Investigating the test of premorbid functioning (TOPF) in predicting Wechsler Abbreviated Scale of Intelligence - Second edition (WASI-II) scores in an Australian sample

Accurate prediction of premorbid functioning is important in neuropsychological assessment. We aimed to investigate the predictive accuracy of the TOPF and examine this word list at an item level against WASI-II scores, using Australian pronunciations. The sample of 219 healthy Australians were aged 18-82 years. Multiple regression analyses were used to replicate the TOPF and simple demographic models based on the US TOPF standardization. Rasch analyses provided a comparison of Australian, US and UK word order from the proportion of words pronounced correctly. The variance explained in WASI-II index scores ranged from R²=.12 (PRI) to .33 (FSIQ-2), which was approximately half that reported in the US standardization study. The accuracy of predicted WASI-II scores was also slightly less in our sample. Thirty-two words were out of place by five places or more compared with the US word order and 30 compared with the UK. These results add to concerns about the application the TOPF with norms developed in the US and UK in the Australian context. Clinicians are advised not to apply the five error discontinue rule when using the TOPF in the local context. Development of a more accurate word reading task for use in Australia is warranted.