Measuring premorbid IQ in traumatic brain injury: An examination of the validity of the Wechsler Test of Adult Reading (WTAR)
- 22 January 2008
- journal article
- research article
- Published by Informa UK Limited in Journal of Clinical and Experimental Neuropsychology
- Vol. 30 (2), 163-172
- https://doi.org/10.1080/13803390701300524
Abstract
Estimation of premorbid IQ in traumatic brain injury (TBI) is clinically and scientifically valuable because it permits the quantification of the cognitive impact of injury. This is achieved by comparing performances on tests of current ability to estimates of premorbid IQ, thereby enabling current capacity to be interpreted in light of preinjury ability. However, the validity of premorbid IQ tests that are commonly used for TBI has been questioned. In the present study, we examined the psychometric properties of a recently developed test, the Wechsler Test of Adult Reading (WTAR), which has yet to be examined for TBI. The cognitive performance of a group of 24 patients recovering from TBI (with a mean Glasgow Coma Scale score in the severely impaired range) was measured at 2 and 5 months postinjury. On both occasions, patients were administered three tests that have been used to measure premorbid IQ (the WTAR and the Vocabulary and Matrix Reasoning subtests of the Wechsler Adult Intelligence Scale 3rd Edition, WAIS-III) and three tests of current ability (Symbol Digit Modalities Test–Oral and Similarities and Block Design subtests of the WAIS-III). We found that performance significantly improved on tests of current cognitive ability, confirming recovery. In contrast, stable performance was observed on the WTAR from Assessment 1 (M = 34.25/50) to Assessment 2 (M = 34.21/50; r = .970, p < .001). Mean improvement across assessments was negligible (t = −0.086, p = .47; Cohen's d = −0.005), and minimal individual participant change was observed (modal scaled score change = 0). WTAR scores were also highly similar to scores on a demographic estimate of premorbid IQ. Thus, converging evidence—high stability during recovery from TBI and similar IQ estimates to those of a demographic equation—suggests that the WTAR is a valid measure of premorbid IQ for TBI. Where word pronunciation tests are indicated (i.e., in patients for whom English is spoken and read fluently), these results endorse the use of the WTAR for patients with TBI.Keywords
This publication has 27 references indexed in Scilit:
- The Wasi Matrix Reasoning SubtestInternational Journal of Neuroscience, 2005
- Normative Data on a Measure of Estimated Premorbid Abilities as Part of a Dementia EvaluationApplied Neuropsychology, 1998
- estimating premorbid WAIS-R IQ with demographic variables: Regression equations derived from a UK sampleThe Clinical Neuropsychologist, 1997
- Neuropsychological assessment.Journal of Neurology, Neurosurgery & Psychiatry, 1995
- Does the NART hold after head injury?: A case reportBritish Journal of Clinical Psychology, 1991
- Evaluation of Wechsler Adult Intelligence Scale—Revised premorbid IQ formulas in clinical populations.Psychological Assessment, 1990
- Predicting premorbid IQ: A revision of the national adult reading testThe Clinical Neuropsychologist, 1989
- The WAIS—R index for estimating premorbid intelligence: Cross-validation and clinical utility.Journal of Consulting and Clinical Psychology, 1987
- The Galveston Orientation and Amnesia TestThe Journal of Nervous and Mental Disease, 1979
- Dementia: The Estimation of Premorbid Intelligence Levels Using the New Adult Reading TestCortex, 1978