Preliminary study to evaluate the validity of the mini-mental state examination in a normal population in Turkey.

Although the Mini-Mental State Examination (MMSE) is widely used in clinical practice, normative scores for a healthy population have not been documented in Turkey. The aim in this study was to validate the MMSE in a healthy population and to provide normal scores. Internal construct validity of the Turkish version of MMSE among a preliminary sample of 406 normal people was assessed by Rasch unidimensional measurement model. Scores of the normal sample varied according to age and education but not according to sex. The data derived from this sample showed poor fit to the Rasch model (mean item fit, -2.082, SD 3.022). Only four of 11 items met model expectations. There was also differential item functioning by education and age for most items. Thus the internal construct validity of the Turkish MMSE in a normative sample could not be demonstrated by Rasch analysis. The scale failed modern psychometric criteria for scalability. We would therefore suggest other large normative MMSE data sets to be tested in terms of internal construct validity. If these findings are replicated, the validity of MMSE norms and their consequent use in clinical practice should be reconsidered.