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Risk-Adjustment for Swedish In-Hospital Trauma Mortality using International Classification of disease Injury Severity Score (ICISS): issues with description and methods
Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction

Different methods have been used to describe the epidemiology of trauma with varying results. Crude mortality outcome data differ significantly from risk-adjusted information. A previous standard method for risk-adjustment in trauma was the Injury Severity Score (ISS), although it has several shortcomings. In this thesis I examine Swedish injury statistics from an epidemiological perspective using crude and risk-adjusted mortality, and to adjust for injury I used the International Classification of disease Injury Severity Score (ICISS). The groups of most lethal injuries (fall, traffic, and assault) were examined separately using an ICISS mortality prediction model that focused particularly on the effects on the prediction of mortality by adding coexisting conditions (comorbidity) to it. Differences in mortality between the sexes and changes over time were tested separately.

Material and Methods

Data from all patients with ICD-10 based diagnoses of injury (ICD-10: V01 to Y36) in the Swedish National Patient Registry and Cause of Death Registry were collected from 1999 to 2012 and used for assessment of mortality and comorbidity. A subgroup (patients in hospital) from 2001-2011 were selected as the study group. Their injuries were in the subgroups of falls, traffic, and assaults, and are the focus of this thesis. Mortality within 30 days of injury was used as the endpoint. The severity of injury was adjusted for using the ICISS, which was first described by Osler et al. The model was also adjusted for age, sex, and comorbidities.

Results

The study group comprised 815 846 patients (of whom 17 721 died). There was a decrease over time in injuries caused by falls and traffic (coefficient -4.71, p=0.047 and coefficient -5.37, p<0.001), whereas there was no change in assault-related injuries/100 000 inhabitants. The risk-adjusted 30-day mortality showed a decrease in injuries related to traffic and assault (OR 0.95, p<0.001 and OR 0.93, p=0.022) whereas for falls it remained unchanged. There was also a risk-adjusted survival benefit for women, which increased with increasing age. Adjusting for comorbidities made the prediction of 30-day mortality by the ICISS model better (accuracy, calibration, and discrimination). However, most of this effect was found to be the result of the other characteristics of the fall related injury group (they were older, and had more coexisting conditions).

Conclusion

During a 10-year period, there has been a significant overall decrease in crude as well as risk-adjusted mortality for these three injury groups combined. Within these groups there is a clear, risk-adjusted, female survival advantage. The ICISS model for the prediction of mortality improves when comorbidities are added, but this effect is minor and seen mainly among the injuries caused by falls, where comorbidity is significant. The ICISS method was a valuable adjunct in the investigation of data on Swedish mortality after injury that has been gathered from health care registry data.

Abstract [sv]

Introduktion

Olika metoder har använts för att beskriva trauma, alla med varierande resultat. Riskjusterad respektive icke-justerad data skiljer sig markant åt. En metod som oftast används för riskjustering i traumasammanhang är Injury Severity Score (ISS) som tyvärr är belastad med ett antal praktiska tillkortakommande. I denna avhandling har jag undersökt de skadade i Sverige från ett epidemiologiskt perspektiv med både justerad och icke riskjusterad mortalitet. För att kunna justera för skadan använde jag International Classification of disease Injury Severity Score (ICISS). De dödligaste skademekanismerna i Sverige (fall, trafik och övergrepp) analyserades för sig med hjälp av en mortalitetsjusterad modell baserad på ICISS som fokuserade särskilt på mortalitetseffekterna av att lägga till tidigare sjukdomar (komorbiditet) i modellen. Skillnader i dödlighet mellan de olika könen samt förändringar över tid undersöktes.

Material och Metod

Information om alla patienter med en skadekod från ICD-10 systemet (ICD10: V01-Y36) i slutenvårdsregistret eller dödsorsaksregistrets under åren 1999–2012 samlades in för att användas för att kunna utvärdera mortalitet och komorbiditet. En undergrupp av sjukhusinlagda patienter från 2001–2011 valdes sedan som primär studiegrupp. De som i denna grupp hade drabbats av fall-, trafik- eller övergrepps-relaterade skador är det denna avhandling fokuserar på. Som mätpunkt (endpoint) användes avliden inom 30 dagar från skadan. Skadans allvarlighetsgrad bedömdes med ICISS som Osler var först att beskriva. Modellen justerades även för ålder, kön och komorbiditet.

Resultat

Studiegruppen innehöll 815 846 patienter (av vilka 17 721 avled). I gruppen med falloch trafik-relaterade skador var det en ren minskning över studietiden (koefficienten -4,71 med ett p=0,047 och med en koefficient på -5,37 med ett p <0,001), medans i övergreppsrelaterade skador kunde jag inte hitta någon minskning per 100 000 invånare. Den riskjusterade 30-dagars dödligheten hade en minskning i trafik- och övergreppsrelaterade skador (OR 0,95 med ett p <0,001 respektive OR 0,93 med ett p=0,022) men ingen minskning i fallrelaterade skador sågs. Riskjusterat gick det också att hitta en överlevnadsfördel för kvinnor, vilken ökade med ålder. När jag justerade för komorbiditeter blev prediktionsmodellen för ICISS med 30-dagars dödlighet bättre (detta gällde både precision, kalibrering och diskriminering). Det bör dock nämnas att det mesta av förbättringen vid eftergranskning var beroende på fall gruppens demografi (högre ålder och mer komorbiditeter).

