Impact of repeated hospital accreditation surveys on quality and reliability, an 8-year interrupted time series analysis.

Objective: To evaluate whether hospital re-accreditation improves quality, patient safety and reliability over three accreditation cycles by testing the accreditation life cycle model on quality measures.

Design: The validity of the life cycle model was tested by calibrating interrupted time series (ITS) regression equations for 27 quality measures. The change in the variation of quality over the three accreditation cycles was evaluated using the Levene's test.

Setting: A 650-bed tertiary academic hospital in Abu Dhabi, UAE.

Participants: Each month (over 96 months), a simple random sample of 10% of patient records was selected and audited resulting in a total of 388 800 observations from 14 500 records.

Interventions: The impact of hospital accreditation on the 27 quality measures was observed for 96 months, 1-year preaccreditation (2007) and 3 years postaccreditation for each of the three accreditation cycles (2008, 2011 and 2014).

Main Outcome Measures: The life cycle model was evaluated by aggregating the data for 27 quality measures to produce a composite score (Y) and to fit an ITS regression equation to the unweighted monthly mean of the series.

Results: The results provide some evidence for the validity of the four phases of the life cycle namely, the initiation phase, the presurvey phase, the postaccreditation slump and the stagnation phase. Furthermore, the life cycle model explains 87% of the variation in quality compliance measures (R=0.87). The best-fit ITS model contains two significant variables (β and β) (p≤0.001). The Levene's test (p≤0.05) demonstrated a significant reduction in variation of the quality measures (Y) with subsequent accreditation cycles.

Conclusion: The study demonstrates that accreditation has the capacity to sustain improvements over the accreditation cycle. The significant reduction in the variation of the quality measures (Y) with subsequent accreditation cycles indicates that accreditation supports the goal of high reliability.