Psychometric properties of the Shared Decision-Making Questionnaire (SDM-Q-9) in oncology practice

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making www.elsevier.es/ijchp

International Journal

of Clinical and Health Psychology

Psychometric properties of the Shared Decision-Making Questionnaire (SDM-Q-9) in oncology practice

Caterina Calderon

^a^,∗

, Paula Jiménez-Fonseca

^b

, Pere Joan Ferrando

^c

, Carlos Jara

^d

, Urbano Lorenzo-Seva

^c

, Carmen Beato

^e

, Teresa García-García

^f

, Beatriz Castelo

^g

, Avinash Ramchandani

^h

, María Mar Mu˜ noz

ⁱ

, Eva Martínez de Castro

^j

,

Ismael Ghanem

^g

, Montse Mangas

^k

, Alberto Carmona-Bayonas

^f

aDepartmentofClinicalPsychologyandPsychobiology.FacultyofPsychology.UniversityofBarcelona,Spain

bDepartmentofMedicalOncology.HospitalUniversitarioCentralofAsturias,Oviedo,Spain

cFacultyofPsychology.RoviraandVirgiliUniversity,Tarragona,Spain

dDepartmentofMedicalOncology.HospitalUniversitarioFundaciónAlcorcón,UniversidadReyJuanCarlos,Madrid,Spain

eDepartmentofMedicalOncology.HospitalGrupoQuirón,Sevilla,Spain

fDepartmentofMedicalOncology.HospitalUniversitarioMoralesMeseguer,Murcia,Spain

gDepartmentofMedicalOncology.HospitalUniversitarioLaPaz,Madrid,Spain

hDepartmentofMedicalOncology.HospitalUniversitarioInsulardeGranCanaria,LasPalmas,Spain

iDepartmentofMedicalOncology.HospitalVirgendeLaLuz,Cuenca,Spain

jDepartmentofMedicalOncology.HospitalUniversitarioMarquésdeValdecilla,Santander,Spain

kDepartmentofMedicalOncology.HospitalGaldakao-Usansolo,Galdakao-Usansolo,Spain

Received1October2017;accepted19December2017

KEYWORDS Cancer;

Patientperspective;

Patient-physician relationship;

Shared

decision-making;

Instrumentalstudy

Abstract Background/Objective: This study sought to assess the psychometric properties of the 9-item Shared Decision-Making Questionnaire (SDM-Q-9) in patients with resected, non-metastatic cancer and eligible for adjuvant chemotherapy. Method: A total of 568 patients were recruited from a multi-institutional, prospective, transversal study. Patients answered the SDM-Q-9 after visiting their medical oncologist who, inturn, completed the SDM-Q---Physicianversion.Reliability,factorialstructures[exploratoryfactoranalysis(EFA),con- ﬁrmatoryfactoranalysis(CFA)],andconvergentvalidityoftheSDM-Q-9scoreswereexplored.

∗Correspondingauthor:DepartmentofClinicalPsychologyandPsychobiology.FacultyofPsychology.UniversityofBarcelona.Passeigde laValld’Hebron,171.08035Barcelona,Spain.

E-mailaddress:ccalderon@ub.edu(C.Calderon).

https://doi.org/10.1016/j.ijchp.2017.12.001

1697-2600/©2018PublishedbyElsevierEspaña,S.L.U.onbehalfofAsociaciónEspañoladePsicolog´ıaConductual.Thisisanopenaccess articleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making Results:SDM-Q-9showedaclearfactorialstructure,compatiblewithastrongandreplicable generalfactorandasecondarygroupfactor,inpatientswithresected,non-metastaticcancer.

Totalsumscoresderivedfromthegeneralfactorshowed goodreliabilityintermsofomega coefﬁcient:.90.TheassociationbetweenpatientandphysicianperceptionofSDMwasweak andfailedtoreachstatisticalsigniﬁcance.Malesandpatientsover60yearsofagedisplayedthe greatestsatisfactionwithSDM.Conclusions:SDM-Q-9canaidinevaluatingSDMfromthecancer patients’perspective.SDM-Q-9ishelpfulinstudiesexaminingpatientperspectivesofSDMand asanindicatorofthedegreeofqualityandsatisfactionwithhealthcareandpatient-physician relationship.

org/licenses/by-nc-nd/4.0/).

PALABRASCLAVE Cáncer;

perspectivadel paciente;

relación

médico-paciente;

tomadedecisiones compartida;

estudioinstrumental

PropiedadespsicométricasdelQuestionnaireSharedDecision-Making(SDM-Q-9)en oncología

Resumen Antecedentes/Objetivo: Este estudio analiza las propiedades psicométricas del Questionnaire Shared Decision-Making (SDM-Q-9) en pacientes con cáncer resecado, no metastásico y elegible para quimioterapia adyuvante. Métodos: Un total de 568 pacientes fueron reclutadosen un estudiomulti-institucional,prospectivo,transversal. Los pacientes respondieronalSDM-Q-9despuésdevisitarasuoncólogoque,asuvez,completóelSDM-Q- versiónmédico.Seestudiaronlaﬁabilidad,laestructurafactorial(análisisfactorialexploratorio yanálisisfactorialconﬁrmatorio)yla validezconvergentedelaspuntuacionesdelSDM-Q-9.

Resultados:LaescalaSDM-Q-9mostróunaestructurafactorialclara,compatibleconunfactor generalfuerteyreplicableyunfactordegruposecundario,enpacientesconcáncerresecado ynometastásico.Lapuntuacióndelfactorgeneralmostróunabuenafiabilidadentérminos decoeficienteomega:0,90.Laasociaciónentrelapercepcióndelmédicoydelpacienteenla SDMfuedébilynologróalcanzarsignificaciónestadística.Loshombresylospacientesmayores de60añosmostraronmayorsatisfacciónconlatomadedecisióncompartida.Conclusiones:

SDM-Q-9puedeayudarenlaevaluacióndelatomadedecisióncompartidadesdelaperspectiva delospacientesdecáncerycomoindicadordelgradodecalidadysatisfacciónenelcuidado delasaludenlarelaciónmédico-paciente.

creativecommons.org/licenses/by-nc-nd/4.0/).

