The validity of the minimum data set in measuring the cognitive impairment of persons admitted to nursing homes

This study examined the construct validity of two cognitive scales from the federally mandated Minimum Data Set (MDS) of the nursing home Resident Assessment Instrument.

A cross-sectional comparisons of the MDS measures, with scales provided by the resident, a proxy person, and nursing staff.

Subjects residing in 59 nursing homes (NHs) in Maryland from 1992 to 1995.

Subjects were 1939 new admissions to NHs, aged 65 and older, with complete MDS information at admission.

Two MDS scales, the Cognitive Performance Scale (CPS) and the MDS Cognition Scale (MDS-COGS), were compared with the Mini-Mental State Examination (MMSE) and the staff rating on the Psychogeriatric Dependency Rating Scale (PGDRS) Orientation scale, as well as measures of functioning and functional decline.

The CPS and the MDS-COGS were highly correlated (r = 0.92). Both correlated moderately well with the MMSE (r = -0.65 and -0.68) and with staff's rating on the PGDRS Orientation scale (r = 0.63 and r = 0.66). Correlations with the MMSE (r < 0.70) are lower than previously reported (r > or = 0.80). The proportion of cognitively impaired residents in this NH admission cohort was higher using the MDS-COGS than the CPS (65% vs 57%), but both MDS scales produced lower proportions than the MMSE (70%) and higher proportions than the PGDRS (47%). The internal consistency of the CPS was better without the comatose item (alpha = 0.80 vs 0.70). The MDS-COGS had higher internal consistency (alpha = 0.85) and was simpler to compute.

This is the first study to examine the validity of the MDS in a large sample of residents and NHs in situations where the MDS was not completed by research-trained staff. Compared with other instruments, the MDS-COGS and the CPS had moderate and similar validity for assessing cognitive impairment. Differences in the scales could provide different estimates of impairment among persons admitted to nursing homes.