WS18.2 Using funnel plots to make meaningful centre comparisons

Abstract

Objectives The UK CF Registry annual reports include comparisons between centres on key outcomes such as FEV 1 using rankings. While illustrating the distribution between centres, they promote the assumption that those with the highest measures provide better care. We hypothesised a more scientific approach based on statistical process control and adjustment for case-mix may identify exceptional CF care services in terms of clinically meaningful outcomes. Methods We extracted FEV 1 and BMI on patients aged 12–21 from annual review data (2007–2012). Funnel plots were generated with confidence limits at 2 and 3 standard deviations (SD). Centres with mean values outside these limits are said to display cause – variability outside what one would expect. Outcomes were then adjusted for case mix (including gender, genotype, pancreatic sufficiency and socio-economic deprivation) and analysed using funnel plots. Results Using a primary outcome of FEV 1 at age 15, data for 1066 patients from 31 paediatric centres were available. Funnel plots of unadjusted data showed 8 centres with evidence of special cause variation (at 2SD limits). Initial adjustment for case-mix reduced the number of centres outside these limits to 3. None of the centres were outside the 3SD limits in either analysis. Similar patterns were found for BMI percentile in this age group. Conclusion In conclusion the work to-date illustrates that funnel plots can be used to identify differences in FEV 1 and BMI between specialist paediatric centres. Case-mix adjustment models should develop into a useful tool for making centre comparisons which can continue to be used by stakeholders.