Recentyearshavewitnessedgrowinginterestinpatient participationinshareddecision-making(SDM;Elwynetal., 2014), which represents a shift in traditional forms of healthcare, moving from a paternalistic model to a more collaborative relationship. In this patient-physician alliance, the patient’s (and family’s) opinion implies the physician’s relinquishing part of their control, contin- ued negotiation, and empowering the patient to develop their autonomy (Coulter & Collins, 2011; Schuler et al., 2017). Shareddecision includes threeessential elements:

exchangeof information(personal and medical) between patient and physician, deliberation as to diagnostic and therapeuticoptions,andreachingaconsensus(Rodenburg- Vandenbusscheetal.,2015;Shay&Lafata,2015).

Themostcommoncauseofpatientdissatisfactionisnot beingdulyinformedabouttheirmedicalconditionandtreat- mentalternatives(Libertetal.,2017).Asurveyconducted in eight European countries revealed that most patients

wantedtoreceivemore information,aswell astopartic- ipate moreinthe decision-makingprocess,although their expectations about their involvement in healthcare deci- sionsdifferedsigniﬁcantlyacrosscountries;forexample,in Spain andPoland, patients preferredamore paternalistic modelthaninSwitzerlandorGermany(Coulter,Parsons,&

Askham,2008).Likewise,youngerpeopletendedtoprefer morepatient-basedcommunicationsthanolderpeople;this wasconsistentinallcountries(Elwynetal.,2014).

WhilegreateffortisdevotedtopromotingSDM,itrep- resentsanimportantchallengeforphysicians(Libertetal., 2017)andtheevidenceregardingitsimpactcontinuestobe scarce(Tamirisaetal.,2017).Morereliableandvalidtools arerequiredtoassessSDM’seffectivenessandshedgreater light on its phases and correlates. The nine-item Shared DecisionMakingQuestionnaire(SDM-Q-9)isaquestionnaire designed toprobethe SDM process(Kriston etal., 2010).

TheoriginalversionwasdevelopedinGermanyandbasedon

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making Elwyn’scompetencesmodelforpatientparticipationandon

additionalpsychologicaltheories(Kristonetal.,2010;Simon etal.,2006).This24-itemversionwasreviewedandreduced to a 9-item scale, the SDM-Q-9, which displays excellent internalconsistency,highinter-itemdiscriminationandfac- torialvalidity(Kristonetal.,2010;Scholl,Kriston,Dirmaier,

&Härter,2015).TheSDM-Q-9hasbecomeacommonlyused tool for measuringSDM in clinical practice and has been translatedintoseverallanguages,includingEnglish(Kriston etal.,2010;Scholl,Kriston,Dirmaier,Buchholz,& Härter, 2012)andSpanish(DelasCuevasetal.,2015).Todate,it hasnotbeenappliedorvalidatedincancerpatients.

Cancer is a leading public health problem, given its incidence and mortality worldwide(Jönsson, Hofmarcher, Lindgren, & Wilking, 2016). In non-metastatic cancer, surgery and adjuvant chemotherapy can be curative and temporarilyimpactquality-of-life,duetotreatment-related adverse effects or sequelae (Jönsson et al., 2016). Nev- ertheless, in this context of uncertainty about prognosis and emotional stress, patient-based communication and SDM regarding adjuvant therapy should not only increase patients’ degree of satisfaction, but also theirresilience, adherenceandtolerancetochemotherapy,andtheclinical courseoftheirdisease,inadditiontomitigatingrepercus- sionsontheirquality-of-life(Libertetal.,2017).Likewise, individualized treatments have proven to beneﬁt cancer patients’quality-of-life(DeTorre-Luque,Gambara,López,

&Cruzado,2016).

Thepresentinstrumentalstudy(Carretero-Dios&Pérez, 2005; Ramos-Álvarez, Moreno-Fernández, Valdés-Conroy,

& Catena, 2008) attempted to assess the psychometric propertiesofSharedDecisionMakingQuestionnaire-version patient(SDM-Q-9;Kristonetal.,2010)inSpanishpatients withresected,non-metastaticcancerwhowereeligibleto receive adjuvant chemotherapy. The properties assessed were:factorialstructure,reliabilityofthederivedscores, andconstructvalidity.

Method

Participants

Thesampleconsistedof568cancerpatients;59.8%(n=338) werewomenandtheaverageagewas59.1years(SD=12.1, range 26-84). Most patients were married or lived with a partner (77.1%) and had completed primary education (58.3%).The mostcommonemploymentstatuswasretired (60.0%).Thesample’sclinicalcharacteristicsrevealedthat the most common types of cancer were colon (40.5%, n=230), and breast (33.5%, n=190). All relevant socio- demographic and medical characteristics are included in Table1.

Patientswererecruitedby30medicaloncologistsfrom 14 Spanish hospitals; 78.1% (n=25) of these specialists were female; mean age was35 years (SD=7.4, range 27- 62 years), and 11.9 years of experience in caring for cancerpatients(SD=8.8,range3-37years).Mostweresuper- specialists (68.8%) working at a public, teaching hospital (53.1%).

Table1 Patientandphysiciancharacteristics.

Patientandphysiciancharacteristics n % Patientcharacteristics(n=568)

Age(mean;standarddeviation) 59.1 12.1 Gender

Male 230 40.5

Female 338 59.5

MaritalStatus

Married/partnered 438 77.1

Single 49 8.6

Widowed 48 8.5

Divorced/separated 33 5.8

Educationallevel

Primary 331 58.3

HighSchool 153 26.9

University 84 14.8

Employed

No 330 60.0

Tumorsite

Colon 230 40.5

Breast 190 33.5

Stomach 36 6.3

Others 112 19.7

Stage

I 128 22.5

II 193 34.0

III 232 40.8

Unknown 15 2.6

Timesincediagnosis(days,mean;SD) 90.9(126.1) Physiciancharacteristics(n=30)

Gender:Female 25 78.1

Medicaloncologist:specialized 22 68.8 Typeofhospital:teaching 17(53.1)

Age(years,mean;SD) 35.0(7.4)

Numberofyearsemployed(mean;SD) 11.9(8.8) Note.n:number,SD:standarddeviation,%:percentage.

