How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway

Objective The prescription-based Rx-risk index has previously been developed to measure multimorbidity. We aimed to adapt and evaluate the validity of the Rx-risk index in prediction of mortality among persons with type 2 diabetes.Design Registry-based study.Setting Adults with type 2 diabetes in No...

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Main Authors: Anne Karen Jenum, Jannicke Igland, Marjolein Memelink Iversen, Jan Ivar Røssberg, Ragnhild B Strandberg, Tore Julsrud Berg, Esben Selmer Buhl, Rachel Forster
Format: Article
Language:English
Published: BMJ Publishing Group 2024-03-01
Series:BMJ Open
Online Access:https://bmjopen.bmj.com/content/14/3/e077027.full
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author Anne Karen Jenum
Jannicke Igland
Marjolein Memelink Iversen
Jan Ivar Røssberg
Ragnhild B Strandberg
Tore Julsrud Berg
Esben Selmer Buhl
Rachel Forster
author_facet Anne Karen Jenum
Jannicke Igland
Marjolein Memelink Iversen
Jan Ivar Røssberg
Ragnhild B Strandberg
Tore Julsrud Berg
Esben Selmer Buhl
Rachel Forster
author_sort Anne Karen Jenum
collection DOAJ
description Objective The prescription-based Rx-risk index has previously been developed to measure multimorbidity. We aimed to adapt and evaluate the validity of the Rx-risk index in prediction of mortality among persons with type 2 diabetes.Design Registry-based study.Setting Adults with type 2 diabetes in Norway identified within the ‘Outcomes and Multimorbidity In Type 2 diabetes’ cohort, with linkage to prescriptions from the Norwegian Prescription Database and mortality from the Population Registry.Participants We defined a calibration sample of 42 290 adults diagnosed with type 2 diabetes 1950–2013, and a temporal validation sample of 7085 adults diagnosed 2014–2016 to evaluate the index validity over timePrimary outcome measure All-cause mortalityMethods For the calibration sample, dispensed drug prescriptions in 2013 were used to define 44 morbidity categories. Weights were estimated using regression coefficients from a Cox regression model with 5 year mortality as the outcome and all morbidity categories, age and sex included as covariates. The Rx-risk index was computed as a weighted sum of morbidities. The validity of the index was evaluated using C-statistic and calibration plots.Results In the calibration sample, mean (SD) age at start of follow-up and duration of diabetes was 63.8 (12.4) and 10.1 (7.0) years, respectively. The overall C-statistic was 0.82 and varied from 0.74 to 0.85 when stratifying on age groups, sex, level of education and country of origin. In the validation sample, mean (SD) age and duration of diabetes was 59.7 (13.0) and 2.0 (0.8) years, respectively. Despite younger age, shorter duration of diabetes and later time period, the C-index was high both in the total sample (0.84) and separately for men (0.83) and women (0.84).Conclusions The Rx-risk index showed good discrimination and calibration in predicting mortality and thus presents a valid tool to assess multimorbidity among persons with type 2 diabetes.
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spelling doaj.art-d4b0b1fe47ac4df7bc2a7c3d1bb5b0f02024-04-04T02:00:09ZengBMJ Publishing GroupBMJ Open2044-60552024-03-0114310.1136/bmjopen-2023-077027How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from NorwayAnne Karen Jenum0Jannicke Igland1Marjolein Memelink Iversen2Jan Ivar Røssberg3Ragnhild B Strandberg4Tore Julsrud Berg5Esben Selmer Buhl6Rachel Forster7Department of General Practice, University of Oslo, Oslo, NorwayDepartment of Health and Caring Sciences, Western Norway University of Applied Sciences, Bergen, Hordaland, NorwayDepartment of Health and Caring Sciences, Western Norway University of Applied Sciences, Bergen, NorwayInstitute of Clinical Medicine, University of Oslo, Oslo, NorwayDepartment of Health and Caring Sciences, Western Norway University of Applied Sciences, Bergen, NorwayFaculty of Medicine, University of Oslo, Oslo, NorwayGeneral Practice Research Unit, Oslo, NorwayDepartment of Health and Caring Sciences, Western Norway University of Applied Sciences, Bergen, Hordaland, NorwayObjective The prescription-based Rx-risk index has previously been developed to measure multimorbidity. We aimed to adapt and evaluate the validity of the Rx-risk index in prediction of mortality among persons with type 2 diabetes.Design Registry-based study.Setting Adults with type 2 diabetes in Norway identified within the ‘Outcomes and Multimorbidity In Type 2 diabetes’ cohort, with linkage to prescriptions from the Norwegian Prescription Database and mortality from the Population Registry.Participants We defined a calibration sample of 42 290 adults diagnosed with type 2 diabetes 1950–2013, and a temporal validation sample of 7085 adults diagnosed 2014–2016 to evaluate the index validity over timePrimary outcome measure All-cause mortalityMethods For the calibration sample, dispensed drug prescriptions in 2013 were used to define 44 morbidity categories. Weights were estimated using regression coefficients from a Cox regression model with 5 year mortality as the outcome and all morbidity categories, age and sex included as covariates. The Rx-risk index was computed as a weighted sum of morbidities. The validity of the index was evaluated using C-statistic and calibration plots.Results In the calibration sample, mean (SD) age at start of follow-up and duration of diabetes was 63.8 (12.4) and 10.1 (7.0) years, respectively. The overall C-statistic was 0.82 and varied from 0.74 to 0.85 when stratifying on age groups, sex, level of education and country of origin. In the validation sample, mean (SD) age and duration of diabetes was 59.7 (13.0) and 2.0 (0.8) years, respectively. Despite younger age, shorter duration of diabetes and later time period, the C-index was high both in the total sample (0.84) and separately for men (0.83) and women (0.84).Conclusions The Rx-risk index showed good discrimination and calibration in predicting mortality and thus presents a valid tool to assess multimorbidity among persons with type 2 diabetes.https://bmjopen.bmj.com/content/14/3/e077027.full
spellingShingle Anne Karen Jenum
Jannicke Igland
Marjolein Memelink Iversen
Jan Ivar Røssberg
Ragnhild B Strandberg
Tore Julsrud Berg
Esben Selmer Buhl
Rachel Forster
How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway
BMJ Open
title How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway
title_full How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway
title_fullStr How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway
title_full_unstemmed How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway
title_short How valid is a prescription-based multimorbidity index (Rx-risk) in predicting mortality in the Outcomes and Multimorbidity In Type 2 diabetes (OMIT) study? A nation-wide registry-based cohort study from Norway
title_sort how valid is a prescription based multimorbidity index rx risk in predicting mortality in the outcomes and multimorbidity in type 2 diabetes omit study a nation wide registry based cohort study from norway
url https://bmjopen.bmj.com/content/14/3/e077027.full
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