The MDS Cognition Scale: a valid instrument for identifying and staging nursing home residents with dementia using the minimum data set.

OBJECTIVE: 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).
DESIGN: A Cross-sectional study. PARTICIPANTS: Two hundred nursing home residents. MEASUREMENTS: 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. MAIN
RESULTS: 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.
CONCLUSIONS: 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.