The Incidence of 30-Day Adverse Events After Colonoscopy Among Outpatients in the Netherlands

Vincent de Jonge, BSc; Jerome Sint Nicolaas, BSc; Onno van Baalen, MD; Johannes T. Brouwer MD, PhD; Mark F.J. Stolk, MD, PhD; Thjon J. Tang, MD, PhD; Antonie J.P. van Tilburg, MD, PhD; Monique E. van Leerdam, MD, PhD; Ernst J. Kuipers MD, PhD


Am J Gastroenterol. 2012;107(6):878-884. 

In This Article


This study took place in the context of a quality evaluation of colonoscopy performance in the Netherlands in 12 hospitals. Ethical approval for the study was obtained from the Institutional Review Board in each individual hospital. Consecutive outpatients undergoing a colonoscopy in one of 12 participating centers were asked to complete a patient satisfaction survey about their experiences during the whole endoscopy journey. A total of 150 surveys were required per department to complete the study. The survey consisted of a pre- and post-procedure questionnaire. At the end of the pre-procedure part (completed in the waiting room before the colonoscopy), patients were asked for permission to be called 30 days after the procedure.

Patients were contacted for this adverse event registration study between January 2010 and September 2010. A standard telephone interview was developed based on the most common adverse events reported in the literature (Figure 1).[11] The standard interview first asked about general health problems in the 30 days after the procedure. Next, the occurrence of gastrointestinal symptoms was assessed, with specific interest in bleeding and abdominal discomfort. We further assessed the severity and duration of bleeding and abdominal discomfort on a 3-point scale. It was also assessed whether patients had visited their family physician, an emergency department, or hospital. At last, it was assessed how many days of work (if applicable) were lost as a consequence of the procedure, excluding the day of the procedure.

Figure 1.

Standard telephone interview assessing the incidence of adverse events in the 30 days after colonoscopy.

The target of the adverse event registration study was to include at least 1,000 patients. Three researchers called the individuals 30 days after their procedure. Individuals were called at the end of the day or beginning of the evening on working days. When a subject could not be reached, they were approached again several days later. After two attempts, the subject was noticed to be not reached by telephone.

At the end of the study, the related colonoscopy reports were identified in the hospital files and the following data were recorded: date of birth, gender, indication for endoscopy, use of sedation, quality of bowel preparation, therapeutic interventions during the procedure, extent of the procedure, endoscopic findings, and definite adverse events. Additionally, the telephone interview was linked to the satisfaction survey. Six months after the study end, the hospital records of all patients were checked to see whether patients were deceased during the study period.

For data analyses, a distinction was made between major adverse events and minor adverse events. Major adverse events were defined as any health problem that made the patient visit an emergency department or hospital within the 30 days after their colonoscopy. Minor adverse events were defined as any health problem that the patient experienced in the 30 days after the procedure, not requiring a hospital visit. Individual patients could report both major and minor adverse events. When complaints had already existed before the procedure (based on the indication provided in the report, the patient satisfaction survey, or the telephone interview), similar complaints in the 30 days after the procedure were not regarded as an adverse event, unless it was specifically stated that the complaints had deteriorated after the colonoscopy. Both major and minor adverse events were further divided in definite-related, possible-related, and unrelated adverse events. The hospital record was searched to assess the relation between major adverse events and the colonoscopy, time between the colonoscopy and the adverse were also taken into account. For minor adverse events, two investigators discussed and reached consensus whether the event had been definite-, possible-, or unrelated.

Statistical analyses were performed using the SPSS statistical package, version 17.0 (IBM Corporation, Chicago, IL). Descriptive statistics were performed using χ2 tests (categorical data) and Student's t-test (continuous data). Multivariate binary logistic regression using robust standard errors was performed to find predictors of the occurrence of any (major or minor) definite-related adverse event. The following variables were included in the model: gender, age, screening/surveillance as indication, the use of sedation, polypectomy, and specialism of the endoscopist. A two-sided P value of <0.05 was considered to be significant.


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