Institutionally Based ImPACT Test® Normative Values May Differ from Manufacturer-Provided Normative Values

Abstract

Objective: The necessity for pre-injury baseline computerized neurocognitive assessments versus comparing post-concussion outcomes to manufacturer-provided normative data is unclear. Manufacturer-provided norms may not be equivalent to institution-specific norms, which poses risks for misclassifying the presence of impairment when comparing individual post-concussion performance to manufacturer-provided norms. The objective of this cohort study was to compare institutionally derived normative data to manufacturer-provided normative values provided by ImPACT® Applications, Incorporated.

Method: National Collegiate Athletic Association Division 1 university student athletes (n = 952; aged 19.2 ± 1.4 years, 42.5% female) from one university participated in this study by completing pre-injury baseline Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) assessments. Participants were separated into 4 groups based on ImPACT's age and gender norms: males <18 years old (n = 186), females <18 years old (n = 165), males >19 years old (n = 361) or females >19 years old (n = 240). Comparisons were made between manufacturer-provided norms and institutionally derived normative data for each of ImPACT's clinical composite scores: Verbal (VEM) and Visual (VIM) Memory, Visual Motor Speed (VMS), and Reaction Time (RT). Outcome scores were compared for all groups using a Chi-squared goodness of fit analysis.

Results: Institutionally derived normative data indicated above average performance for VEM, VIM, and VMS, and slightly below average performance for RT compared to the manufacturer-provided data (χ2 ≥ 20.867; p < 0.001).

Conclusions: Differences between manufacturer- and institution-based normative value distributions were observed. This has implications for an increased risk of misclassifying impairment following a concussion in lieu of comparison to baseline assessment and therefore supports the need to utilize baseline testing when feasible, or otherwise compare to institutionally derived norms rather than manufacturer-provided norms.

Keywords: Baseline testing; Concussion; Neuropsychological assessment; Normative data.