The development of biological markers for the diagnosis of Alzheimer's disease

Linear width of the medial temporal lobe can discriminate Alzheimer’s disease from normal aging: the Sunnybrook Dementia Study

To discriminate Alzheimer's disease (AD) from healthy controls, the thinnest medial temporal lobe (tMTL) width on 3D-MRI was measured according to a newly developed method at the inter-collicular sulcus (ICS) level with scans aligned to the long axis of the hippocampus in 22 mild, 27 moderate probable AD patients and 41 healthy controls. For comparison, MTL width replicating the technique of Jobst et al. (jMTL) as well as hippocampal and parahippocampal volumes, were also measured. Using logistic regression taking into account age, sex, and education, tMTL width classified mild AD from controls with a sensitivity of 86%, specificity of 95% and accuracy of 92%. Similar values were obtained for moderate or total AD group versus controls. By comparison, jMTL width was only useful in distinguishing moderate AD from controls, and volumetric measures were equally sensitive in classifying mild and moderate AD in our sample. This quick, reliable, and standardized measurement of tMTL can be helpful in differentiating even mild AD from controls with reasonable accuracy.

Diagnostic approaches to Alzheimer's disease

The importance of obtaining an accurate and early diagnosis for Alzheimer's disease is now becoming recognized. Nonpharmacological as well as pharmacological therapies can be best initiated once a diagnosis is obtained. Biochemical markers to identify Alzheimer's disease have been sought for many years, with many candidates proposed. Recently criteria were established to evaluate putative diagnostic tests. Several biomarkers now show utility in identifying those with Alzheimer's disease. The ApoE e4 allele, while a risk factor rather than a deterministic gene, in the context of an individual with suspicion of AD has a positive predictive value of 94-98% and may come to have utility in predicting response to certain classes of pharmacological agents. Independent groups have shown that the markers in cerebrospinal fluid tau and Ab42 are, respectively, elevated and reduced in patients with AD versus other patient groups and that the lumbar puncture itself is usually well tolerated. For early-onset AD, sequencing presenilin 1 has come into use and the positive frequency is similar to that found in other genetic-based laboratory tests.

Balanced centralized and distributed database design in a clinical research environment

Clinical research databases can meet both research and clinical needs, but this ideal is seldom achieved. Priorities often differ for those who collect and ultimately use the data and those who develop data systems. Traditional database designs also create logistical barriers that hamper communication. The Michigan Alzheimer's Disease Research Center has developed a secure, distributed data system with centralized data entry that provides an intuitive, individually customized interface for investigators in their clinics, laboratories and offices. Data are kept in a form that can be readily understood without reference to a code-book. Investigators can modify and query their own copies of the database without knowledge of programming languages. Balancing centralized and distributed designs for research databases enhance the accuracy and completeness of data collection and increases the use of data for research and clinical care.

Mitotic index and Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is diagnosed definitively by increased numbers of beta-amyloid plaques and neurofibrillary tangles in brain biopsy or autopsy specimens. There are no simple straightforward laboratory tests currently available for clinical diagnosis. We have found consistent reduction in mitotic index levels in skin fibroblast cultures from AD individuals compared with age- and sex-matched controls. These differences were enhanced by overnight exposure to colcemid (p = 0.04). Results suggest that mitotic index in skin fibroblasts cultures should be further investigated as a potential diagnostic indicator for AD.