RT Journal Article SR Electronic T1 Crude versus case-mix-adjusted control charts for safety monitoring in thyroid surgery JF Quality and Safety in Health Care JO Qual Saf Health Care FD BMJ Publishing Group Ltd SP e17 OP e17 DO 10.1136/qshc.2008.031799 VO 19 IS 6 A1 Antoine Duclos A1 Nicolas Voirin A1 Sandrine Touzet A1 Pietro Soardo A1 Anne-Marie Schott A1 Cyrille Colin A1 Jean-Louis Peix A1 Jean-Christophe Lifante YR 2010 UL http://qualitysafety.bmj.com/content/19/6/e17.abstract AB Introduction Patient-safety monitoring based on health-outcome indicators can lead to misinterpretation of changes in case mix. This study aimed to compare the detection of indicator variations between crude and case-mix-adjusted control charts using data from thyroid surgeries.Methods The study population included each patient who underwent thyroid surgery in a teaching hospital from January 2006 to May 2008. Patient safety was monitored according to two indicators, which are immediately recognisable postoperative complications: recurrent laryngeal nerve palsy and hypocalcaemia. Each indicator was plotted monthly on a p-control chart using exact limits. The weighted κ statistic was calculated to measure the agreement between crude and case-mix-adjusted control charts.Results We evaluated the outcomes of 1405 thyroidectomies. The overall proportions of immediate recurrent laryngeal nerve palsy and hypocalcaemia were 7.4% and 20.5%, respectively. The proportion of agreement in the detection of indicator variations between the crude and case-mix-adjusted p-charts was 95% (95% CI 85% to 99%). The strength of the agreement was κ=0.76 (95% CI 0.54 to 0.98). The single special cause of variation that occurred was only detected by the case-mix-adjusted p-chart.Conclusions There was good agreement in the detection of indicator variations between crude and case-mix-adjusted p-charts. The joint use of crude and adjusted charts seems to be a reasonable approach to increase the accuracy of interpretation of variations in outcome indicators.