[Funnel plots for comparing pressure ulcer and fall rates in 76 nursing homes]

The aim of this study was to display the values of the quality indicators "falls in the institution" and "institutionally acquired pressure ulcers" of 76 German nursing homes in bar graphs and funnel plots and to discuss the advantages and disadvantages of both methods.

In 2009 a nationwide prevalence study has been conducted in 76 nursing homes (n= 5 521). Among others two trained data collectors assessed the fall and pressure ulcer risks, the presence of pressure ulcers and whether nursing home residents fell. Risk adjusted fall and pressure ulcer prevalence rates were calculated per institution and displayed in bar graphs and funnel plots.

The proportions of residents with pressure ulcers grade 2, 3 or 4 varied between 0 and 11%. The average pressure ulcer prevalence was 2.5%. On average, 6% of residents at risk for falling fell during the last 2 weeks. The proportions of fallen residents varied between 0% and 100%. In bar graphs differences between institutions and rankings can be displayed. However, the precision of the point estimates is not taken into account. Furthermore, criteria for determining conspicuous institutions are arbitrary. In funnel plots values are plotted against their precision. Although there were differences between the investigated nursing homes, most of them could be explained by chance.

Funnel plots should be used when comparing medical or nursing performance between health care institutions. They take the precision of estimates into account that is usually the size of the institution. Despite differences, there was no nursing home with a prevalence of institutionally acquired pressure ulcers that was significantly higher than those in all the other institutions. In 2 out of 75 nursing homes the proportions of fallers were higher than expected by chance. In terms of performance improvement the reasons for this should be further investigated. However, in spite of the advantages of funnel plots they do not provide guidance as to whether the measured results can be tolerated and are acceptable.