Developing a regression equation for predicting premorbid functioning in an Australian sample using the National Adult Reading Test

ObjectiveIn neuropsychological assessment, predicting the level of premorbid functioning is useful in ascertaining the presence or absence of cognitive decline post-injury. This study set out to develop regression equations using the National Adult Reading Test (NART) in association with demographic factors to predict the Wechsler Adult Intelligence ScaleFourth Edition (WAIS-IV) full-scale intelligence quotient (FSIQ) and its index scores in a cognitively healthy Australian sample, and to compare the accuracy of these regression equation with the Test of Premorbid Functioning (TOPF) in a clinical sample. MethodThe 111 cognitively healthy male and female participants aged 18-65years completed a battery of tests, including the WAIS-IV, NART, and TOPF. The accuracy of the premorbid IQ estimates was then examined on 22 neurologically impaired participants. ResultsThe regression equation using NART errors explained 39.1% of the variance in WAIS-IV FSIQ. When age, sex, and education were added to the model, the variance increased to 46.6%. Both the regression equations using NART errors and the TOPF significantly over-estimated IQ in the clinical sample (p<.001), whereas the regression equation combining errors and demographics, and the TOPF with demographic correction, did not. ConclusionEstimating premorbid functioning is an important aspect of neuropsychological assessment. This paper developed a series of regression equations using the NART which are suitable for the Australian context.