Towards a simpler, more reliable Alzheimer's diagnosis

Date: Jul-04-2014Alzheimer's disease is the most common form of dementia - a syndrome that affects

memory, thinking, behavior and autonomy. Yet getting a reliable, early diagnosis for Alzheimer's

is not easy - more than 1 in 3 patients receive an incorrect diagnosis. Now an international

team of researchers that has spent 10 years working towards a simpler, more reliable approach to

the diagnosis of Alzheimer's disease, reveals its proposals in a Position Paper published in the

journal The Lancet Neurology.

According to the World Health Organization, the number of people with dementia is expected to double by 2030 and more than triple by 2050.

According to the World Health Organization, worldwide there were around 36 million

people with dementia in 2010, and this number is expected to double by 2030, and more than triple by

2050.

About 70% of dementia cases are Alzheimer's - a brain-wasting disease caused by loss of brain

cells that become damaged when faulty proteins accumulate inside and around them. As the

behavioral and cognitive symptoms of Alzheimer's disease overlap with other forms of dementia,

clinicians and researchers are faced with real challenges when it comes to making a reliable

differential diagnosis - especially in the early stages.

In 2005, an international group of neurologists redefined a set of diagnostic criteria for

identifying patients with Alzheimer's. Until then, it had been necessary to wait for patients to

die before establishing a diagnosis by autopsy. The most that could be done for living patients

was to estimate the probability of them having Alzheimer's, and then only in the late stages of

the disease, which was decided based on severity of dementia.

Introduction of biomarkers transformed diagnosis of Alzheimer's

And then in 2007, the group transformed the diagnostic criteria by introducing the idea of

biomarkers. For the first time, there was the possibility of diagnosing Alzheimer's more reliably

in living patients using biological disease signatures that are present in the early stages.

When they revealed their new diagnostic criteria they caused a sensation. One group of

researchers declared that "36% of their patients included in a therapeutic trial based on previous

clinical criteria did not have Alzheimer's disease," says Bruno Dubois, a professor of neurology

at the French biomedical and public health research institution Inserm, and co-ordinator of the

2007 group.

Prof. Dubois, who is also first author of the new paper, goes on to explain that the

implications of such a discovery were serious - patients were not receiving the right care or

treatment, and poor selection of participants is likely also to have led to flawed conclusions

about treatment effectiveness.

New Alzheimer's diagnostic criteria are 'more refined'

Things have moved on significantly since 2007, causing the group to revisit the diagnostic

criteria for Alzheimer's in the light of new studies. The Position Paper marks "the end of the

road," says Prof. Dubois, who adds: "we have arrived at the essence, something refined, resulting from an

international consensus."

The group has not only arrived at what it believes is a more reliable algorithm for diagnosing

Alzheimer's, but a much simplified one too, that relies on "just a couple of clinical-biological

criteria for all stages of the disease," explains Prof. Dubois.

The method is in two parts: a suggestive clinical picture that can be one of three scenarios

(typical, atypical, and preclinical), and a biomarker.

In 2007, for the first time, there was the possibility of diagnosing Alzheimer's more reliably in living patients using biological disease signatures that are present in the early stages.

The group suggests most of the time, the diagnosis of Alzheimer's will be based primarily on a

suggestive clinical picture that is then subsequently confirmed or rejected using one of the two

biomarkers.

The three scenarios of the suggestive clinical picture are:

Typical cases (expected to be 80-85% of cases): brain changes that lead to problems with

episodic long-term memory, including difficulty remembering a list of words, even with hints
Atypical cases (15-20% of cases), brain changes that cause problems with verbal memory and

other behavioral problems
Preclinical states, where patients do not appear to have symptoms, but for some reason - for

instance from taking part in a trial - are discovered to have biomarkers or gene mutations for

Alzheimer's.

The two biomarkers - only one of which is required to confirm or reject the suggestive clinical

picture diagnosis - are:

Abnormal levels of brain proteins in cerebrospinal fluid (higher levels of tau and reduced

levels of beta amyloid protein). The fluid is obtained by lumbar puncture

PET (positron emission tomography) brain scan that shows higher retention of an amyloid

tracer.

Meanwhile, Medical News Today recently learned of a new diagnostic tool to help

clinicians differentiate between

Alzheimer's disease, frontotemporal dementia and mild cognitive impairment. The software-based

tool is a new combination of various methods for the differential diagnosis of Alzheimer's and the

other two conditions, and comprises a Disease State Index that draws from multiple sources such as

psychological tests and brain MRI, and a visual counterpart, a Disease State Fingerprint.

Written by Catharine Paddock PhD

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.