which can be spotted early on during the disease.
The authors explain that when diagnosing Alzheimer’s disease the clinician no longer has to wait for the presence of full-blown dementia. Nowadays, with the presence of at least one positive biomarker that shows up on MRI (magnetic resonance imaging), PET neuroimaging or CSF (cerebrospinal fluid), plus episodic memory impairment, the criteria for AD diagnosis may be met. This new approach to AD diagnosis means patients can be identified earlier and accurately, before clinical symptoms appear.
The authors write:
..that there is no longer a reason to wait until patients have developed full-blown dementia or to exclude from diagnosis and treatment a large number of patients who lack functional disability yet express the disease.
The value of these definitions is their potential application in clinical trials of disease-modifying drugs. Individuals identified as ‘asymptomatic at risk for AD’ or ‘presymptomatic AD’ might be enrolled in trials aimed at delaying onset of clinical signs. Patients with prodromal AD [predementia stage of AD] could be included in trials of drugs targeting progression to more severe stages of AD. Uniformity of definitions will assist in constructing trial populations and comparing results across trials.
Lon Schneider from the University of Southern California Keck School of Medicine and the University of Southern California Alzheimer’s Disease Research Center in Los Angeles, writes in an Accompanying Comment:
The simplicity of these criteria will be appealing to clinical trialists because they provide a broad range of diagnoses for Alzheimer’s disease that can potentially be included in product labelling…A combination of biomarker level and clinical expression might be used to select patients who are transitioning through a specific phase that is hypothesised to be favourable to a drug being tested.
Although this lexicon is well integrated and conceptually attractive, field trials are needed to establish whether the diagnostic criteria will work effectively in clinical or research situations.
Prof Bruno Dubois MD, Prof Howard H Feldman MD, Claudia Jacova PhD, Jeffrey L Cummings MD, Prof Steven T DeKosky MD, Pascale Barberger-Gateau MD, André Delacourte PhD, Prof Giovanni Frisoni MD, Prof Nick C Fox MD, Prof Douglas Galasko MD, Prof Serge Gauthier MD, Prof Harald Hampel MD, Gregory A Jicha MD, Kenichi Meguro MD, John O’Brien DM, Prof Florence Pasquier MD, Prof Philippe Robert MD, Prof Martin Rossor MD, Prof Steven Salloway MD, Marie Sarazin MD, Leonardo C de Souza MD, Prof Yaakov Stern PhD, Pieter J Visser MD, Prof Philip Scheltens MD
The Lancet Neurology, Early Online Publication, 11 October 2010
doi:10.1016/S1474-4422(10)70223-4Cite or Link Using DOI
Written by Christian Nordqvist