Laurens Schattenkerk

154 Chapter 6 Statistical analysis Descriptive characteristics were reported as median with range in case of non-normally distributed variables or mean ± standard deviation (SD) in normally distributed variables. Comparison between groups was performed using chi-squared test for categorical data, Student’s T-test for parametric continuous data and the Mann-Whitney U test for nonparametric continuous data. CLABSI per 1000 days of duration of catheter stay was calculated using data from the first three inserted catheters. Lastly, a 1-Kaplan-Meier curve was composed with accompanying log-rank test to compare tunnelled versus non-tunnelled catheters in CLABSI occurrence. Multivariable logistic regression analysis was performed on the outcome of CLABSI occurrence of the first inserted central venous catheter. The assumption of linearity of the logit of ordinal variables was assessed using the Box-Tidwell test. Backward Wald selection was used for selection of variables using the standard p = 0.10 for variable removal. Assessment of confounding (increase in B-coefficient of >10%) and effect modification (significant interaction term). Significant risk factors were reported in odds ratio (OR) with 95% confidence intervals (95%-CI). Additionally, the adjusted R-squared is reported to show the proportion of the variance in the occurrence of CLABSI explained by the model. As part of a sensitivity analysis, a multivariate logistic regression analysis was repeated using only the CLABSIs that led to the removal of the central venous catheter as outcome variable. Chi-squared testing was used to analyse if there was a significant association between tunnelled or centrally inserted catheters and thrombosis. Results Patient and surgical characteristics In total 262 patients with intestinal atresia or gastroschisis were operated within the study period. In 22 patients there was no information on central venous catheter placement or removal and two patients were transferred to another hospital before catheter removal. Excluding these patients left a total of 238 patients. Baseline characteristics of these patients are displayed in Table 1. The type and location of the atresia in those treated for intestinal atresia and complex gastroschisis is provided in Table 2. Out of all patients 74% (N=175/238) were treated for intestinal atresia and 26% (N=63/238) for gastroschisis. Out of all gastroschisis patients, 22% (N=14/63) were treated for a complex gastroschisis which was 6% (N=14/238) of the overall cohort. Gastroschisis

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