{'fraction_non_alphanumeric': 0.016660758596242466, 'fraction_numerical': 0.0014179369018078695, 'mean_word_length': 5.767386091127098, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Current challenges for outcome measurement in surgical practice.

The outcome of surgery, the effect of the intervention on patient health and wellbeing, is the greatest concem for patients and a major criterion for measuring the effectiveness of surgical care. The systematic assessment of clinical practice encompasses outcomes which are of relevance to patients-mortality, morbidity, complications ofthe procedure, symptom reduction, change in functional status and quality of life-as well as the traditional physiological, biological and radiological indicators. Recent outcomes research has highlighted the importance of multidisciplinary collaboration by surgeons with specialists from disciplines such as epidemiology, statistics, health economics, medical sociology and health psychology in order to devise new strategies and methods for making inferences from experimental and nonexperimental surgical studies. This has been welcomed by professionals and policy makers who are concerned about variation in practice and evidence regarding the appropriate use of surgical procedures (1). Initiatives such as the Health Technology Assessment Programme of the NHS Research and Development Directorate have highlighted the importance of measurements of the effectiveness, costs, the broader impact of procedures and the importance of practice being guided by quality outcomes evidence (1). In order to measure the outcome of surgical care it is first necessary to define the objectives of the intervention and to select a relevant outcome. Information concerning the outcome measure (eg postoperative myocardial infarction) should be related both to surgical activity and the underlying risk of this outcome in the study population. Most routine health services data provide only aggregate information recording the frequency of outcome events with no information linked to risk and the use of surgical services; as such they should not unequivocally be interpreted as indicators of surgical outcome (2). Nevertheless, for certain conditions, for example mortality due to cholecystectomy and appendicectomy, it has been argued that outcome indicators based on aggregate mortality rates may be of practical use because effective services should influence the value of the indicator (3). Interpretation of these indicators has, however, been confounded both by the small number of interventionrelated deaths which occur at a hospital or district level and the possible misclassification when coexisting diseases contribute to the mortality. The principal challenges which currently face those studying the outcome of surgical care relate to the choice of measure employed, the choice of study design and, in interpreting results, the case-mix of the participating patients. Each of these factors will now be considered.