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J Patient Saf. 2018 Jun 11. doi: 10.1097/PTS.0000000000000504. [Epub ahead of print]

Psychometric Analysis of a Survey on Patient Safety Culture-Based Tool for Emergency Medical Services.

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Center for Patient Safety, Jefferson City, Missouri.
St. Louis Fire Department, St. Louis, Missouri.



Evaluating organizational safety culture is critical for high-stress, high-risk professions such as prehospital emergency medical services (EMS). The aim of the study was to evaluate the psychometric properties of a safety culture instrument for EMS, based on the Agency for Healthcare Research and Quality's widely used Surveys on Patient Safety Culture (SOPS).


The final EMS-adapted instrument consisted of 37 items covering 11 safety culture domains including 10 domains from existing SOPS instruments and one new domain for communication while en route to an emergency call. The analysis sample included 23,029 nationally certified EMS providers. Domain structure was evaluated on two separate halves of the data set through confirmatory factor analysis using a polychoric correlation matrix for ordinal data. The reliability and validity of each domain were evaluated using Cronbach α and Pearson correlation coefficients.


The confirmatory factor analysis supported the 11-domain model. All items loaded above the 0.4 threshold (range = 0.508-0.984). Three composite domains exhibited factor variance below the 0.5 threshold: staffing (0.32), communication about incidents (0.26), and handoffs (0.26). Floor and ceiling effects were not detected. Inter-item consistency exceeded 0.6 for all subscales (α = 0.65-0.88). Predictive validity was supported as all domain composites were correlated with the outcome variables of overall safety rating (r = 0.44-0.72) and frequency of event reporting (r = 0.31-0.48).


Overall, the EMS-adapted tool demonstrated adequate psychometric properties consistent with those of existing SOPS instruments. Additional research is needed to evaluate the instrument's performance at the agency level and its correlation with safety outcomes in the prehospital setting.

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