Abstract: In the initial review, we included one ITS study that evaluated a targeted educational intervention aimed at reducing the incidence of wrong-site tooth extractions. The intervention included examination of previous cases of wrong-site tooth extractions, educational intervention including a presentation of cases of erroneous extractions, explanation of relevant clinical guidelines and feedback by an instructor. Data were reported from all patients on the surveillance system of a University Medical centre in Taiwan with a total of 24,406 tooth extractions before the intervention and 28,084 tooth extractions after the intervention. We re-analysed the data using the Prais-Winsten time series and the change in level for annual number of mishaps was statistically significant at -4.52 (95% confidence interval (CI) -6.83 to -2.217) (standard error (SE) 0.5380). The change in slope was statistically significant at -1.16 (95% CI -2.22 to -0.10) (SE 0.2472; P < 0.05). This update includes an additional study reporting on the incidence of neurological WSS at a university hospital both before and after the Universal Protocol’s implementation. A total of 22,743 patients undergoing neurosurgical procedures at the University of Illionois College of Medicine at Peoria, Illinois, United States of America were reported. Of these, 7286 patients were reported before the intervention and 15,456 patients were reported after the intervention. The authors found a significant difference (P < 0.001) in the incidence of WSS between the before period, 1999 to 2004, and the after period, 2005 to 2011.  Similarly, data were re-analysed using Prais-Winsten regression to correct for autocorrelation. As the incidences were reported by year only and the intervention occurred in July 2004, the intervention year 2004 was excluded from the analysis. The change in level at the point the intervention was introduced was not statistically significant at -0.078 percentage points (pp) (95% CI -0.176 pp to 0.02 pp; SE 0.042; P = 0.103). The change in slope was statistically significant at 0.031 (95% CI 0.004 to 0.058; SE 0.012; P < 0.05). The findings of this update added one additional ITS study to the previous review which contained one ITS study. The original review suggested that the use of a specific educational intervention in the context of a dental outpatient setting, which targets junior dental staff using a training session that included cases of wrong-site surgery, presentation of clinical guidelines and feedback by an instructor, was associated with a reduction in the incidence of wrong-site tooth extractions. The additional study in this update evaluated the annual incidence rates of wrong-site surgery in a neurosurgical population before and after the implementation of the Universal Protocol. The data suggested a strong downward trend in the incidence of wrong-site surgery prior to the intervention with the incidence rate approaching zero. The effect of the intervention in these studies however remains unclear, as data reflect only two small low-quality studies in very specific population groups.

Plain-language summary: This updated review contains two interrupted-time-series (ITS) studies (studies in which data are collected at multiple time points before and after an intervention), one from the original review, which evaluated a targeted educational intervention aimed at reducing the incidence of wrong-site surgery, and which was found to reduce its incidence. An additional study evaluated the incidence of wrong-site surgery before and after the introduction of the Universal Protocol, however the relevance of these findings regarding the impact of the intervention is unclear given that prior to its introduction, the incidence was decreasing due to other unclear factors. Overall, this review now contains two studies, of relatively low quality evidence, on very specific populations and their generalisability to a larger audience is low.