Children in the United Kingdom with congenital heart disease undergo surgery and catheter based interventions with a very high probability of survival as counted at 30 days and one year, according to data from the United Kingdom's central cardiac audit database.1 The publication of these excellent results concerning a high profile area of practice prompts a reflection on the issues surrounding the collection and validation of clinical data and the methods used to evaluate outcomes.

To keep a tally of operations and their outcome, to have these results available for reflection, to be shared with colleagues, and for inspection by others, should be a simple matter and entirely appropriate.2 Compared with, for example, the long term, multiple, and relatively subjective outcomes of cleft lip and palate correction, cardiac surgery is a readily countable activity—each operation is a major event, and death is an absolute and objective outcome. But doing this well has proved to be very difficult. When an audit was conducted in adult surgery of all cases operated on between April 1997 and March 1998 in 10 UK centres, 25% of essential data elements were missing.3 In this central cardiac audit database report 22% of deaths would have been …