Reliability and validity of prehospital case finding for depression and cognitive impairment.

OBJECTIVES To evaluate the test-retest reliability, the concurrent criterion validity, and the construct validity of prehospital, emergency medical service (EMS) case finding for depression and cognitive impairment in older adults. DESIGN Cross-sectional study. SETTING Prehospital EMS system and hospital emergency department. PARTICIPANTS EMS providers and community-dwelling older adult (aged > or =60) patients. INTERVENTIONS Case finding instruments for depression (Patient Health Questionnaire-2; PHQ-2) and cognitive impairment (Six-Item Screener). MEASUREMENTS The reliability and validity of these instruments. RESULTS Moderate test-retest reliability was found for prehospital application of the PHQ-2 (kappa=0.50) and Six-Item Screener (kappa=0.52), fair concurrent criterion validity for depression (kappa=0.36), and slight to fair concurrent criterion validity for cognitive impairment (kappa=0.11-0.23). Construct validity was demonstrated using the Multitrait-Multimethod Matrix. CONCLUSION Moderate test-retest reliability and construct validity were demonstrated for prehospital case finding by EMS providers for cognitive impairment and depression using these instruments. Slight to fair concurrent criterion validity was found, a result that methodological limitations could explain. These findings provide additional support for the concept of using EMS providers to detect older adults at risk for these conditions. Further work is needed to confirm the validity and effectiveness of prehospital screening before such programs are implemented.