Methods of estimating premorbid functioning

Clinical neuropsychological assessment frequently requires the comparison of obtained scores against some estimate of premorbid level of functioning, but only recently has significant attention been turned to objective methods to accomplish this objective. Clinical judgment, although useful in some circumstances, is generally insufficient. Other methods of estimating premorbid function include demographic regression formulae, such as the Barona formula, subtest scatter methods, such as that suggested by Lezak, and the use of current scores on tests of presumably spared abilities, such as the National Adult Reading Test (NART). Almost all methods predict to some general level of intellectual functioning rather than to specific neuropsychological skills. This paper reviews the suggested methods in terms of the underlying assumptions and the available empirical evidence. Suggestions for future research include the development of skill specific predictors as well as investigations regarding the relation between predictor accuracy and characteristics of the subject, such as high versus low premorbid functioning in the subject. Additionally, there is a great need for methods to predict premorbid functioning in children.