Abstract
BACKGROUND: Previous analyses of small-area appendicectomy rates showed significantly higher regional differences in the frequency of operations in women than in men OBJECTIVE: This work proposes valid measures to represent regional variations and analyzes gender-specific changes of appendicectomy rates at the county level in the time series. MATERIAL AND METHODS: Appendicectomy frequencies for 2014, 2016 and 2018 by gender and at the county level were taken from the DRG statistics. Regional variations were calculated and assessed using the systematic component of variation (SCV). In comparison to the extreme ratio and coefficient of variation, the SCV is more robust with respect to strongly fluctuating denominator populations. The SCV values greater than 5 indicate high variation and greater than 10 indicate very high variation. RESULTS: In the male population only minor regional variations in operation rates could be observed, remaining at similar levels over time (SCV(2014) = 2.1, SCV(2016) = 1.8, and SCV(2018) = 2.0). For women the SCV was above 5 in 2014 as well as in 2016 (SCV(2014) = 6.1, SCV(2016) = 5.3) and dropped to 4.5 in 2018. Plots as a funnel plot account for higher scatter in surgery rates in counties with low populations. DISCUSSION: Regarding women, a decreasing trend in regional variation of appendicectomy could be observed. It remains unclear whether this trend reflects a change in the indications or a modified clinical management when appendicitis is suspected. Using robust variation measures and the graphic preparation as funnel plots it is possible to distinguish systematically caused regional differences in care from random effects.