BMJ  2005;330:43-44 (1 January), doi:10.1136/bmj.330.7481.43-c

Letter

Paediatric cardiac surgical mortality after Bristol

Paediatric cardiac hospital episode statistics are unreliable

EDITOR—The lack of accuracy of the hospital episode statistics used by Aylin et al to analyse the paediatric cardiac surgical mortality in England after Bristol is worrying.¹ Indeed, Aylin's group reported that hospital episode statistics "manifestly contain errors" and that their available data sources "have such clear limitations that one could ask whether any reliable conclusions can be drawn."² We have also shown hospital episode statistics data to be inaccurate for this complex specialty.³

This latest study raises more concerns about hospital episode statistics data, showing that errors are not consistent across the country.¹ A centre with a high proportion of outcome returns from hospital episode statistics (Oxford, for example) would almost inevitably identify more deaths than one with low returns, potentially giving a false impression of relative surgical performance.

The central cardiac audit database collects, validates, and analyses data from all UK paediatric cardiac units, centrally tracking mortality using direct links to the Office for National Statistics (where all deaths in England are registered). It started collecting data in 2000, so it does not have comprehensive data for comparison with all the epochs described by Aylin et al, but it has data on 2913 infants who had open heart operations in England during 2000-2.

Aylin et al report only 2607 infant operations in epoch 6 (1999-2002), which implies serious errors in their case ascertainment. They report an overall English perioperative mortality for infant open heart operations in epoch 6 of 4%, with 105 deaths identified over the three years. The central cardiac audit database has identified 185 deaths (7.8% mortality) in the cohort of 2385 open heart infant operations during 2000-2, its validated, centre specific mortality for all open heart infant operations in England for 2000-2 ranging between 3.3% and 10.7%. Two centres had higher mortality than Oxford, in contrast to Aylin et al's report. The 95% confidence intervals for difference in mortality between Oxford and all of England were - 4.1% to 8.7%, a large overlap, which means any difference is statistically insignificant.

jgibbs{at}boltblue.com Leeds General Infirmary, Leeds LS1 3EX

National Clinic Audit Support Programme, NHS Information Authority, Tavistock House, London WC1H 9JR

Great Ormond Street Hospital for Children, London WC1N 3JH

Southampton General Hospital, Southampton SO16 6YD

University College Hospital, London

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Competing interests: None declared.

References

1. Aylin P, Bottle A, Jarman B, Elliot P. Paediatric cardiac surgical mortality in England after Bristol: descriptive analysis of hospital episode statistics 1991-2002. BMJ 2004;329: 825-7. (9 October.)[Abstract/Free Full Text]
2. Aylin P, Alves B, Best N, Cook A, Elliott P, Evans SJ, et al. Comparison of UK paediatric cardiac surgical performance by analysis of routinely collected data 1984-1996: was Bristol an outlier? Lancet 2001;358: 181-7.[CrossRef][ISI][Medline]
3. Gibbs JL, Monro JL, Cunningham D, Rickards A. Survival after surgery or therapeutic catheterisation for congenital heart disease in children in the United Kingdom: analysis of the central cardiac audit database for 2000-1. BMJ 2004;328: 611-5.[Abstract/Free Full Text]

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