Instruments

SDM-Q-9 is a brief,valid, and reliable questionnaire that evaluates theSDM process fromthe patient’s perspective (Kriston etal., 2010), adapted toSpanish (De las Cuevas etal.,2015).The questionnairecontainsnineitems,each describingonestepoftheSDMprocess(Simonetal.,2006), it was developed to assess the degree to which patients feel involved in the decision-making process. The items arescored from0to5 onasix-point Likert scale ranging fromcompletely disagree(0) tocompletely agree (5).

Standardscoringisasimplesumscorewithvaluesbetween 0and45.Internal-consistency(alpha)reliabilityestimates are generally high in patients with chronic diseases: .98 (Germany),.94(U.S.),and.88(Spain).

SDM Questionnaire-Physician’s version(SDM-Q-Doc) is a questionnaire that evaluates the physician’s perspective andhow well they follow SDM with their patients (Scholl et al., 2012). It was adapted and validated to Spanish

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making (Calderonetal.,2017).The questionnaireconsistsofnine

items,eachofwhichdescribesonestepoftheprocess.The itemsarescored from0to5onasix-pointLikertscale as

‘‘completely disagree’’(0) to‘‘completely agree’’ (5).A simplesum-scorewithpossiblevaluesbetween0and45is obtained.Inthisstudy,Cronbach’salphaforthescalewas .90.

SIS is a 4-item scale that was created to ascer- tainpatients’ degree of satisfaction withthe information providedbytheirphysicianaboutthedisease,riskofrecur- rence, side effects of treatment, and time dedicated to informing them. The scale provides two subscales: satis- factionwiththeinformationprovidedandsatisfactionwith thetimededicated.Itemsarescoredfrom0to4onaﬁve- pointLikertscalerangingfromcompletelydisagree(0)to

completely agree (4); the higherthe score,the greater the satisfactionwiththe information provided.The scale revealedaCronbach’salphavalueof.82inourstudy.

The patients’ medical and demographic variables included were: age, gender, marital status, educational level,occupationalsector,tumorsite,stage,andtimesince diagnosis. The oncologist-related variables included age, gender,yearsofexperience,areaofspecialization(general (treatingallkindsoftumors)vs.super-specialized(treating onespeciﬁc subtype of tumor) and typeof hospital (aca- demicvs.non-academic).

Procedure

Thisisamulti-institutional,prospective,transversal,obser- vational study that pooled consecutive patients recruited at 14 Spanish teaching hospitals from June 2015 to May 2017.Thestudyispartofaresearchprograminvestigating patientswithcancer; itis funded bythe Continuous Care Groupof theSpanishSociety ofMedicalOncology(SEOM).

ThestudywasapprovedbytheEthicsReviewBoardateach institutionandbytheSpanishAgencyofMedicinesandMedi- calDevices(AEMPS).Inclusioncriteriawerebeing≥18years of age, having a histologically conﬁrmed, non-advanced, solidtumorsurgicallytreatedforwhichinternationalclini- calguidelinesconsideradjuvanttreatmenttobeanoption.

Patients with metastatic disease, treated with preopera- tiveradio-orchemotherapy,orwithadjuvanthormonalor radiotherapy without chemotherapy were excluded. Simi- larly,physicalailments,comorbidity,and/orageprecluding chemotherapy, and personal, psychological, family, socio- logical,geographical,and/or underlyingmedicalcondition that, in the investigator’s opinion, could hinder the individual’sabilitytoparticipateinthestudywerealsocause forexclusion, sincethesepatientsdidnot havetodecide onadjuvanttherapy.The evaluation wasperformed inall casesapproximatelyonemonthfollowingsurgicalresection, in the context of patients’ ﬁrst visit with the oncologist todecide onadjuvantchemotherapy. Datacollectionpro- cedures were similar at all hospitals. Participation was voluntary,anonymous, and wouldnot affect their care in theslightest.Theparticipantscompletedthequestionnaires individually,withnolimitontime.Datawerecollectedand updatedbymedicaloncologists,speciﬁcallytrainedtocom- plywiththestudyrequirements,viaaweb-basedplatform (www.neocoping.es).Ofthe627patientsscreened,59were

noteligible(17didnotmeetinclusioncriteria;23metexclu- sioncriteriaand19hadincompletedata).

Dataanalysis

DescriptiveanalyseswereconductedforeverySMD-Q-9item and exploredmeans standard deviations and distributions oftheitemscores. Toassessthefactorialstructureofthe scale, thesample wasrandomly splitintotwogroups and differentExploratory FactorAnalysis(EFA)solutionsbased on previous reported results were performed on the first split-half sample.The adequacyoftheinter-itemcorrela- tionmatrix to befactor analyzed wasfirstassessed using the Kaiser-Meyer-Olkin (KMO) measure of sampling ade- quacy.Thedifferenthypothesizedsolutionswerenextfitted byusingrobust,unweighted leastsquaresestimationwith mean-and-variancecorrected fitstatisticsasimplemented in the FACTORprogram (Lorenzo-Seva & Ferrando, 2013).

They were: (a) unidimensional (as the scale was initially designed tobe single-trait), (b) unidimensionalwithitem 1omitted(DelasCuevasetal.,2015)and(c)bidimensional withcorrelatedfactors.FromtheEFAresults,asimpleand clearlyinterpretablebifactorstructure(Lorenzo-Seva&Fer- rando, 2013) could be speciﬁed. This structure was next ﬁttedtotheentiresamplewithFACTORbyusingthesame estimationproceduredescribedabove.

