Differential item functioning in the short portable mental status questionnaire

Abstract

This secondary data analysis investigated differential item functioning (DIF) in the Short Portable Mental Status Questionnaire (SPMSQ) across demographic subgroups. The study was conducted at an academic primary care group practice on 3,954 patients aged 60 years and older who completed the SPMSQ during routine office visits. After adjusting for overall cognitive ability, women were more likely than men to respond correctly to name-of-this-place and mother's-maiden-name items. African Americans were more likely than Whites to correctly give their correct telephone numbers. Those with 0 to 8 years of education were less likely to name the current president and correctly answer the serial-threes item than those with 12 or more years of education. Those aged 80 or older were less likely to correctly identify the day of the week than those aged 60 to 69. Future studies seeking to develop new cognitive screening measures should perform DIF analyses in the instrument development phase to eliminate DIF items a priori. © 2005 Sage Publications.