Neuropsychological assessments are often done to determine if there has been a deterioration in a patient’s functioning due to, for example, dementia or a traumatic brain injury. The test scores are mostly meaningless, though, if the examiner does not have some indication or an estimate of how the person performed pre-morbidly. To illustrate, if a patient scores in the average range for most cognitive tests but used to function at a significantly higher level, then the average scores are significantly low. If you did not know that the patient had such high functioning pre-morbidly, then you might come to the wrong conclusion that his functioning has not deteriorated.
There are several ways to estimate pre-morbid functioning, and research has shown that certain tests are fairly resilient to brain insult (Lezak, 2012). There does not seem to be any research, though, into the validity of those tests in the South African population.
One of the methods of estimating pre-morbid functioning, is to test a patient’s vocabulary (Lezak, 2012). Since most of these tests (such as those found in the Wechsler IQ tests) are in English, this approach cannot be used with any confidence with the majority of South Africans whose first language is not English. Even with English first language speakers, level and quality of education is likely to interfere with the validity of such a method.
Research is needed into suitable measures of pre-morbid functioning for South Africans.
Please leave a reply/comment below, especially if you are thinking of doing this research.
Baddeley A, Emslie H, Nimmo-Smith I. The Spot-the-Word test: a robust estimate of verbal intelligence based on lexical decision. Br J Clin Psychol. 1993;32(1):55-65. doi:10.1111/j.2044-8260.1993.tb01027.x
Krull, K.R., Scott, J.G., & Sherer, M. (1995). Estimation of premorbid intelligence from combined performance and demographic variables. The Clinical Neuropsychologist, 9, 83 – 88.
Lezak, M.D., Howieson, D.B., Bigler, E.D., & Tranel, D. (2012). Neuropsychological Assessment. Oxford University Press: Oxford.
Vanderploeg, R.D. & Schinka, J.A. (1995). Predicting WAIS-R IQ premorbid ability: Combining subtest performance and demographic variable predictors. Archives of Clinical Neuropsychology, 10, 225 – 239.