Mental health programs need an instrument to monitor adherence to evidence-based physical health care for people with serious mental illness. The paper describes the Physical Health Care Fidelity Scale and study interrater reliability, frequency distribution, sensitivity to change and feasibility. Four fidelity assessments were conducted over 18 months at 13 sites randomized to implementation support for evidence-based physical health care. We found good to excellent interrater reliability, adequate sensitivity for change, good feasibility and wide variability in fidelity across sites after 18 months of implementation. Programs were more successful in establishing Policies stating physical health care standards than in implementing these Policies. The Physical Health Care Fidelity Scale measures and guides implementation of evidence-based physical health care reliably.Trial registration: ClinicalTrials.gov Identifier: NCT03271242.
Keywords: Evidence-based practice; Fidelity scale; Implementation; Physical health care; Psychoses.