The measurement and diagnostic utility of intrasubtest scatter in pediatric neuropsychology.

Intrasubtest scatter (ISS) is a measure of person's tendency toward inconsistency when responding to test items. It has been claimed that ISS may be suggestive of intellectual inefficiency, difficulty with recall of specific information, or fluctuating levels of arousal/attention. The research investigating these claims has been inconclusive, possibly because traditional indices of ISS may not adequately measure inconsistent responding. Item Response Theory (IRT) approaches to the detection of unusual response sequences appear to have a much firmer psychometric foundation but have been largely ignored in the neurodiagnostic literature. This study compares the utility of traditional and IRT-based indices of ISS in identifying children known to be experiencing information-processing difficulties. The WISC-R item responses of 100 children who have received cranial irradiation treatment for leukemia are compared with those of 100 healthy children. Results confirm the diagnostic utility of an IRT-based measure of unusual test behavior in this clinical group.