In all the tested solutions above, the goodness-of-fit indicesusedtoassessmodel-datafitwere:(a)RMSEA,with its 95% confidence interval(as a measure of approximate fit);(b)Goodness-offit-index(GFI),and(c)therootmean squareofthestandardizedresiduals(z-RMSR),(asabsolute measures of fit),and (d) the comparativefit index (CFI), (asarelativemeasureoffitwithrespecttothenullinde- pendence model).Wefollowedtheusualrules indeciding modelappropriateness(Schermelleh-Engel,Moosbrugger,&

Müller,2003).Inadditiontomodel-dataﬁtmeasures,addi- tionalindicesofappropriatenessforassessingthestrength andreplicabilityofthesolution(Hindex)aswellasclose- ness tounidimensionality (ECV index)were also obtained (Ferrando&Lorenzo-Seva,2017).

Oncetheproposedstructurehadbeen fittedandfound appropriate,scoresbasedonthisstructure wereobtained andtheirreliabilitywasassessedbyusingtheomegacoef- ficient (McDonald, 1999). Finally, construct and external validitywereassessedonthebasisofthesescoresbyusing product-moment correlations andunivariate ANOVA-based mean-groupcomparisons usingBonferroni corrections.For allthetestsconducted,bilateralstatisticalsignificancewas setatp≤.05.

Results

SMD-Q-9itemdescriptiveandfactoranalysis

Item means ranged from 2.59 (item 8) to 3.81 (item 1) and themean sumof SDM-Q-9 was3.15 (SD=0.9).Ingen- eral, the item scores were negatively skewed and with highkurtosisvalues.So,wedecidedtousetheunderlying- variablesapproach,andﬁttheFAmodelstotheinter-item polychoriccorrelation matrix(moredetailsin(Ferrando&

Lorenzo-Seva, 2013). This approachis quite feasible here

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making Table2 Descriptiveandfactoranalysisresults(bifactorsolution)ofSharedDecision-MakingQuestionnaire(SDM-Q-9).

Questions M SD GeneralFactor GroupFactor

1 Mydoctormadeitclearthatadecisionmustbemade. 3.81 0.6 .27 .87 2 MydoctorwantedtoknowexactlyhowIwanttobe

involvedinmakingthedecision.

3.50 0.9 .51 .54

3 Mydoctortoldmethattherearedifferentoptionsfor treatingmycondition.

3.22 1.2 .62 .49

4 Mydoctorpreciselyexplainedtheadvantagesand disadvantagesofthetreatmentoptions.

3.39 1.1 .56 .62

5 Mydoctorhelpedmeunderstandalltheinformation. 3.69 0.7 .37 .79

6 MydoctoraskedmewhichtreatmentoptionIprefer. 2.62 1.5 .91 7 MydoctorandIweighedthedifferenttreatmentoptions

thoroughly.

2.62 1.5 .98

8 MydoctorandIselectedatreatmentoptiontogether. 2.59 1.5 .98 9 MydoctorandIcametoanagreementonhowtoproceed. 3.02 1.4 .79

Note.M:mean,SD:standarddeviation.Scorerangesfrom0(stronglydisagree)to5(stronglyagree).Loadingslowerthanabsolute.25 wereomitted.

giventhatthetestisshortandthesamplereasonablylarge.

Finally,regardingmodeladequacy,theKMOindex(.87)sug- gestedthattheinter-itemcorrelationsweresubstantialand appropriateforbeingfactoranalyzed.Table2presentsthe descriptivestatisticscorrespondingtotheSDM-Q-9items.

Becauseaclearﬁnalstructurewasattainedintheentire sample,onlyasummaryofthepreviousexploratoryresults willbeprovidedhere. Theunidimensionalmodelwiththe original9itemswasuntenablebyallthestandards.Omitting item1considerablyimprovedtheﬁtbringingittothelower limitsofacceptabilityandprovidinganECVestimateof.80, whichmeansthat80%ofthecommonvarianceoftheitem scorescanbeexplainedbyageneralfactor.

Thesolutionintwofactorshadanexcellentﬁtandwas interpretable:factor 1clusteredtheitems1, 2,3,4,and 5thatassesstheinformationandexplanationsprovidedto thepatientbythephysicianabouttreatmentandtheadvan- tagesanddisadvantagesofthedifferentoptions.Factor2 clusteredtheitems6,7,8,and9thatappraisethechoiceof thebesttreatmentoption forthepatient.However,items 1and9werefactoriallycomplex,withsubstantialloadings onbothfactors.Factor1wasstrongerandbetterdeﬁned, withareplicabilityHindexof.82(Ferrando&Lorenzo-Seva, 2017) whereas that of factor 2 wasonly .75. Finally, the estimatedinter-factorcorrelationwasratherhigh:r=.61.

To sum up, the initial analyses suggest that a unidimensional solution omitting item 1 is almost acceptable, whereas thebidimensional solution ﬁtsvery well and has a clear interpretation, although it consists of two short and highly correlated factors, one of which is relatively weak, withlow replicability.Consequently, nohighlyreli- ablescorescanbeexpectedtobederivedfromthisfactor.

Inviewoftheseresultsweconsideredthatthemostappro- priateandparsimonioussolutionfortheSDM-Q-9itemswasa bifactorsolution(Rodriguez,Reise,&Haviland,2016)based onall9items,withageneralfactorthatdescribestheentire SDM process, and a group factor deﬁned by items 1 to 5 relatedtotheinformationandtreatmentoptionsprovided to the patient. The bifactor solution is justiﬁable, given thedata’sessentialunidimensionality;italsomaintainsthe parsimony and strength advantages of the unidimensional

solution(clearinterpretationandhighreliabilityofthegen- eralfactor). At the same time,the additional inter-item covariancebetweenitems1to5thatcannotbeexplained bythegeneralfactorismodeledasagroupfactor,thereby avoidingpotentialbiasonthegeneralfactorduetounmod- eledinter-itemcovariance.

