Decoding the DLB Diagnostic Criteria, # 1

This is the third time that the diagnostic criteria for dementia with Lewy bodies (DLB), first published in 1996, has been upgraded. But this is the first time that biomarkers have been added. Well, that's not quite right. Some of the tests were there, the DaT, for example, but the category of biomarker is new.

Even now, the only totally accepted objective test for most neurological diseases, including those in the Lewy body family, is via an autopsy. For years, doctors have diagnosed these diseases subjectively, via their educated guess about a person's reported symptoms. While Lewy-savvy doctors tend to be accurate compared to a later autopsy a high percentage of the time, the opportunities for mistakes with this kind of diagnosis are great.

A good diagnosis depended on the expertise of the doctor and the accuracy of the symptoms reported--when they were reported at all. An example of this were the Active Dreams that Annie had for years and were never reported to the doctor...or asked about. Of course, that was years ago, before the doctor knew to ask...but some still don't!

Enter biomarkers. These are objective tests that can be measured and repeated. None are yet accepted as 100% accurate, but that will come. In the meantime, they've made an accurate diagnosis much more likely, even when performed by less Lewy-savvy doctors.

However, until there is a biomarker that the experts can trust to provide a 100% accurate diagnosis, they are not going to say that any DLB diagnosis is totally accurate. Therefore, the criteria is still divided into Probable and Possible. The main change beside more focus on biomarkers is that two new symptoms have been added: the loss of smell and excessive daytime sleeping. (Hey! many of you exclaim...I knew that! Yes, but now it is there for the doctors to use as well.)

BTW, when we talk about diagnosis, we also get into an issue about what LBD, DLB and PDD mean. All the initials are confusing, but you can make it easy by noticing first initial in each case:

• LBD (Lewy body disease) is an umbrella term for all these two diseases caused by Lewy bodies.
• DLB (dementia with Lewy bodies) is the disease that starts with Dementia 
• PDD (Parkinson's disease with dementia) is the disease that starts with Parkinson's. 

If you are interested in the history of how the terms, Dementia with Lewy bodies, Parkinson's with dementia and Lewy body dementia evolved, read these 1/11/15 and 1/30/15 blogs.

Now, back to the 2017 criteria. First you may want to know why it is just for DLB and not for LBD as a whole. PDD has its own diagnosis, published by the Parkinson's community. It is structured and worded differently but says very similar things about the non-motor parts of the disease. The criteria for deciding if a person has DLB or PDD is arbitrary: If the movement symptoms occured at least a year prior to cognitive symptoms, it is PDD, otherwise, it is DLB. But there are some other differences. My guess is that as biomarkers get more efficient, we will have a more objective way to tell the two apart.

This diagnosis is written for doctors, not stressed-out care partners, or even retired nurses. I've had years of nursing experience and more years of doing dementia research--and I had to look my many of the words. An example was hyposmia, which I discovered was the loss of smell. Hypersomnia, was a little easier. I could figure out hyper (elevated) and somnia (sleep) but I still checked it out to find that it meant excessive daytime sleeping.

Therefore, this series of blogs will be a "decoding" of the criteria, starting with the first criterion. The original will be italicized, followed by definitions as needed and a rewritten version of the criteria "in plain English," also in italics. (The sections about symptoms aren't so filled with scientific gobbledy-gook but just wait until we get to the biomarkers!)

Essential Clinical Feature

Essential for a diagnosis of DLB is dementia, defined as a progressive cognitive decline of sufficient magnitude to interfere with normal social or occupational functions, or with usual daily activities.

• clinical feature: physical symptom
• progressive decline: ongoing, continually getting worse.
• cognitive: related to intellectual activity such as thinking, reasoning or memory.

In plain English: There must be evidence of cognitive loss great enough to interfere with social, occupational or daily living functions.

Prominent or persistent memory impairment may not necessarily occur in the early states but is usually evident with progression.

In plain English: Obvious or lasting loss of memory may not appear until later in the progression of the disease.

Deficits on tests of attention, executive function and visuo-perceptual ability may be especially prominent and occur early.

• deficits: lower than normal scores
• attention: the ability to focus, pay attention for a period of time without being distracted
• executive functions: thinking, reasoning, plan, learn, and other similar cognitive tasks
• visuo-perceptive ability: hand-eye co-ordination, depth perception and other vision-related tasks

In plain English: Cognitive skills related to attention, performing tasks, and visual perceptions are likely and tend to occur early in the progression of the disease.

Next week, we'll look at the Clinical Features, or symptoms. In the meantime, you can read the 2017 criteria for yourself. Feel free to ask questions. I'll try to answer them as I go along.

And here is another reminder about the differences between LBD, DLB and PDD and some of the words you will be seeing regularly in this series of blogs:

LBD is an umbrella term for all Lewy body diseases and starts with an L for Lewy.
DLB is for Dementia with Lewy bodies and starts with a D for the way the disease starts.
PDD is for Parkinson's disease with dementia and starts with a P for the way that disease starts.
Biomarker: Something measurable that can indicate the presence and severity of whatever you are testing for.
Indicative: A strong sign.
Supportive: A weaker sign that can still be helpful.
Probable Diagnosis: almost--but not quite!-100% accurate.
Possible diagnosis: Likely, but unproven without further evidence.

For more information about Lewy body disorders, read our books:
A Caregivers’ Guide to Lewy Body Dementia
Managing Cognitive Issues in Parkinson's and Lewy Body Dementia
Responsive Dementia Care: Fewer Behaviors Fewer Drugs
Riding A Roller Coaster with Lewy Body Dementia: A Manual for Staff

Helen and James Whitworth are not doctors, lawyers or social workers. As informed caregivers, they share the information here for educational purposes only. It should never be used instead of a professional's advice.