August 10th, 2010
01:59 PM ET

Study shows testing for Alzheimer's is accurate

By Dr. Sanjay Gupta
CNN Chief Medical Correspondent

Even back when I was a medical student, we were taught Alzheimer’s disease (AD) began to cause damage in the brain years, perhaps decades before one’s memory started to fade.

The big question, of course, was how could you possibly screen for the disease before problems emerged? As things stood for a long time, the only way to know for sure if someone had AD was at the time of autopsy. In fact, the disease is named after Alois Alzheimer, a neuropathologist, who in 1906, diagnosed the disease by using special stains of the brain after a patient’s death.

Over the years, there have been sophisticated tests such as PET and MRI scanning, which can help diagnose a patient, but are often better at excluding other causes of memory loss rather than confirming early AD. In short, there has been no great screening test for Alzheimer’s disease.

That may all start to change today, based on a new study from the Archives of Neurology.  The authors have conducted a study showing a spinal-fluid test can be nearly 100 percent accurate in identifying patients who have mild memory loss now, and will go on to develop AD.

Think about that for a second.  I have seen so many patients with mild memory loss who ask the question – is this the beginning of Alzheimer’s disease?  The truth is, as a medical community – we were not sure.  This test could provide that answer.

The study of patients in their seventies, included 114 patients with normal memory. 200 had mild cognitive impairment and 102 had been diagnosed with Alzheimer’s disease.  All of them underwent a spinal tap to collect cerebrospinal fluid (CSF), a procedure that costs anywhere between $300 and $500. It involves putting a needle in the spinal sac in the lower back.  Women who have had an epidural during labor have experienced a procedure similar to this.

Almost all the patients with AD were found to have a distinctive collection of protein in their CSF, a sort of AD signature.  That is: The spinal tap was very good at confirming someone did in fact have the disease.  But it was the group of people with mild cognitive impairment that provided the most striking findings.  Nearly 75 percent of those patients in the study had the signature CSF findings, and every single one of those patients went on to develop AD within five years. Every single one of them.

In the third group, the patients with normal memory, around one third of those patients had the abnormal proteins, and the authors believe those people will develop AD memory problems one day as well.

This study, which will need to be duplicated, seems to indicate if you have an abnormal test result with the spinal tap, you will develop Alzheimer’s Disease. It is just a question of when. It is also important to point out that no one can say a normal test result necessarily puts you in the clear and some people may have slightly abnormal test results without developing AD.

Nearly 20 years after I finished medical school, we are on our way to an effective screening test.  Still, I would be remiss if I didn’t point out that nowadays, there aren’t great options for prevention or treatment of Alzheimer’s disease.  Sure, researchers are optimistic we will get there soon, but not as things stand now. So, the bigger question for a lot of people is: Even if the spinal tap becomes a proven, effective screening test for AD – “would you really want to know, if there isn’t much you can do about it?”

soundoff (107 Responses)
  1. Oh Wow

    I would like to know how many cases of "early onset" (or later onset, for that matter) Alzheimers are actually caused by "mad cow" prions. I hope they can find a cure for both.

    August 11, 2010 at 08:59 | Report abuse | Reply
  2. The value in knowing

    My mother is completely debilitated with early-onset alzheimer's and, unless you've been in this sort of situation, you'd be surprised how heavily the prospects of inheritance can weigh on you. I haven't decided what to do regarding testing for myself, but I can definitely see the value in knowing. Others have highlighted the value in knowing that you DO have the early markers for the disease- planning, living to the fullest, etc. But the even greater value to me would be in knowing that I DON'T have the early markers- it would be very liberating to know that every little memory lapse isn't the calm before a storm but rather exactly that- just a little normal memory lapse. The suspicion without knowledge can really erode your confidence. My $0.02.

    August 11, 2010 at 10:28 | Report abuse | Reply
  3. bob in calif

    Since both my mother and her sister died with Alzheimer's, I would like to know. It would enable me to plan better for end of life issues. It would also somewhat change how much I spent on travel each year.

    August 11, 2010 at 11:46 | Report abuse | Reply
  4. bobbie

    So.....what if you could have a test prove to you that you DO NOT have to worry about Alzheimers? My mom died of dementia – although it was not diagnosed as Alzheimers specifically. I am 64 and in perfect health with a perfectly functioning memory – I would give A LOT to know that I had been spared.

    August 11, 2010 at 11:51 | Report abuse | Reply
  5. ccsm

    My mother, who is 70, was examined at a very highly respected medical facility in Durham, NC one year ago and was told that she had AD, based on a series of questions. This news was devastating to the entire family. Her mother had already passed away from AD years earlier. Mom was definately showing signs of short term memory loss and exhibiting agressive behavior, which was taking its toll on my father as her care giver. Long story short, the family made the decision to have her enter a skilled nursing facility that specializes in AD, a decision that was very difficult to make. We are now 5 months down the road with mom still at this facility, and she has completely turned around for the better. She was diagnosed with having bipolar, which accounted for the crazy behavior and mood swings. She is on medication to treat the bipolar as well as taking Aricept and Nameda for AD. The doctors have said that they feel she does have some demetia, but her moods have stablized from the drugs for the bipolar, and she should be able to return home, which is great news. Months ago we were told that she was in stage 4 AD and would never be able to go home again. So I share ths story with all of you to point out that it is important to have your loved one accurately diagnosed because there could be an underlying mental illness that is not being treated. We all knew she has suffered from depression all her life, but never knew she was now bipolar. And if in fact she does have AD, and we all know the sad future that lies ahead, at least by getting the proper treatment for the other illness I know that she will be able to enjoy some quality time at home in her own surroundings until the AD takes over.

    August 11, 2010 at 13:59 | Report abuse | Reply
  6. milenkovic

    To me, its worth the $500. I have huge responsibilities as head of household, and have a incontrovertible need to know.

    August 11, 2010 at 15:47 | Report abuse | Reply
  7. Claire

    Whether or not they can cure it now, it would be great to be part of a study that may help find a cure for this horrific disease. I don't have it in my family, but some of the 90+ year-old men have developed senile dementia. I'd definitely like to find out if it's genetic and see if other dementias also can be predicted.

    August 12, 2010 at 05:06 | Report abuse | Reply
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    August 12, 2010 at 07:05 | Report abuse | Reply
  9. Mark

    The problem with first generation tests like this one is that is needs more study and global clincial testing. The "a sort of AD signature" is exactly where they are and I suspect false negatives and false positives will come out of 1st generation testing. For example, thryoid testing started wtih PBI, then T4 (due to PBI being inaccurate), then T7 (due to T4 being inaccurate), then TSH (and so on) and now on it's 6th generation of TSH version testing. Even though this is blood versus spinal fluid– many neurological CSF tests have gone through various generations of tests.

    In the meantime, it really doesn't yield anything, you don't know when it's going happen, could be 5, 10 or 15 years, who knows. You can't treat it. They came out with a experimental test for Chronic fatigue sydrome years ago that looks for a particular marker, everybody went for the test and people who are not even sick tested postived, people who were sick test positive and others test negative.

    So folks, in my opinion, were still in the cave on this and probably will be for a long time.

    August 14, 2010 at 21:26 | Report abuse | Reply
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    September 11, 2010 at 07:54 | Report abuse | Reply
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    I've heard exciting things about marijuana and Alzheimer's and I hope more research is done to see what benefits marijuana might offer (preventative vs reactive too)

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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.