In the
September 2011 issue of the Archives of General Psychiatry (reference),
Dr. Goldberg and colleagues report the results of the first study that examined
the respective predictive values of cognitive measures, brain imaging, and
cerebrospinal fluid (CSF)
biomarkers in determining the risk of conversion from Mild Cognitive Impairment
(MCI) to
Alzheimer’s disease (AD).
In
contrast with the multiple recent publications derived from the Alzheimer’s
Disease Neuroimaging Initiative about biomarkers in AD (ADNI; see
earlier post), this work identified measures of delayed verbal memory (Logical
Memory delayed recall and Auditory Verbal Learning Test delayed recall) as the
most reliable predictors of progression from MCI to AD. While brain volume assessed by MRI (Left
middle temporal lobe thickness) was identified as an additional predictive
factor, the levels of Ab42 and Tau in the CSF did not add significant
predictive value to their model (systematic stepwise logistic regression).
In
commentary provided to Medscape (link), the lead author urged
caution in interpreting this finding by stating that “Biomarkers unarguably
work. However, cognitive markers, which are less expensive and less invasive,
also work and provide strong complementary information”.
In my
mind, the question is not so much whether cognitive assessment tools work
better than CSF biomarkers but more about the applicability of these findings
to the general practice of medicine.
Indeed, while CSF biomarkers are objective measures, the results of even
the best cognitive tests are partially subjective: the skills of the person
administering the test can have an influence on the results. Therefore, one can wonder if, in the hands of
the average neurologist or neuropsychiatrist, the verbal
memory testing would perform as well and would outperform the objective measure
provided by CSF biomarkers.
Thierry
Sornasse for Integrated Biomarker Strategy
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