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  3. Including post-discharge mortality in calculation of hospital standardised mortality ratios: retrospective analysis of hospital episode statistics
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Research

Including post-discharge mortality in calculation of hospital standardised mortality ratios: retrospective analysis of hospital episode statistics

BMJ 2013; 347 doi: https://doi.org/10.1136/bmj.f5913 (Published 21 October 2013) Cite this as: BMJ 2013;347:f5913
  1. Maurice E Pouw, resident1,
  2. L M Peelen, post-doctoral researcher2,
  3. K G M Moons, professor of clinical epidemiology2,
  4. C J Kalkman, professor of anesthesiology1,
  5. H F Lingsma, post-doctoral researcher3
  1. 1Department of Anesthesiology, University Medical Center Utrecht, Heidelberglaan 100, PO Box 85500, 3508 GA Utrecht, Netherlands
  2. 2Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands
  3. 3Department of Public Health, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, Netherlands
  1. Correspondence to: M E Pouw M.Pouw{at}umcutrecht.nl
  • Accepted 2 September 2013

Abstract

Objectives To assess the consequences of applying different mortality timeframes on standardised mortality ratios of individual hospitals and, secondarily, to evaluate the association between in-hospital standardised mortality ratios and early post-discharge mortality rate, length of hospital stay, and transfer rate.

Design Retrospective analysis of routinely collected hospital data to compare observed deaths in 50 diagnostic categories with deaths predicted by a case mix adjustment method.

Setting 60 Dutch hospitals.

Participants 1 228 815 patients discharged in the period 2008 to 2010.

Main outcome measures In-hospital standardised mortality ratio, 30 days post-admission standardised mortality ratio, and 30 days post-discharge standardised mortality ratio.

Results Compared with the in-hospital standardised mortality ratio, 33% of the hospitals were categorised differently with the 30 days post-admission standardised mortality ratio and 22% were categorised differently with the 30 days post-discharge standardised mortality ratio. A positive association was found between in-hospital standardised mortality ratio and length of hospital stay (Pearson correlation coefficient 0.33; P=0.01), and an inverse association was found between in-hospital standardised mortality ratio and early post-discharge mortality (Pearson correlation coefficient −0.37; P=0.004).

Conclusions Applying different mortality timeframes resulted in differences in standardised mortality ratios and differences in judgment regarding the performance of individual hospitals. Furthermore, associations between in-hospital standardised mortality rates, length of stay, and early post-discharge mortality rates were found. Combining these findings suggests that standardised mortality ratios based on in-hospital mortality are subject to so-called “discharge bias.” Hence, early post-discharge mortality should be included in the calculation of standardised mortality ratios.

Footnotes

  • Contributors MEP conceived and designed the statistical analysis plan, analysed the data, and drafted and revised the paper. LMP and KGMM analysed the data and revised the paper. CJK and HFL analysed the data and drafted and revised the paper. All authors contributed to the final manuscript. MEP is the guarantor.

  • Funding: This study was part of a study commissioned by the Dutch Ministry of Health, Welfare and Sport. The ministry had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the article for publication.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Not needed.

  • Data sharing: Technical appendix and statistical code are available (after permission from Statistics Netherlands and the DHD) from the corresponding author at m.pouw{at}umcutrecht.nl. The dataset is available on request via the DHD (www.dutchhospitaldata.nl).

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 3.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/3.0/.

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