Validity and reliability of the Johns Hopkins Adapted Cognitive Exam for critically ill patients

Abstract

OBJECTIVE:To validate The Johns Hopkins Adapted Cognitive Exam designed to assess and quantify cognition in critically ill patients.DESIGN:Prospective cohort study.SETTING:Neurosciences, surgical, and medical intensive care units at The Johns Hopkins Hospital.PATIENTS:One hundred six adult critically ill patients.INTERVENTIONS:One expert neurologic assessment and four measurements of the Adapted Cognitive Exam (all patients). Four measurements of the Folstein Mini-Mental State Examination in nonintubated patients only. Adapted Cognitive Exam and Mini-Mental State Examination were performed by 76 different raters.MEASUREMENTS AND MAIN RESULTS:One hundred six patients were assessed, 46 intubated and 60 nonintubated, resulting in 424 Adapted Cognitive Exam and 240 Mini-Mental State Examination measurements. Criterion validity was assessed by comparing Adapted Cognitive Exam with a neurointensivist's assessment of cognitive status (ρ = 0.83, p < .001). Ordinal logistic regression established optimal predicted cut points for cognitive status classification (≤ 28 = severely impaired, 29-55 = moderately impaired, ≥ 56 = mildly impaired or normal). Using these cut points, the Adapted Cognitive Exam appropriately classified cognitive status 90% of the time. Construct validity was assessed by comparing Adapted Cognitive Exam with Mini-Mental State Examination in nonintubated patients (ρ = 0.81, p < .001). Face validity was assessed by surveying raters who used both the Adapted Cognitive Exam and Mini-Mental State Examination and indicated the Adapted Cognitive Exam was an accurate reflection of the patient's cognitive status, more sensitive a marker of cognition than the Mini-Mental State Examination, and easy to use. The Adapted Cognitive Exam demonstrated excellent interrater reliability (intraclass correlation coefficient = 0.997; 95% confidence interval 0.997-0.998) and interitem reliability of each of the five subscales of the Adapted Cognitive Exam and Mini-Mental State Examination (Cronbach's α: range for Adapted Cognitive Exam = 0.83-0.88; range for Mini-Mental State Examination = 0.72-0.81).CONCLUSION:The Adapted Cognitive Exam is the first valid and reliable examination for the assessment and quantification of cognition in critically ill patients. It provides a useful, objective tool that can be used by any member of the interdisciplinary critical care team to support clinical assessment and research efforts.