WHAT ARE THE OBSTACLES FOR AN ACCURATE CLINICAL-DIAGNOSIS OF PICKS-DISEASE - A CLINICOPATHOLOGICAL STUDY

Several studies have evaluated the reliability and validity of the cli nical diagnosis of Alzheimer's disease (AD) using well-defined neuropa thologic criteria, but none has attempted to evaluate the diagnostic a ccuracy of Pick's disease. We determined the accuracy of the clinical diagnosis of Pick's by presenting 105 autopsy-confirmed cases of Pick' s (n = 7) and related disorders (non-Pick's, n = 98) as clinical vigne ttes in randomized order to six neurologists who, were unaware of the autopsy findings. The group of raters had moderate to fair agreement f or the diagnosis of Pick's as measured by the kappa statistics. The se nsitivity for the diagnosis of Pick's for the first visit (mean, 53 mo nths after onset) and last visit (mean, 78 months after onset) was low (range, 0 to 71%), but specificity was near-perfect. Median positive predictive values at both visits were 83 to 85%. False-negative misdia gnoses mainly involved AD. False-positive diagnoses were rare and occu rred with corticobasal degeneration (first visit) and with dementia wi th Lewy bodies (last visit). Pick's was also misdiagnosed by primary n eurologists. The best clinical predictors for the early diagnosis of P ick's included ''frontal'' dementia, early ''cortical'' dementia with severe frontal lobe disturbances, absence of apraxia, and absence of g ait disturbance at onset. However, the first neurologic evaluation in some of the Pick's cases took place in advanced stages of the disease. Our findings suggest that this disorder is underdiagnosed in clinical practice. Although the low sensitivity for the clinical diagnosis of Pick's is disappointing, our data suggest that when clinicians suspect Pick's, their diagnosis is almost always correct. Absence of awarenes s of the main features of this disorder and of specificity of the fron tal lobe syndrome may partially explain the low detection of Pick's di sease.