Factoranalysissolution

OnthebasisoftheEFAresultssummarizedabove,abifactor SCFAsolutionwasfittedtotheentiresampledatawiththe followingspecifications: factor 1(the general factor) was definedbyall9items,andfactor 2(thegroupfactor)was definedbyitems1to5.AsinthepreviousEFAs,thebifactor modelwasfitted byusingrobustULSestimationasimple- mentedinFACTOR.Goodness-of-fitresultsareinTable3and indicateanexcellentfit.

ThegeneralfactorinTable3iswelldefinedbythe9items withallloadings>.30exceptforitem1(asexpectedfrom previousresults).Theseloadingscanbeinterpretedasitem discriminationsandarereasonablyacceptableforaperson- alitymeasure.TheH-index istherefore ratherhigh:0.88, meaningthatthefactorisstrong,welldefined,andlikelyto replicateacrossdifferentsamples.Thesecondgroupfactor ismainlydefinedbyitems1and5,whichhavehighloadings onitandonlymoderateloadingsonthegeneral.Inthiscase, theH-indexisonly 0.73,whichmeansthatthegroup fac- torisfarweakerthanthegeneralfactor,themostcommon resultinbifactorsolutions(Rodriguezetal.,2016).

Toassesstheinvarianceofthesolutiondescribedthusfar, aseriesofanalyseswereperformedbysplittingtheentire sampleintosubsamplesaccordingtogenderandpathology type.Inallcases,theresultswerefoundtobeessentially invariant, both in terms of item locations and item dis- criminations.Thus,thereappearstobenodifferentialitem functioningforanyoftheitemsandthescaleisexpectedto functionwiththesamepropertiesinthegeneralpopulation for which it is intended. Given thespace limitations, the invarianceresultsarenotprovidedhere,butareavailable fromtheauthors.

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making Table3 Robustgoodnessofﬁtstatistics.

Descriptiveﬁtindices BCBoostrap95%conﬁdenceinterval

Lower Upper

RootMeanSquareErrorofApproximation(RMSEA) .03 .00 .05

RootMeanSquareofResiduals(RMSR) .03 .02 .050

ComparativeFitIndex(CFI) .99 .99 1.00

GoodnessofFitIndex(GFI) .99 .99 1.00

Note.Cutoffcriteria:RMSEA≤.06,CFIandGFI>.95andRMSR≤.08.

Scoringandreliability

The clear bifactor solution discussed above allows two summedscorestobeobtained.Firstisthesumofthescores for all 9 items, which represents the general factor, and so,aims to measure a general dimension of perspectives regardingthedecision-makingprocesses.Thesecondscore isthesumofitems1to5,representsthegroupfactorabove, andmeasuresamorespeciﬁcsub-dimensionofinformation andtreatmentoptionsprovidedtothepatient.FromtheH resultsaboveandalsofrombasicpsychometric principles, thetotalsumscoreisexpectedtobemorereliablethanthe groupsumscore,andthiswasindeedthecase.Theomega reliabilityestimateswere.90forthetotalscoresand.85for thegroupscores.So,bothscoresachieveaquiteacceptable degreeofaccuracy,andthetotalscoresinparticularwould beconsidered as accurateenough for clinical (individual) assessment.Overall,thetotalscoresaremorerepresenta- tiveoftheentireSDMprocessandwillbetheonesusedin thevalidityassessmentsbelow.

To ascertain whetherthe reliabilityof thetotal scores reﬂectsaccuracyatalltraitlevels,conditionalreliabilities werealsoestimated(seeFerrando& Lorenzo-Seva,2017).

Resultsrevealedthatconditionalreliabilitieswere>.85for a range of trait values between two standard deviations below the mean and two standard deviations above the mean.Hence,notonlydotheSDMscorespossessgoodover- allreliability,butthisreliabilityisalsohighforalmostthe entireeffectivetraitrange,andthe.90estimatereported aboveisthusrepresentativeoftheoverallprecisionofthese scores. This resultis a positive featureof the instrument andsuggeststhatSDMwouldenablemostrespondentstobe accuratelyassessed.

Finally,giventheresultssummarizedinthissection,and forthebeneﬁtofpractitioners,anormativetablebasedon the total sum scorewas constructed based on the entire sampledata.Thetableisprovidedassupplementarymate- rial.

Constructvalidity

Constructvaliditywasexplored byanalyzing the product- moment correlations between the total SMD-Q-9 scores (as proxies for the general SDM dimension) and scores fromotherquestionnairesaimedatmeasuringtheoretically- linkeddimensions.ResultsindicatedthatthetotalSMD-Q-9 score relates positively with satisfaction regarding the patient-physician relationship (r=.29, p<.001), speciﬁcally

with the time dedicated (r=.40, p<.001), but not with theinformationprovided(r=-.02,p=.313). Similarresults werefound withthe groupfactor SDM-Q-9,which related positivelywithsatisfactionregardingthepatient-physician relationship (r=.36, p<.001) and time dedicated (r=.32, p<.001),butnotwithinformationprovided(r=.07,p=.313).

Signiﬁcant correlations were found between SDM-Q-9, patient version,and SDM-Q-Doc, physicianversion (r=.14, p<.001),betweenwomen(r=.21,p<.001),butnotinmen(r=

-.04,p=.464)andestimatedriskofrelapse(r=.04,p=.289).

Gender,ageandSDM-Q-9

Men tended to exhibit greater satisfaction with the SDM than women (F(1,566) =10.96,p<.001)and patients over 60 years(n=288)morethanyoungerones(n=270)(F(1,556)=5.19, p=.023)withsignificantintergroupdifferences(F(3,552)=7.53, p<.001). Furthermore,thesubsequentpost-hocBonferroni analysisuncoveredsignificantgender-andage-baseddiffer- ences(p<.005)suchthatwomenundertheageof60years weretheleastsatisfiedgroupwithSDMversus menofthe sameage,orolderwomen(seeFigure1).

