Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.

<h4>Background</h4>The standardized mortality ratio (SMR) is often used to assess and compare hospital performance. While it has been recognized that hospitals may differ in their SMRs due to differences in patient composition, there is a lack of rigorous analysis of this and other-large...

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Autores principales:	Martin Roessler, Jochen Schmitt, Olaf Schoffer
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/36b4645df37249e194af9d13f014d6a9
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spelling	oai:doaj.org-article:36b4645df37249e194af9d13f014d6a92021-12-02T20:08:28ZCan we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.1932-620310.1371/journal.pone.0257003https://doaj.org/article/36b4645df37249e194af9d13f014d6a92021-01-01T00:00:00Zhttps://doi.org/10.1371/journal.pone.0257003https://doaj.org/toc/1932-6203<h4>Background</h4>The standardized mortality ratio (SMR) is often used to assess and compare hospital performance. While it has been recognized that hospitals may differ in their SMRs due to differences in patient composition, there is a lack of rigorous analysis of this and other-largely unrecognized-properties of the SMR.<h4>Methods</h4>This paper proposes five axiomatic requirements for adequate standardized mortality measures: strict monotonicity (monotone relation to actual mortality rates), case-mix insensitivity (independence of patient composition), scale insensitivity (independence of hospital size), equivalence principle (equal rating of hospitals with equal actual mortality rates in all patient groups), and dominance principle (better rating of unambiguously better performing hospitals). Given these axiomatic requirements, effects of variations in patient composition, hospital size, and actual and expected mortality rates on the SMR were examined using basic algebra and calculus. In this regard, we distinguished between standardization using expected mortality rates derived from a different dataset (external standardization) and standardization based on a dataset including the considered hospitals (internal standardization). The results were illustrated by hypothetical examples.<h4>Results</h4>Under external standardization, the SMR fulfills the axiomatic requirements of strict monotonicity and scale insensitivity but violates the requirement of case-mix insensitivity, the equivalence principle, and the dominance principle. All axiomatic requirements not fulfilled under external standardization are also not fulfilled under internal standardization. In addition, the SMR under internal standardization is scale sensitive and violates the axiomatic requirement of strict monotonicity.<h4>Conclusions</h4>The SMR fulfills only two (none) out of the five proposed axiomatic requirements under external (internal) standardization. Generally, the SMRs of hospitals are differently affected by variations in case mix and actual and expected mortality rates unless the hospitals are identical in these characteristics. These properties hamper valid assessment and comparison of hospital performance based on the SMR.Martin RoesslerJochen SchmittOlaf SchofferPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 16, Iss 9, p e0257003 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Martin Roessler Jochen Schmitt Olaf Schoffer Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.
description	<h4>Background</h4>The standardized mortality ratio (SMR) is often used to assess and compare hospital performance. While it has been recognized that hospitals may differ in their SMRs due to differences in patient composition, there is a lack of rigorous analysis of this and other-largely unrecognized-properties of the SMR.<h4>Methods</h4>This paper proposes five axiomatic requirements for adequate standardized mortality measures: strict monotonicity (monotone relation to actual mortality rates), case-mix insensitivity (independence of patient composition), scale insensitivity (independence of hospital size), equivalence principle (equal rating of hospitals with equal actual mortality rates in all patient groups), and dominance principle (better rating of unambiguously better performing hospitals). Given these axiomatic requirements, effects of variations in patient composition, hospital size, and actual and expected mortality rates on the SMR were examined using basic algebra and calculus. In this regard, we distinguished between standardization using expected mortality rates derived from a different dataset (external standardization) and standardization based on a dataset including the considered hospitals (internal standardization). The results were illustrated by hypothetical examples.<h4>Results</h4>Under external standardization, the SMR fulfills the axiomatic requirements of strict monotonicity and scale insensitivity but violates the requirement of case-mix insensitivity, the equivalence principle, and the dominance principle. All axiomatic requirements not fulfilled under external standardization are also not fulfilled under internal standardization. In addition, the SMR under internal standardization is scale sensitive and violates the axiomatic requirement of strict monotonicity.<h4>Conclusions</h4>The SMR fulfills only two (none) out of the five proposed axiomatic requirements under external (internal) standardization. Generally, the SMRs of hospitals are differently affected by variations in case mix and actual and expected mortality rates unless the hospitals are identical in these characteristics. These properties hamper valid assessment and comparison of hospital performance based on the SMR.
format	article
author	Martin Roessler Jochen Schmitt Olaf Schoffer
author_facet	Martin Roessler Jochen Schmitt Olaf Schoffer
author_sort	Martin Roessler
title	Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.
title_short	Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.
title_full	Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.
title_fullStr	Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.
title_full_unstemmed	Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.
title_sort	can we trust the standardized mortality ratio? a formal analysis and evaluation based on axiomatic requirements.
publisher	Public Library of Science (PLoS)
publishDate	2021
url	https://doaj.org/article/36b4645df37249e194af9d13f014d6a9
work_keys_str_mv	AT martinroessler canwetrustthestandardizedmortalityratioaformalanalysisandevaluationbasedonaxiomaticrequirements AT jochenschmitt canwetrustthestandardizedmortalityratioaformalanalysisandevaluationbasedonaxiomaticrequirements AT olafschoffer canwetrustthestandardizedmortalityratioaformalanalysisandevaluationbasedonaxiomaticrequirements
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Can we trust the standardized mortality ratio? A formal analysis and evaluation based on axiomatic requirements.

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