To determine the impact of increasing case finding of people with milder disease on the mortality trend within the UK CF registry from 2007 to 2010.
Why is this important?
Life expectancy and average survival of people with CF has been increasing year on year. Increasing numbers of people with milder disease are also being identified due to more wide-spread testing for CF. This has led to the suggestion that the impressive recent survival improvement is driven by widespread genetic testing identifying more people with milder disease.
What did you do?
We analysed the data between 2007 and 2011 from the UK CF registry. In particular, we compared the trend in average age at death for people with milder disease and people with ‘typical CF’. People with CF who are pancreatic insufficient (pancreas affected by CF) were considered to have ‘typical CF’ while people who are pancreatic sufficient were considered to have milder disease.
What did you find?
There was an increasing proportion of people with milder disease within the UK CF registry from 2007 to 2010. However, the improvement in survival for people with ‘typical CF’ is similar to the overall improvement in survival.
What does this mean and reasons for caution?
It is likely that the improvement in survival reported in the UK CF Registry from 2007 to 2010 represented the improvement in survival among people with ‘typical’ CF who are pancreatic insufficient. This suggests a true improvement in survival, rather than just an effect of including more people in the registry with more mild disease. Along with the findings of another study that the median age of death among people with CF is improving more rapidly than that of the general population, this should engender hope among the CF population. However, only data for four years were analysed and this analysis may be affected by the improvement of the data collection system.
Future analysis should be carried out, for example with 10-15 years’ worth of data, to ensure these results are reproducible.