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

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.