were built into the questionnaire. Hospitals received a detailed report on their data and the overall results. Statistical analysis All data were checked for completeness prior to statistical analysis. Confidence intervals were calculated with the Wilson score. All descriptive analyses were conducted using Excel and SAS 9.1. RESULTS Participation In total, 92 surveys were conducted (Figure1) by 41 different hospitals – representing 43% of all the hospitals in The Netherlands. The number of surveys conducted for each hospital was as follows: 10 institutions participated once, 20 participated twice, two participated three times and nine, four times. Figure1 also shows the distribution of hospital size, based on the average number per period: 32% of the hospitals had ≤200patients, 51% 200–400 and 17% >400. Six of the eight Dutch university medical centres participated. The consecutive numbers of patients included per period were 8424, 3497, 9449 and 5567. Figure 1: Prevalence of infections per period (lled diamonds), with 95% condence interval [ ≤200 patients per survey (dark grey bars), 200–400 patients per survey (mid‐grey bars) and >400 patients per survey (light grey bars)]. 94 Chapter 5
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