Hospital admissions in the National Health Survey and hospital separations in the National Hospital Morbidity Dataset: What is the difference?
Article first published online: 10 JUN 2008
© 2008 The Authors. Journal Compilation © 2008 Public Health Association of Australia
Australian and New Zealand Journal of Public Health
Volume 32, Issue 3, pages 276–281, June 2008
How to Cite
Ranmuthugala, G., Brown, L., Lymer, S. and Thurecht, L. (2008), Hospital admissions in the National Health Survey and hospital separations in the National Hospital Morbidity Dataset: What is the difference?. Australian and New Zealand Journal of Public Health, 32: 276–281. doi: 10.1111/j.1753-6405.2008.00229.x
- Issue published online: 10 JUN 2008
- Article first published online: 10 JUN 2008
- Submitted: October 2007 Revision requested: January 2008 Accepted: April 2008
- Hospital surveys;
- hospital separations;
- population surveillance;
- population register;
Objective: To compare the National Health Survey (NHS) derived estimates of hospital admissions with the number of hospital separations registered in the National Hospital Morbidity Dataset (NHMD).
Methods: Using the person weights in the NHS, the Expanded Confidential Unit Record File of the 2004–05 NHS was used to derive a population estimate of the number of hospital admissions in the 12 months preceding the conduct of the survey. These estimates, by age and sex categories and whether or not the admission involved an overnight stay, were compared with the number of hospital separations registered in the NHMD.
Results: The number of hospital admissions estimated from the NHS was approximately two thirds the number of hospital separations registered in the NHMD. The discrepancy between the two data sources was greater when hospital episodes did not involve an overnight stay in hospital.
Conclusion: There are systematic differences between the number of admissions/separations derived by the NHS and the NHMD for reasons including the technical difference between a hospital admission and a separation, and the sampling frame and scope of the NHS. Researchers looking for individual level data on hospital utilisation must take note of the differences between NHS and the NHMD, and recognise that there are methods to simulate a representative population by enhancing an existing dataset with information from multiple data sources, thus providing researchers a cost-effective data resource.