Understanding the risk-adjusted mortality ratio
Risk adjustment (or case-mix adjustment) takes into account patient risk factors to calculate a predicted mortality ratio. This means that hospitals or consultants who see higher risk patients have their mortality rate adjusted to account for the factors that put these patients at greater risk.
Understanding the 'funnel plot'
The funnel plot displays the risk-adjusted elective procedural mortality ratio for each hospital, plotted against the expected number of mortalities for that hospital. The expected number of mortality events for each hospital will vary, dependent upon the number of procedures that have been performed and the risk profile of the patients they have been treated. The horizontal grey line represents the national average mortality ratio and the coloured lines the upper and lower 95% and 99.8% control limits. If a plot is above the upper 99.8% (blue) control line, the data is suggesting that the mortality ratio is higher than expected. Where plots are between that upper control limit and the lower control limit (yellow line), the mortality ratio is within the expected range. The hospital’s position is represented by the magenta-coloured plot.
