2.3 | Statistics
Statistical analyses were carried out using the software (SPSS v.25.0 package, IBM, Chicago, IL). Values of p ≤ 0.05 were considered significant. Categorical variables were documented as number and the corresponding percentage in brackets. For comparisons, the chi-squared test was employed. If the expected values in one group was < 5, Fisher’s exact test was performed. Metric demographic‬, clinical, and serological data were checked for normal distribution using the Kolmogorov-Smirnov test and the Shapiro-Wilk test. As none of the metric values were normally distributed, they were plotted as median and 25th/75th percentiles. For statistical evaluation, the Mann-Whitney U test was used. For survival evaluation Kaplan-Meier analyses with log-rank test were applied. Hazard ratios were calculated with Cox regression.
The investigations were carried out in accordance with the ethical guidelines of the “Declaration of Helsinki” and its amendment in “Tokyo and Venice”. The study was approved by the ethics committee of the Martin-Luther University Halle-Wittenberg. Informed written consent was obtained from each patient. Before the start of the investigation the study was registered in the German Clinical Trial Register under the number “DRKS00015776”.