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    Confusion reigns in testing for Alzheimer’s disease

    Eugen G Tarnow  May 24 2013 09:11:08 AM
    Confusion reigns in testing for Alzheimer’s disease (AD) due to ad hoc developments of tests, disagreement as to what constitutes a diagnosis of AD, and the lack of inter-disciplinary discourse.  

    Thus in a recent review article on screening methods for memory disorders, Ashford (2008) discusses the historically ad hoc development of cognitive tests for Alzheimer’s Disease (AD).  The most commonly used test, the Mini Mental State Exam (MMSE, Folstein et al, 1975), was developed in an evening (Folstein 1990).  The Selective Reminding Test (Buschke, 1973) was constructed to test not only short term memory but long term memory.  The rationale behind the test may be flawed since short term memory may last as long as 15 minutes (Tarnow, 2008 using data from Rubin et al, 1999).  If this is indeed the case, the test joins the MMSE in being effective but ad hoc.  A third test, the FCSRT was patented by Buschke (1999) to calculate a weighted average of the probability of recall in which the weights change with presented item order.  His method can be characterized as ad hoc in that he did not use a well defined method to arrive at the weights but looked at the curves and guessed.

    Moreover Alzheimer’s disease (AD) is a controversial disease (Whitehouse & George, 2008). A recent NIH consensus statement (Daviglus et al, 2010) declared that “highly reliable consensus-based diagnostic criteria for cognitive decline, mild cognitive impairment, and Alzheimer’s disease are lacking” and Beach et al (2012) found that 40% of patients not diagnosed with AD were found to have AD at autopsy and 17%-30% of those diagnosed with AD did not have it at autopsy.  Thus when tests for AD are developed, the AD diagnosis is unreliable which, of course, makes the tests unreliable as well.  The Blessed Information-Memory-Concentration (Blessed et al, 1968) is the only test that has autopsy validity – it is correlated with the neurofibrillary tangle counts of dementia patients that are not severely demented.

    Finally, the communication in the AD field is non-optimal.  Data sharing is hampered by the perceived profit potential (Koslow, 2002).  Competing research groups do not cite each other (I will not embarrass the authors by declaring names).  AD is by its complexity a multidisciplinary effort but efforts in one field sometimes is ignored by another.  For example, neurology seems to ignore psychology: a consensus in neurology (McKhann et al, 2011) chooses not to include specific memory information from neuropsyhology that is known to lead to an initial diagnosis of AD and  Wright & Zonderman (2013) write that “inexpensive and noninvasive screening measures with both good sensitivity and specificity are needed” even though groups associated with both Ashford and Grober claim to have such tests for many years now and Ashford provides a list of 20 manual tests and 18 computerized tests.

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