Inter-rater reliability of the diagnosis of vascular cognitive impairment at a memory clinic

Consensus criteria for the diagnosis of vascular dementia (VaD) are gradual ly being replaced with data-based criteria. We report the inter-rater relia bility of a new set of empirically-derived criteria for vascular cognitive impairment (VCI). Stratified sampling, with optimal allocation, was employe d to randomly select 36 patients from the Queen Elizabeth II Health Science Centre's Memory Disability Clinic. Chart reviews were conducted independen tly by 4 physicians. Each physician classified the patients as having eithe r: no cognitive impairment, VCI or Alzheimer's disease (AD). VCI was furthe r classified both clinically (VCI without dementia, VaD or AD with a vascul ar component) and radiographically (infarcts, white matter changes, single strategic stroke). The intraclass correlation coefficient (ICC) for the dia gnosis by physicians of VCI or otherwise was based on a repeated-measures a nalysis of variance with raters as the independent variable. A significant coefficient of reliability (average ICC = 0.88, 95% CI = 0.80-0.93) was obt ained (H-o: rho less than or equal to 0.80, p = 0.03). Where differences in diagnosis occurred, the discrepancies most commonly resulted within the su btypes of VCI (9 cases) or between the diagnoses of AD and VCI (9 cases). I nstances of diagnostic incongruity were typically due to the disagreement o f a single rater (10 cases). This study demonstrates a high degree of relia bility of criteria for VCI by physicians in a memory clinic, and can also b e understood as an aspect of construct validation of those criteria. In the absence of a readily available biological marker for VCI, clinical criteri a are necessary and can be reliably employed. Copyright (C) 2000 S. Karger AG, Basel.