Intended for healthcare professionals


Annual league tables of mortality in neonatal intensive care units: longitudinal study

BMJ 1998; 316 doi: (Published 27 June 1998) Cite this as: BMJ 1998;316:1931
  1. Gareth J Parry (g.parry{at}, research fellow in health services researcha,
  2. Craig R Gould, data managerc,
  3. Chris J McCabe, lecturer in health economicsb,
  4. William O Tarnow-Mordi, reader in neonatal medicine and perinatal epidemiology on behalf of the International Neonatal Network and the Scottish Neonatal Consultants and Nurses Collaborative Study Group.c
  1. a Medical Care Research Unit, School of Health and Related Research, University of Sheffield, Sheffield S3 7XL,
  2. b Sheffield Health Economics Group, School of Health and Related Research,
  3. c Department of Child Health, Ninewells Hospital and Medical School, Dundee DD1 9SY
  1. Correspondence to: Mr Parry
  • Accepted 12 February 1998


Objective: To assess whether crude league tables of mortality and league tables of risk adjusted mortality accurately reflect the performance of hospitals.

Design: Longitudinal study of mortality occurring in hospital.

Setting: 9 neonatal intensive care units in the United Kingdom.

Subjects: 2671 very low birth weight or preterm infants admitted to neonatal intensive care units between 1988 and 1994.

Main outcome measures: Crude hospital mortality and hospital mortality adjusted using the clinical risk index for babies (CRIB) score.

Results: Hospitals had wide and overlapping confidence intervals when ranked by mortality in annual league tables; this made it impossible to discriminate between hospitals reliably. In most years there was no significant difference between hospitals, only random variation. The apparent performance of individual hospitals fluctuated substantially from year to year.

Conclusions: Annual league tables are not reliable indicators of performance or best practice; they do not reflect consistent differences between hospitals. Any action prompted by the annual league tables would have been equally likely to have been beneficial, detrimental, or irrelevant. Mortality should be compared between groups of hospitals using specific criteria—such as differences in the volume of patients, staffing policy, training of staff, or aspects of clinical practice—after adjusting for risk. This will produce more reliable estimates with narrower confidence intervals, and more reliable and rapid conclusions.

Key messages

  • League tables are being used increasingly to evaluate hospital performance in the United Kingdom

  • In annual league tables the rankings of nine neonatal intensive care units in different hospitals had wide and overlapping confidence intervals and their rankings fluctuated substantially over six years

  • Annual league tables of hospital mortality were inherently unreliable for comparing hospital performance or for indicating best practices

  • The UK government's commitment to using annual league tables of outcomes such as mortality to monitor services and the spread of best practices should be reconsidered

  • Prospective studies of risk adjusted outcome in hospitals grouped according to specific characteristics would provide better information and be a better use of resources


  • Accepted 12 February 1998
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