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Interrater agreement for diagnosis of Alzheimer's disease: the MIRAGE study
L A Farrer1, L A Cupples, S Blackburn
1Department of Neurology, Boston University School of Medicine, MA 02118.
Abstract:
There are standardized criteria to assist in the diagnosis of Alzheimer's disease (AD), a disorder that lacks unique clinical, morphologic, or biochemical features. Diagnostic reliability of single groups of investigators using these criteria is moderate to substantial. In this study, seven clinicians at separate sites established a criteria-based diagnosis in 42 consecutive memory disorder patients participating in a national genetic epidemiologic study using a quantitative multiaxis AD rating scale (ADRS) that incorporates NINCDS/ADRDA criteria, reliability of information, and comorbidity. Reliability, measured by a generalized kappa statistic for more than two raters, was substantial (0.63 +/- 0.13) when the subjects were grouped as "AD" (probable or possible) versus "not AD," but somewhat lower (0.52 +/- 0.10) when subjects were classified as probable AD, possible AD, or not AD. There was unanimous agreement for two-thirds of the subjects using a dichotomous classification scheme. These findings suggest that the ADRS is a useful diagnostic instrument for multicenter studies.
Insights
Diagnosing Alzheimer's disease (AD) is challenging due to its non-specific features. A new rating scale showed substantial reliability among clinicians in multicenter studies for diagnosing AD.
Area of Science:
- Neurology
- Clinical Diagnostics
- Epidemiology
Background:
- Alzheimer's disease (AD) diagnosis lacks unique biomarkers, relying on standardized criteria.
- Previous diagnostic reliability using these criteria has shown moderate to substantial agreement.
- Multicenter studies require reliable diagnostic instruments for accurate patient classification.
Purpose of the Study:
- To evaluate the diagnostic reliability of a quantitative multiaxis Alzheimer's Disease Rating Scale (ADRS).
- To assess the utility of the ADRS in a national genetic epidemiologic study involving multiple clinicians.
- To determine inter-rater reliability for classifying patients with and without Alzheimer's disease.
Main Methods:
- Seven clinicians at separate sites diagnosed 42 memory disorder patients using the ADRS.
- The ADRS incorporates National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS/ADRDA) criteria, reliability, and comorbidity.
- Generalized kappa statistic was used to measure inter-rater reliability.
Main Results:
- Substantial reliability (kappa = 0.63 +/- 0.13) was achieved when grouping subjects as "AD" versus "not AD."
- Reliability was somewhat lower (kappa = 0.52 +/- 0.10) when classifying into probable AD, possible AD, or not AD.
- Unanimous agreement was reached for two-thirds of subjects using a dichotomous classification.
Conclusions:
- The Alzheimer's Disease Rating Scale (ADRS) demonstrates substantial reliability for diagnosing Alzheimer's disease in multicenter settings.
- The ADRS is a valuable tool for improving diagnostic consistency in large-scale research studies.
- The scale aids in classifying patients, supporting epidemiological research on Alzheimer's disease.