Methods: A retrospective, observational multicentre study included 1964 patients (58 % male sex) with a
complicated urinary tract infection treated at Internal Medicine and Urology departments of 19 Dutch university and
non-university hospitals. Data of 50 patients per department were extracted from medical charts. QI performance scores
were calculated using previously constructed algorithms. Department and hospital characteristics were collected using
questionnaires filled in by an internal medicine physician and an urologist. Regression analysis was performed to identify
determinants of QI performance. Clustering at department and hospital level was taken into account through inclusion
of random effects in a multi-level model.