Prior to implementing the hospital standardised mortality ratio (HSMR) for hospital comparisons and improvement of quality of care, some adaptations need to be made. HSMR is a promising instrument, however, the current measurement is too distorted by factors other than quality of care. This conclusion was drawn by Wim van den Bosch in his thesis defended on November 2 2011 at the VUmc in Amsterdam, based on a study at Santeon and supervised at NIVEL.