Estimation of K-WAIS-IV Premorbid Intelligence in South Korea: Development of the KPIE-IV

The accurate estimation of premorbid intellectual functioning in patients with known or suspected cognitive impairment is crucial for clinicians. However, there is no reliable method for estimating premorbid intelligence in South Korea. The purpose of this study was to develop the Korea Premorbid Intelligence Estimate (KPIE) as an estimate of the premorbid intellectual functioning.Data from the Korean WAIS-IV standardization sample were used to generate several Full Scale Intelligence Quotient (FSIQ) estimation formulas using demographic variables and current WAIS-IV subtest performance. The standardization sample (N = 1216) was randomly divided into two groups: the first group was used to develop the formulas and the second group was used to validate the prediction equations. Age, education, gender, region of the country, and select subtest raw scores (Vocabulary, Information, Matrix Reasoning, and Visual Puzzle) were used as predictor variables.Five KPIE-4 equations were generated. Estimated FSIQ derived from the KPIE-4 equation is highly correlated with K-WAIS-IV FSIQ.The resulting formulas for estimating premorbid FSIQ were highly significant and precise in predicting FSIQ scores of participants in the K-WAIS-IV normative sample. These equations provide a means for clinicians to estimate intellectual functioning in adults, and can be utilized as a method of estimating individuals premorbid functioning.