Alzheimer’s Tests Working Together

Alzheimers disease tests may work best when they are combined

/ Author:  / Reviewed by: Robert Carlson, M.D

(RxWiki News) Medical tests for Alzheimer’s disease (AD) may help with early diagnosis, but no test is perfect. A recent study found that conducting multiple tests together improved the accuracy. But is this expense worth it?

The study tested people with mild cognitive impairment (MCI) to see when they developed AD. They did two different brain scans, a test of spinal fluid and mental skills tests. 

They found that using all the tests together lowered the rate of error by about a third.

"Ask a doctor if testing is right for you."

Researchers led by Jennifer L. Shaffer, MD, of the Department of Radiology at Duke University, wanted to know if adding more tests would better detect when people move from MCI to AD. They enrolled 97 patients with MCI who had memory and thinking problems that are not as severe as AD. People with MCI have a high risk of developing AD. They did a series of medical and mental skills tests with the patients.

Magnetic resonance imaging (MRI) was used to look at brain tissue loss. A positron emission tomography (PET) scan was used to look at brain function.

They also took spinal fluid and tested for levels of tau and beta amyloid – both proteins that are known to build-up in the brains of people with AD. Standard clinical tests were also used, which included mental skills tests, dementia tests and looking for risk factors like age and family history.

The patients were tested once or twice a year for up to four years. Then they looked to see which tests were the best at detecting when patients moved from MCI to AD.

They found that clinical tests were the least accurate

Adding MRI, PET and spinal fluid tests to the clinical tests increased the accuracy.

The number of people who were falsely diagnosed with AD decreased from 41.3 percent with clinical measures alone to 28.4 percent when all the tests were used together.

The PET scan, more than the spinal fluid tests or MRI, helped with accuracy when combined with clinical testing. In other words, if only one medical test was used for diagnosis, the PET added to the clinical measures was best.

The authors concluded that if they can’t all be used together, the PET with the clinical tests were the most accurate way to diagnose AD in patients with MCI.

PET, MRI and spinal fluid tests are more expensive and time consuming than clinical measures. Using them all together is probably not practical or cost effective.

An MRI can cost up to $5,000. PET scans can cost up to $1,000. Both of these tests would need a person specially trained in AD diagnosis to interpret the scans, which adds to the total cost.

There are currently no treatments that can slow the progression of AD. Using these costly tests could give information but cannot help doctors to treat patients with AD.

However, an early diagnosis may help people better prepare for the way AD will affect their lives. Knowing a diagnosis may also help people watch for and manage their symptoms.

This study was published December 11 in Radiology. The study was funded by grants from the National Institute of Mental Health and the National Science Foundation. Some study authors received funding from the Alzheimer’s Disease Neuroimaging Initiative, which is funded by government grants and support from major pharmaceutical companies. Authors on this study also report direct financial affiliations with numerous pharmaceutical companies.

Reviewed by: 
Review Date: 
December 5, 2012
Last Updated:
December 11, 2012