The MDS Cognition Scale: A Valid Instrument for Identifying and Staging Nursing Home Residents with Dementia Using the Minimum Data Set

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Abstract
We report the development and validation of an MDS-based cognitive index, the MDS Cognition Scale (MDS-COGS), by evaluating it against two popular dementia rating scales, the Global Deterioration Scale (GDS) and the Mini-Mental State Examination (MMSE). A Cross-sectional study. Two hundred nursing home residents. Each study participant was assessed on the GDS and the MMSE by trained medical students. At the same time, but independent of the medical students, a geriatric nurse completed the Minimum Data Set (MDS) instrument on each participant. The Cognitive Performance Scale (CPS), a categorical measure of cognition that uses MDS items, was compared with the GDS in 133 subjects, using a split-sample technique. The GDS was found to be more appropriate as a 4-stage than a 7-stage scale, with GDS stages 1-4 acting as a single stage. The CPS showed very poor percent agreement with GDS stages 5 and 7 (50% or less) and, therefore, was revised by adding other MDS predictors. The new instrument, designated MDS-COGS, is a 0-10 point scale generated from eight MDS cognitive items. The MDS-COGS was then validated against the 4-stage GDS and MMSE in the remaining 67 nursing home residents. Chance-corrected agreement (kappa) between the MDS-COGS and GDS in the 67 subjects was 0.80 (95% CI = 0.70, 0.88), and percent agreement with GDS stages 5 and 7 was 60% and 85%, respectively. The MDS-COGS was also demonstrated to be a valid measure of cognitive impairment as defined by the MMSE, with sensitivity, specificity, chance-corrected agreement (kappa), and area under the ROC curve, all above 0.80. The MDS Cognition Scale, the MDS-COGS, provides a valid measure of the presence and severity of cognitive impairment in nursing home residents using items from the Minimum Data Set.