Discussion

Theaimofthepresentstudywastoanalyzethepsychomet- ricpropertiesofSMD-Q-9createdbyKristonetal.(2010)in apopulationofpatientswithresected,non-metastaticcan- cerandinthecontextofpotentiallycurabledisease.Tothe

3.53

2.85

3.29 3.25

2 2.4 2.8 3.2 3.6 4

Women ≥60y Men ≥60y

Women <60y Men <60y

SDM-Q-9 Mean score

Figure1 Mean9-itemSharedDecision-MakingQuestionnaire (SDM-Q-9)scoresbygenderandage.

Note.Horizontally,theﬁgureshowspatientsgroupedbygender (manorwoman)andbyage(≥or<60years)andvertically,the scoreontheSharedDecision-MakingQuestionnaire(SDM-Q-9).

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making bestofourknowledge,thisistheﬁrstreportoftheSMD-Q-

9’spsychometricpropertiesinoncology,and,inthistypeof population,itshowedseveralpositiveproperties.Firstthe obtainedfactorialstructurewasclearandmeaningful,with astrongandreplicable generalfactorandamorespecific groupfactorthatcanbeofinterestinfinergradedclinical assessment. The present results arecompatiblewith previous results reported by Kriston etal. (2010) and Delas Cuevas etal. (2015), in thatthe scale wasconsidered as essentiallyunidimensional.Inlinewiththesepreviousstud- ies,we also finditem1 (Mydoctor made it clear that a decisionmustbemade)tobethemostproblematic,with lowdiscriminatingpowerandhighspecificity.Second,sum- scores derived from the factor solution, especially those correspondingto the general factor were quite accurate, withanomegaestimate.90,inlinewithpreviousreported reliabilities.

Validityresultswerelessstrong.Convergentvaliditywas explored by comparing it to the SDM-Q-Doc and Satisfac- tionwiththeInformation(SIS).Onlyaweakandstatistically signiﬁcant correlation was found between SDM-Q patient version and physicianversion. Correlations between SDM- Q-9andSISwerepositiveandsigniﬁcant,butonlyinsofaras thetimededicatedtoinformingwasconcerned,butnotwith theinformationprovided.Thus,thehypothesisofasubstan- tialcorrelationbetweentheavailabilityoftwoinstruments --- theSDM-Q-9(Kristonetal.,2010)andSDM-Q-Doc(Scholl etal.,2012),comparingthepatient’sandphysician’sper- spectivesontheSDMprocess---hasbeenslightlyestablished.

Patientsseem toexpectmoreinformationfromtheirdoc- tors.

Overall,thepsychometricresultsofourstudywerecon- sistentwiththeresultsfromtheoriginalGermanscales,as well asthe DutchandSpanishversions. Differencesmight beexplainedby factorssuchasthe scale’sceilingeffect, patients’age andgender, andtypeofcare. Asmentioned above,itemscores werenegatively skewed, whichmeans that thefull scale hasa ceilingeffect.The use of theFA based onpolychoric correlations wasexpected tocorrect forthisproblemasfarasassessmentoffactorialstructure wasconcerned.However,thereducedvarianceduetothe endeffectcanbeexpectedtoattenuateboththereliabil- ityandthevalidityestimatesbasedonthesumscores.The ceilingeffectmightbecausedbysocialdesirability(Mead&

Bower,2000)andthepatient’swishtopleasethephysician that typically occurswhen measuringpatient satisfaction (Chewningetal.,2012).SimilarresultswerefoundbyScholl et al. (2015) who found weak correlations between SDM- Q-9andOPTIONscales.Bothinstrumentsassessbehavioral aspectsofthedecision-makingprocess.Moreover,itshould bealsonotedthatinourstudy,thequestionnaireswerepro- videdaftertheinitialvisittotheoncologistandcompleted immediatelyafterward.Thiscouldincreasethesocialdesir- abilitybiasandmustbetakenintoaccountforrecruitment infutureresearch.

Oursampleconsistedofrelativelyolderpatients(mean age of 59 years)compared tothe samples in the Spanish validation study (mean age, 45 years). Older people are oftenmore satisﬁedwiththe informationprovidedby the physicianandhavelessexpectationssurroundingtheirpar- ticipationinSDM(Singh,Butow,Charles,&Tattersall,2010).

Our sample also presents a marginally higher percentage

ofwomen (59.5%),similar totheDutch sample (60%)and slightlylowerthantheSpanishvalidationone(70%).Previ- ousstudieshavefoundthatfemalecancerpatientsaremore likelytopreferSDMthanmales(Olson&Windish,2010;Singh etal.,2010),anddemandtoparticipateintheprocessmore thantheircounterparts.

Somestudiessuggestthatresponsepatternsmaydiffer dependingonage,gender,andmedicalcondition(O’Connor etal.,2009).The factthatoursampleconsistedsolelyof oncologicalpatients mayhave contributedsigniﬁcantly to thedifferencesdetected.Thegrowingcomplexityofadju- vanttherapiesusedinthetreatmentofcancercomplicates SDMasitpertainstothebesttreatmentandaddsprognos- ticuncertainty and fearto the negativeconsequences of inappropriatedecisions(Thorne,Oliffe,&Stajduhar,2016).

Futureresearchconcerningtheconstructvalidationandpre- dictivevalidityofthescaleareneeded,includingdifferent subtypesofcancerandatdifferentstages.

Finally,theSDM-Q-9maynotcaptureaspectsofthevisit, suchascommunicationstyle,bodylanguage,orempathy,all ofwhichcorrelatehighlywithsatisfaction.

Thisstudypresentscertainlimitationsthatmustbetaken intoaccountforfutureresearch.Firstofall,althoughour samplesizeislarge,participantswerepatientswithalocal- izedtumorwhohadundergonesurgeryandwerecandidates foradjuvantchemotherapy.Inthefuture,wewouldadvise expanding the sample to include other tumor stages and typeswiththe aimof confirmingthese results,aswell as tocomparedifferentclinical-pathologicalandsocialvaria- bles.Secondly,theSDM-Q-9self-reportsubjectivemeasures maynotaccuratelyreflectpatients’experiences,expectations,andbehavior,havinglimitationssuchasresponsebias (socialdesirability,inaccuratememory,etc.)andtheirdiffi- cultyinfullycomprehendingtheSDMprocess(Shay&Lafata, 2015). Finally, in addition to this design, it would be fit- tingtoexplorethe dynamicnatureofSDM processeswith otherlongitudinalstudiesthatenableSDMtobeevaluated morecomprehensively,exploringitseffectsbeforeandafter adecisionismade.