Konklusion

Under denna tio-årsperiod har dödligheten minskat för dessa grupper, både riskjusterat och icke justerat. Inom dessa grupper finns en tydlig riskjusterad överlevnadsfördel för kvinnor. ICISS-modellen blir bättre på att förutspå 30-dagars dödlighet när man lägger till komorbiditet, men effekten är att betrakta som en mindre effekt och ses tydligast i fallrelaterade skador (där ålder och komorbiditet är högre). Metoden med ICISS är en värdefull metod för att undersöka stora datamaterial och dödlighet i stora grupper i Sverige. Detta kan göras med redan insamlade data i sjukvårdsregistren.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. , p. 77
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1660
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
URN: urn:nbn:se:liu:diva-154415DOI: 10.3384/diss.diva-154415ISBN: 9789176851401 (print)OAI: oai:DiVA.org:liu-154415DiVA, id: diva2:1287490
Public defence
2019-02-15, Granitsalen, Campus US, Linköping, 09:00 (English)
Opponent
Supervisors
Note

Minor corrections are made in the electronic version of the thesis. / Mindre korreigeringar är gjorda i den elektroniska versionen av avhandlingen.

Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-02-11Bibliographically approved
List of papers
1. Deaths caused by injury among people of working age (18-64) are decreasing, while those among older people (64+) are increasing
Open this publication in new window or tab >>Deaths caused by injury among people of working age (18-64) are decreasing, while those among older people (64+) are increasing
Show others...
2018 (English)In: European Journal of Trauma and Emergency Surgery, ISSN 1863-9933, E-ISSN 1863-9941, Vol. 44, no 4, p. 589-596Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Injury is an important cause of death in all age groups worldwide, and contributes to many losses of human and economic resources. Currently, we know a few data about mortality from injury, particularly among the working population. The aim of the present study was to examine death from injury over a period of 14 years (1999-2012) using the Swedish Cause of Death Registry (CDR) and the National Patient Registry, which have complete national coverage.

METHOD: CDR was used to identify injury-related deaths among adults (18 years or over) during the years 1999-2012. ICD-10 diagnoses from V01 to X39 were included. The significance of changes over time was analyzed by linear regression.

RESULTS: The incidence of prehospital death decreased significantly (coefficient -0.22, r (2) = 0.30; p = 0.041) during the study period, while that of deaths in hospital increased significantly (coefficient 0.20, r (2) = 0.75; p < 0.001). Mortality/100,000 person-years in the working age group (18-64 years) decreased significantly (coefficient -0.40, r (2) = 0.37; p = 0.020), mainly as a result of decrease in traffic-related deaths (coefficient -0.34, r (2) = 0.85; p < 0.001). The incidence of deaths from injury among elderly (65 years and older) patients increased because of the increase in falls (coefficient 1.71, r (2) = 0.84; p < 0.001) and poisoning (coefficient 0.13, r (2) = 0.69; p < 0.001).

CONCLUSION: The epidemiology of injury in Sweden has changed during recent years in that mortality from injury has declined in the working age group and increased among those people 64 years old and over.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Elderly, Injury, Mortality, Prehospital, Trauma, Working age
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:liu:diva-142763 (URN)10.1007/s00068-017-0827-1 (DOI)000440981100014 ()28825159 (PubMedID)2-s2.0-85027836250 (Scopus ID)
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2019-02-11Bibliographically approved
2. Decreased risk adjusted 30-day mortality for hospital admitted injuries: a multi-centre longitudinal study
Open this publication in new window or tab >>Decreased risk adjusted 30-day mortality for hospital admitted injuries: a multi-centre longitudinal study
Show others...
2018 (English)In: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, ISSN 1757-7241, E-ISSN 1757-7241, Vol. 26, no 1, article id 24Article in journal (Refereed) Published
Abstract [en]

Background: The interpretation of changes in injury-related mortality over time requires an understanding of changes in the incidence of the various types of injury, and adjustment for their severity. Our aim was to investigate changes over time in incidence of hospital admission for injuries caused by falls, traffic incidents, or assaults, and to assess the risk-adjusted short-term mortality for these patients.less thanbr /greater thanMethods: All patients admitted to hospital with injuries caused by falls, traffic incidents, or assaults during the years 2001-11 in Sweden were identified from the nationwide population-based Patient Registry. The trend in mortality over time for each cause of injury was adjusted for age, sex, comorbidity and severity of injury as classified from the International Classification of diseases, version 10 Injury Severity Score (ICISS).less thanbr /greater thanResults: Both the incidence of fall (689 to 636/100000 inhabitants: p = 0.047, coefficient - 4.71) and traffic related injuries (169 to 123/100000 inhabitants: p less than 0.0001, coefficient - 5.37) decreased over time while incidence of assault related injuries remained essentially unchanged during the study period. There was an overall decrease in risk-adjusted 30-day mortality in all three groups (OR 1.00; CI95% 0.99-1.00). Decreases in traffic (OR 0.95; 95% CI 0.93 to 0.97) and assault (OR 0.93; 95% CI 0.87 to 0.99) related injuries was significant whereas falls were not during this 11-year period.less thanbr /greater thanDiscussion: Risk-adjustment is a good way to use big materials to find epidemiological changes. However after adjusting for age, year, sex and risk we find that a possible factor is left in the pre- and/or in-hospital care.less thanbr /greater thanConclusions: The decrease in risk-adjusted mortality may suggest changes over time in pre- and/or in-hospital care. A non-significantdecrease in risk-adjusted mortality was registered for falls, which may indicate that low-energy trauma has not benefited for the increased survivability as much as high-energy trauma, ie traffic- and assault related injuries.

National Category
Surgery
Identifiers
urn:nbn:se:liu:diva-146965 (URN)10.1186/s13049-018-0485-2 (DOI)000429285700002 ()29615089 (PubMedID)
Available from: 2018-04-09 Created: 2018-04-09 Last updated: 2019-02-11

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