Are measurements of patient safety culture and adverse events valid and reliable? Results from a cross sectional study

Background: The association between measurements of the patient safety culture and the true patient safety has been insufficiently documented, and the validity of the tools used for the measurements has been questioned. This study explored associations between the patient safety culture and adverse events, and evaluated the validity of the tools. Methods: In 2008/2009, a survey on patient safety culture was performed with Hospital Survey on Patient Safety Culture (HSOPSC) in two medical departments in two geographically separated hospitals of Innlandet Hospital Trust. Later, a retrospective analysis of adverse events during the same period was performed with the Global Trigger Tool (GTT). The safety culture and adverse events were compared between the departments. Results: 185 employees participated in the study, and 272 patient records were analysed. The HSOPSC scores were lower and adverse events less prevalent in department 1 than in department 2. In departments 1 and 2 the mean HSOPSC scores (SD) were at the unit level 3.62 (0.42) and 3.90 (0.37) (p < 0.001), and at the hospital level 3.35 (1.53) and 3.67 (0.53) (ns, p = 0.19) respectively. The proportion of records with adverse events were 10/135 (7%) and 28/137 (20%) (p = 0.003) respectively. Conclusions: There was an inverse association between the patient safety culture and adverse events. Until the criterion validity of the tools for measuring patient safety culture and tracking of adverse events have been further evaluated, measurement of patient safety culture could not be used as a proxy for the true safety.