In conclusion, the ‘‘Shared Decision Making Question- naire’’appliedtopatientswithcancerpossessesadequate psychometric properties, similar to those obtained by Kristonetal.(2010),Simonetal.(2006),andDelasCuevas etal. (2015). The results of this study prove that it is a validandreliable toolfor analyzing and attaininggreater insightintotheSDM process.On theother hand, knowing whichconditionshelporhinderengagementinthisdecision- makingprocesscanhelptoestablishtheclinicalconditions necessarytoenhancepatients’wellbeing.

SDMisaprocessaimedatlearningpatients’preferences andneedsandtowardempoweringthemtotakeanactive roleincaringfortheirhealthinlinewiththeirwishes.The SDM-Q-9canbeusefultoanalyzethesepatients’perspective ofthe SDMandasan indicator ofqualityand satisfaction withhealthcareservices.

Funding and acknowledgements

This work was funded by the Spanish Society of Medical Oncology (SEOM) in 2015. The sponsor of this research has not participated in data collection, analysis, or

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Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making interpretation,inwriting thereport,or inthedecision to

submitthearticle for publication.The authorswouldlike tothanktheinvestigatorsof theNeocopingstudy(coping, shareddecision-makingandqualityoflifeinpatientswith earlystagecancertreatedwithadjuvantchemotherapy)and theSupportiveCareWorkingGroupoftheSpanishSocietyof MedicalOncology(SEOM).

Sources of funding

This work was funded by the Spanish Society of Medical Oncology(SEOM)in2015.The sponsorofthisresearchhas notparticipatedindatacollection,analysis,orinterpreta- tion,inwritingthereport,orinthedecisiontosubmitthe articleforpublication.

Acknowledgements

TheauthorswouldliketothanktheinvestigatorsoftheNeo- copingstudy(coping,shareddecision-makingandqualityof lifeinpatientswithearlystagecancer treatedwithadju- vantchemotherapy)andtheSupportiveCareWorkingGroup oftheSpanishSocietyofMedicalOncology(SEOM).

References

Calderon,C.,Ferrando,P.J.,Carmona-Bayonas,A.,Lorenzo-Seva, U.,Jara,C.,Beato,C.,García,T.,Ramchandani,A.,Castelo,B., Mu˜noz,M.M.,García,S.,Higuera,O.,Mangas-Izquierdo,M.,&

Jimenez-Fonseca,P.(2017).ValidationofSDM-Q-DocQuestion- nairetomeasureshareddecision-makingphysician’sperspective inoncology practice.Clinical andTranslationalOncology,19, 1312---1319.http://dx.doi.org/10.1007/s12094-017-1671-9 Carretero-Dios,H.,&Pérez,C.(2005).Normasparaeldesarrollo

yrevisióndeestudiosinstrumentales.InternationalJournalof ClinicalandHealthPsychology,5,521---551.

Chewning,B.,Bylund,C.L.,Shah,B.,Arora,N.K.,Gueguen,J.A.,

&Makoul,G.(2012).Patientpreferencesforshareddecisions:A systematicreview.PatientEducationandCounseling,86,9---18.

http://dx.doi.org/10.1016/j.pec.2011.02.004

Coulter,A.,&Collins,A.(2011).MakingSharedDecision-Makinga Reality.London:King’sFund.

Coulter, A., Parsons, S., & Askham, J. (2008). Where are the patients in decision-making about their own care?

Health Systems. Health and Wealth, 1---26. Available from:

http://www.who.int/management/general/decisionmaking/

WhereArePatientsinDecisionMaking.pdf

De la Torre-Luque, A., Gambara, H., López, E., & Cruzado, J. A. (2016). Psychological treatments to improve quality of life in cancer contexts: A meta-analysis. International Journal of Clinical and Health Psychology, 16, 211---219.

http://dx.doi.org/10.1016/j.ijchp.2015.07.005

De las Cuevas, C., Perestelo-Perez, L., Rivero-Santana, A., Cebolla-Martí, A., Scholl, I., & Härter, M. (2015). Validation of the Spanish version of the 9-item Shared Decision- Making Questionnaire. Health Expectations, 18, 2143---2153.

http://dx.doi.org/10.1111/hex.12183

Elwyn,G.,Dehlendorf, C.,Epstein, R., Marrin,K., White,J., &

Frosch, D. (2014). Shared decision making and motivational interveiwing:Achievingpatient-centredcare acrossthespec- trumofhealthcareproblems.AnnalsofFamilyMedicine,12, 270---275.http://dx.doi.org/10.1370/afm.1615

Ferrando,P.J.,&Lorenzo-Seva,U.(2013).Unrestricteditemfac- tor analysis and somerelations with item response theory,.

Retrievedfromhttp://psico.Fcep.Urv.Es/utilitats/factor Ferrando, P. J., & Lorenzo-Seva, U. (2017). Assessing the Qual-

ity and Appropriateness ofFactor Solutions and Factor Score Estimates in Exploratory Item Factor Analysis. Educational and Psychological Measurement. AdvanceOnline Publication, http://dx.doi.org/10.1177/0013164417719308

Jönsson, B., Hofmarcher, T., Lindgren, P., & Wilking, N.

(2016). The cost and burden of cancer in the European Union 1995-2014. European Journal of Cancer, 66, 162---170.

http://dx.doi.org/10.1016/j.ejca.2016.06.022

Kriston, L.,Scholl, I., Hölzel, L.,Simon, D.,Loh, A.,& Härter, M. (2010). The 9-item Shared Decision MakingQuestionnaire (SDM-Q-9).Developmentandpsychometricpropertiesinapri- marycaresample.PatientEducationandCounseling,80,94---99.

