Decoding the DLB Diagnostic Criteria, #5: Formula

This is the last of five blogs about the 2017 diagnostic diagnosis of dementia with Lewy bodies (DLB), a document written for doctors but one which even stressed-out care partners should know about. Thus, over the last month, we've attempted to "decode" its language and present a more care partner-friendly version. In this last blog, we find out how to use these symptoms to identify the likelihood of Probable or Possible DLB. Although this section seems easier to read than other sections, I've still added an "In plain English" segment just for continuity.

The publishers of the criteria use a formula to identify Probable or Possible DLB, and to rule it out to a certain extent. As always, they are careful to never say "always" or "never"!

Probable DLB can be diagnosed if:

• two or more core clinical features of DLB are present, with or without the presence of indicative biomarkers,
or
• only one core clinical feature is present, but with one or more indicative biomarkers.

Probable DLB should not be diagnosed on the basis of biomarkers alone.

In plain English: Probable DLB can be diagnosed by the presence of a) least two core symptoms with or without biomarkers or b) one core symptom with at least one indicative biomarker but not by biomarkers alone.

Possible DLB can be diagnosed if:

• only one core clinical feature of DLB is present, with no indicative biomarker evidence,
or
• one or more indicative biomarkers is present but there are no core clinical features.

In plain English: Possible DLB can be diagnosed by the presence of a) at least one core symptom or b) one indicative biomarker.

The criteria also adds this:

DLB is less likely:

• in the presence of any other physical illness or brain disorder including cerebrovascular disease, sufficient to account in part or in total for the clinical picture, although these do not exclude a DLB diagnosis and may serve to indicate mixed or multiple pathologies contributing to the clinical presentation,
or
• b) if parkinsonian features are the only core clinical feature and appear for the first time at a stage of severe dementia.

In plain English: DLB is less likely in the presence of another physical illness or brain disorder with similar symptoms, although both it and DLB could be present. It is also less likely if the only core symptoms are movement issues that appear only after severe dementia is present.

Note that neither suggestive symptoms nor suggestive biomarkers are not included in these formulas. They simply add weight to a diagnosis. However, as care partners, recognizing these symptoms can definitely signal the need to see a doctor.

For more information, download the 2017 DLB Diagnostic Criteria if you haven't already done so. Also, find lots of information about the various symptoms in our books.

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.