Reliability of instruments in a cooperative, multisite study: employment intervention demonstration program.

Reliability of well-known instruments was examined in 202 people with severe mental illness participating in a multisite vocational study. We examined interrater reliability of the Positive and Negative Syndrome Scale (PANSS) and the internal consistency and test-retest reliability of the PANSS, the Rosenberg Self-Esteem Scale, the Medical Outcomes Study Short Form-36 (SF-36), and the Quality of Life Interview. Most scales had good levels of reliability, with intraclass correlation coefficients (ICCs) and coefficient alphas above .70. However, the SF-36 scales were generally less stable over time, particularly Social Functioning (ICC = .55). Test-retest reliability was lower among less educated respondents and among ethnic minorities. We recommend close monitoring of psychometric issues in future multisite studies.