Diagnosis Research

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MINDY KIM-MILLER, MD, PhD
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Question:

My mother was finally diagnosed with Alzheimer’s disease after weeks of testing and seeing various doctors. It seemed like the doctors had to figure out what she didn’t have before they could figure out what she did have. Why is it so hard to diagnose Alzheimer’s disease? Is there hope of finding a better way to diagnose the disease?

–Sarah, 51, Austin

Answer:

Diagnosing Alzheimer’s disease (AD) can be challenging, because many other diseases and medical conditions can cause similar symptoms. Your mother’s physician is doing the responsible thing by investigating all the possible causes of memory and behavior symptoms. AD is a diagnosis of exclusion, meaning that many other possible causes of dementia have to be excluded before the diagnosis of AD can be made with any certainty. At this time, the only way to make a diagnosis of AD with 100% certainty is by a brain biopsy, which is done after death if at all. There is a clear need for better ways to test for the disease, and many researchers have taken on this challenge.

An exciting area of research involves testing the blood for signs of the disease. Researchers are looking for abnormal levels of certain substances in the blood of people with AD or mild cognitive impairment (MCI) compared to people without cognitive problems. One of the difficulties with many forms of dementia is that by the time the symptoms are noted, the disease has already been damaging the brain for some time. These new tests would be useful in identifying people who are already developing the disease years before symptoms appear. One blood test being developed examines the levels of 18 different substances in the blood and appears to predict the development of AD in those with MCI with 90% accuracy. Early diagnosis would allow early intervention to try to delay the onset or progression of symptoms.
Blood tests are easier to do and, in some cases safer and more comfortable for the patient, than many other tests currently used in diagnosing AD, such as spinal fluid tests. A blood test would also make it easier to follow the progress of the disease and to conduct research. There may soon be diagnostic blood tests for AD and MCI.
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Another promising area of research is the use of neuroimaging (pictures of the brain). Neuroimaging can be used to study the level of brain activity (functional neuroimaging such as MRI and CT) and brain anatomy (structural neuroimaging such as PET, fMRI and SPECT). In those with AD or other dementias, certain areas of the brain show decreased levels of activity or have smaller volumes compared to normal brains. Some of these findings have already been put into clinical use. For example, positron emission tomography (PET) measures the uptake of sugar in the brain, which is one way of measuring activity. PET imaging significantly improves the accuracy of diagnosing AD from frontotemporal dementia compared to the usual tests used in diagnosis. In fact, Medicare pays for PET scans performed to help distinguish AD from frontotemporal dementia. There is ongoing research to refine neuroimaging techniques and improve the accuracy of diagnosing AD and other dementias.The development of such new diagnostic tests will help physicians correctly diagnose AD and facilitate early intervention and decrease the chance of prescribing the wrong medications or improperly hospitalizing people. Better diagnostic tests will also decrease the stress, time and money spent by patients and their families on unnecessary tests or living with an uncertain diagnosis.

Dr. Mindy Kim-Miller is a trained medical physician who provides useful, but general answers to questions provided by online visitors. While Dr. Mindy can not provide specific medical advice or services, we hope you find her responses useful in your personal education. All information is provided for informational and educational purposes only and is not meant to be a substitute for professional medical advice, diagnosis or treatment. If you suspect you have an illness or disease, or a health related condition of any kind, seek professional medical care with an appropriate health care professional immediately. Do not postpone or delay seeking treatment or disregard professional advice based upon the general answers provided by Dr. Mindy. Dr. Mindy’s advice is not intended to substitute for a visit to your personal physician or other qualified health provider. Any specific medical concerns or questions you may have should be directed to your personal physician or other qualified health provider.

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