Diagnostic challenges of using CSF assay of tau and beta-amyloid(42) in atypical XXXX of the Alzheimer type.

@entity1 @entity2204 @entity303 @entity195 @entity8637 @entity385
This report presents three cases of atypical @entity303 in order to illustrate challenges associated with the use of biologic markers of @entity195 ( @entity195 ) for diagnosis and management. Clinical diagnostic methods followed the NINCDS-ADRDA criteria for @entity195 . Additional diagnostic studies included serial neurocognitive testing, MRI, neuroSPECT, @entity2204 genotyping, and a CSF assay of tau and beta-amyloid(42). For @entity1 1, both the clinical and biologic markers were consistent with @entity195 . The @entity1 was diagnosed with @entity195 with a high degree of confidence, even though the base rate of nonfamilial @entity195 at this age group (<55 years) is exceedingly rare. This case argues favorably for the use of biologic markers to aid in confirming a diagnosis in an atypical @entity303 . @entity1 2 met the NINCDS-ADRDA criteria for @entity195 , although with less confidence. Neurocognitive data indicated a progressive @entity385 , insight was preserved, and @entity2204 was 3/3, but tau concentrations and beta-amyloid(42) were highly consistent with cut-offs for @entity195 ; the differential fell on the @entity8637 's disease/frontotemporal degeneration spectrum. @entity1 3 had no clinical evidence of the disease, even when evaluated via extensive neurocognitive testing over a 2-year interval. However, @entity2204 was 4/4, and CSF assay of tau and beta-amyloid(42) were within the @entity195 range. Therefore, while the CSF assay of tau and beta-amyloid(42) markers was confirmatory of @entity195 , each case was highly atypical. Results illustrate the lack of normative data available when using biologic markers for highly atypical cases, calling into question their usefulness for such @entity1 . These cases illustrate the interplay between neuropsychological and biological markers in establishing neurodegenerative diagnoses.
