Comparing Methods for Estimating Premorbid Intellectual Functioning

Efforts to determine premorbid intellectual functioning for a patient prior to their current evaluation has been attempted using demographic information, current performance data, or a combination of both. Five of these premorbid intellectual prediction methods were assessed in a sample of 104 neurological patients referred for neuropsychological evaluation and a matched control sample. Predicted Full-Scale Intelligence Quotient (FSIQ) scores of patients did not differ from the true FSIQ scores of the matched controls. Logistic regression analyses found no difference in classification accuracy among the prediction methods. The findings of this study found combined demographic and performance methods developed by Vanderploeg and Schinka (1995), Vanderploeg, Schinka, and Axelrod (1996), Krull, Scott, and Sherer (1995) and Williamson, Krull, and Scott (1996) to be accurate estimates of premorbid functioning. This study found estimates of premorbid functioning based on demographic data alone (Barona, Reynolds, & Chastain, 1984) not to differ from the other methods, which is at odds with prior studies. Prospective studies employing all of these methods are recommended to clarify the utility of demographically based estimates.