Libert, Y., Canivet, D., Ménard, C., Van Achte, L., Far- vacques, C., Merckaert, I., Liénard, A., Klastersky, J., Reynaert, C., Slachmuylder, J. L., Durieux, J. F., Delvaux, N., & Razavi, D. (2017). Predictors of physicians’ communication performance in a decision-making encounter with a simulated advanced-stage cancer patient: A longitudinal study. Patient Education and Counseling, 100, 1672---1679.

Lorenzo-Seva, U., & Ferrando, P. J. (2013). FACTOR 9.2:

A Comprehensive Program for Fitting Exploratory and Semiconﬁrmatory Factor Analysis and IRT Models.

Applied Psychological Measurement, 37, 497---498.

http://dx.doi.org/10.1177/0146621613487794

McDonald,R.P.(1999).Testtheory:Auniﬁedtreatment.NewYork:

PsychologyPress.

Mead, N., & Bower, P. (2000). Patient-centredness: A conceptual framework and review of the empirical lit- erature. Social Science & Medicine, 51, 1087---1110.

http://www.ncbi.nlm.nih.gov/pubmed/11005395

O’Connor,A.M.,Bennett,C.L.,Stacey,D.,Barry,M.,Col,N.F., Eden,K.B.,Entwistle,V.A.,Fiset,V.,Holmes-Rovner,M.,Khan- qura,S.,Llewellyn-Thomas,H.,&Rovner,D.(2009).Decision aidsforpeoplefacinghealthtreatmentorscreeningdecisions.

TheCochrane Databaseof SystematicReviews, 3,CD001431.

http://dx.doi.org/10.1002/14651858.CD001431.pub2

Olson, D. P., & Windish, D. M. (2010). Communication discrepancies between physicians and hospitalized patients. Archives of Internal Medicine, 170, 1302---1307.

http://dx.doi.org/10.1001/archinternmed.2010.239

Ramos-Álvarez, M.M., Moreno-Fernández, M. M., Valdés-Conroy, B., & Catena, A. (2008). Criteria of the peer review process for publication of experimental and quasi-experimental researchinPsychology:Aguidefor creatingresearchpapers.

International Journal of Clinical and Health Psychology, 8, 751---764.

Rodenburg-Vandenbussche, S., Pieterse, A. H., Kroonenberg, P.

M., Scholl, I., van der Weijden, T., Luyten,G. P. M., Kruit- wagen, R. F., den Ouden, H., Carlier, I. V., van Vliet, I. M., Zitman, F. G., & Stiggelbout, A. M. (2015). Dutch Translation and Psychometric Testing of the 9-Item Shared Decision Making Questionnaire (SDM-Q-9) and Shared Deci- sion Making Questionnaire-Physician Version (SDM-Q-Doc) in Primary and Secondary Care. PLOS ONE, 10, e0132158.

http://dx.doi.org/10.1371/journal.pone.0132158

Rodriguez, A., Reise, S. P., & Haviland, M. G. (2016). Eval- uating bifactor models: Calculating and interpreting statistical indices. Psychological Methods, 21, 137---150.

http://dx.doi.org/10.1037/met0000045

(9)

Please cite this article in press as: Calderon, C., et al. Psychometric properties of the Shared Decision-Making Schermelleh-Engel,K.,Moosbrugger,H.,&Müller,H.(2003).Evalu-

atingthefitofstructuralequationmodels:Testsofsignificance anddescriptivegoodness-of-fitmeasures.MethodsofPsycholog- icalResearchOnline,8,23---74.

Scholl, I., Kriston, L., Dirmaier, J., Buchholz, A., & Härter, M. (2012). Development and psychometric properties of the Shared Decision Making Questionnaire --- physician version (SDM-Q-Doc).PatientEducationandCounseling, 88,284---290.

Scholl, I., Kriston, L., Dirmaier, J., & Härter, M. (2015).

Comparing the nine-item Shared Decision-Making Ques- tionnaire to the OPTION Scale - an attempt to establish convergent validity. Health Expectations, 18, 137---150.

http://dx.doi.org/10.1111/hex.12022

Schuler,M.,Schildmann,J.,Trautmann, F.,Hentschel,L.,Horne- mann,B.,Rentsch,A.,Ehninger,G.,&Schmitt,J.(2017).Cancer patients’control preferencesindecisionmakingand associa- tionswithpatient-reported outcomes:Aprospective studyin an outpatientcancer center.Supportive Care in Cancer, 25, 2753---2760.http://dx.doi.org/10.1007/s00520-017-3686-8 Shay, L. A., & Lafata, J. E. (2015). Where is the evidence?

A systematic review of shared decision making and patient outcomes.Medical DecisionMaking: AnInternationalJournal

of the Society for Medical Decision Making, 35, 114---131.

http://dx.doi.org/10.1177/0272989X14551638

Simon, D., Schorr, G., Wirtz, M., Vodermaier, A., Caspari, C., Neuner, B., Spies, C., Krnoes, T., Edwards, A., Loh, A., & Härter, M. (2006). Development and ﬁrst validation of the shared decision-making questionnaire (SDM-Q). Patient Education and Counseling, 63, 319---327.

Singh,S.,Butow, P., Charles,M., & Tattersall, M.H. N. (2010).

Shared decision making in oncology: Assessing oncologist behaviourinconsultationsinwhichadjuvanttherapyisconsid- eredafterprimarysurgicaltreatment.HealthExpectations,13, 244---257.http://dx.doi.org/10.1111/j.1369-7625.2009.00587.x Tamirisa, N. P., Goodwin, J. S., Kandalam, A., Linder, S. K., Weller, S., Turrubiate, S., Silva, C., & Riall, T. S. (2017).

Patient and physician views of shared decision making in cancer. Health Expectations. Advance Online Publication, http://dx.doi.org/10.1111/hex.12564

Thorne, S., Oliffe, J. L., & Stajduhar, K. I. (2016). Com- municating shared decision-making: Cancer patient perspectives. Patient Education and Counseling, 90, 291---296.