Numerical and linear regression models were computed to analyse the impact of the investigated parameters on VOH. The relationship between a variable and a numerical end-point was measured with a Spearman correlation coefficient and a correlation test. In the case of a binary variable the end-point was transformed into a categorical variable that separates the values below and above the median. Odds Ratios OR and 95% Confidence Intervals (95%CI) were calculated to analyse the resulting 2x2 contingency table. All statistical tests were performed with R 3.2.2 (R Project for Statistical Computing, Vienna, Austria) by a senior bio-statistician.