Comparison of the WRAT4 reading subtest and the WTAR for estimating premorbid ability level

The need to estimate premorbid ability level as part of a neuropsychological evaluation is well understood in the profession. The purpose of this study was to evaluate two popular reading tests for estimating premorbid ability. Participants were 102 undergraduate volunteers between the ages of 18 and 64 years (M = 25.89 years, SD = 9.54). Participants completed the Wechsler Test of Adult Reading (WTAR) and both forms of the Reading subtest of the Wide Range Achievement Test-Fourth Edition (WRAT4). The WTAR was scored using the Predicted Full-Scale IQ (FSIQ) and the Demographic Predicted FSIQ methods presented in the manual. Repeated-measures analyses of variance revealed no significant difference between the two forms of the WRAT4 and the WTAR for both the Predicted FSIQ, F(2, 202) = 0.399, p = .671, and the Demographic Predicted FSIQ, F(2, 190) = 0.085, p = .918, scoring approaches. Concurrent validity correlation coefficients between the three items using the Predicted FSIQ ranged from r = .75 to r = .78; using the Demographic Predicted FSIQ, coefficients ranged from r = .50 to r = .76. Our data suggest that the WTAR offers a slightly more reliable statistical portrait of cognitive functioning, especially with a more educated and originally higher-functioning population.