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Measuring reliable change in traumatic brain injury (TBI): The pitfalls of using readily available formulae

Abstract Individuals with a traumatic brain injury (TBI) frequently undergo repeat neuropsychological assessments. Reliable change (RC) methodologies based on general population normative data are often used to assess for clinically significant change. The consequence of applying such methodologies to an individual with a TBI needs investigation. The current study tested the validity of readily available formulae in moderate to severe TBI participants who were >2 years postinjury. Participants were administered the Wechsler Adult Intelligence Scale-IV/Wechsler Memory Scale-IV (WAIS/WMS-IV) battery on two occasions across an approximate 1 year interval. Index scores were entered into 10 RC formulae to assess their validity in individuals with a TBI. Findings revealed that the formulae used in the study are relatively interchangeable in regards to WAIS-IV assessment, but that many of the formulae identified statistically unexpected rates of RC change in memory tasks assessed by the WMS-IV. Two formulae that did not contain statistical manipulations for practice effects performed relatively well in regards to memory assessment. Therefore, indiscriminate use of RC formulae could lead to over identifying memory decline in the TBI populations. The results suggest that either Iverson or Jacobson and Truax formulae can be used to assess RC for memory in moderate to severe TBI populations.