Hazards of blind analysis of neuropsychological test data in assessing cognitive disability: the role of confounding factors

Neuropsychological testing has frequently been perceived by many health care and rehabilitation professionals as simply the administration and scoring of standardized neuropsychological tests followed by a comparison of the patient's scores to normative standards for the purposes of determining the patient's cognitive strengths and deficits, and whether or not the patient has sustained brain damage. Unfortunately, this simplistic model often results in inaccurate and misleading assessments of the patient's cognitive and behavioral functioning, erroneous diagnoses, and improper treatment. The issue of whether or not a patient has actually sustained a traumatic brain injury, or what specific cognitive and behavioral functions are impaired and to what degree, particularly in reference to a specific accident or event, cannot be determined solely by examining the patient's test data. Such data are frequently confounded by numerous factors which necessitate that the neuropsychologist proceed with caution and avoid arriving at any diagnostic impressions without a full appreciation of the impact of these factors, which may contribute significantly to the patient's neuropsychological test performance. This paper examines numerous potential confounds to test performance and discusses how the neuropsychologist can utilize a vector analysis approach to address the issue of the ecological validity of the neuropsychological test data.