Methods for additional analyses (e.g. subgroup analyses) {20b}
catheter-related dialysis dysfunction
SECONDARY, COMPLICATIONS, SENSITIVITY
As the sample size is not very large, there is a risk for imbalance in baseline characteristics between groups. This possible imbalance will be tested in a sensitivity test using univariate analyses. If needed, a comparison of the primary outcome between the groups will then be performed with a test where baseline characteristics can be stratified (e.g. the Cochran-Mantel–Haenszel test).The Wilcoxon rank-sum test will be used to examine if the time until the CT venography differs between the groups.Evaluation of the US/Doppler method will be made only in patients having undergone both an US/Doppler examination and CT venography. Sensitivity and specificity for the US-based method as compared to the golden standard, CT venography, will be determined and presented along with 95% confidence intervals. This will be performed for both intervention groups pooled together.For all other secondary outcomes (the patients’ experience of the catheterisation, catheter blood flow during dialysis, catheter-related dialysis dysfunction, mechanical complications), data are expressed as mean (SD) or median and range. Qualitative variables are expressed as frequency with percentage. The 