Quality issues of self-report of hypertension: Analysis of a population representative sample of older adults in Taiwan

Quality issues of self-report of hypertension: Analysis of a population representative sample of older adults in Taiwan

Alan Chung-Hong Tsai

*, Tsui-Lan Chang

aDepartmentofHealthcareAdministration,AsiaUniversity,500LiufengRd.,Wufeng,Taichung41354,Taiwan

bDepartmentofHealthServicesManagement,ChinaMedicalUniversity,91Hsueh-ShihRoad,Taichung40402,Taiwan

cNursingDepartment,HsinYungHoHospital,No.81,Sec.1,YanpingRd.,Pingzhen,Taoyuan32441,Taiwan

1. Introduction

Hypertensionisprevalentinmostindustrializedpopulations, especiallyintheelderly.Itisa chronicconditionthat canoften increasetherisk of stroke,heart disease, diabetesmellitus and chronic kidney disease, the leading causes of death in many industrialized populations (Rutan et al., 1988; Agarwal, 2005;

Barri,2006;Ganneetal.,2007).InTaiwan,morethan50%ofthe elderlyarehypertensive(Panetal.,2001;Chiuetal.,2006).Hence, surveillanceprogramsandpreventiveactivitiesaimingtoreduce theprevalenceofhypertensionareimportanttopublichealth.

Ideally,hypertensionsurveillanceshouldbedonebymeasuring blood pressure of individuals. However, because of cost and complexity, large scale surveys are conducted only rather

infrequently, and self-report is oftenused as an alternative to estimate the trend of hypertension at both national and local levels.Therefore,thevalidityofself-reportsisanimportantissue.

Self-report must be able to correctly reflect the diagnosis of hypertensionorit wouldhavelittle value.Severalstudieshave shown that self-report has a fair sensitivity and can yield a reasonableestimateoftheprevalenceofhypertensioninWestern populations(Bushetal.,1989;Kehoe etal.,1994;Martinetal., 2000; Tormo et al., 2000). However, observations made in Taiwanese are somewhat less satisfactory. The validity of self- reportofhypertensionhasbeenshowntobeaffectedbyanumber of factors including gender, age, ethnicity, level of education, whetheronehashadarecenthealthcheck-upandthewillingness toreveal personalhealth status (Tormoetal., 2000;Wu et al., 2000;Goldmanetal.,2003).

Thedifference intheaccuracy ofself-reportofhypertension between theWestern populationsand the Taiwanese (anewly industrializedpopulation)deservefurtherinvestigation.Although population-relatedcultural (socioeconomicand lifestyle) differ- encesareimportant,webelievethatthevariationinhealthcare ARTICLE INFO

Articlehistory:

Received14August2011

Receivedinrevisedform14September2011 Accepted15September2011

Availableonline11October2011

Keywords:

Bloodpressure Hypertension Self-report Taiwan

ABSTRACT

Thestudywastoevaluatethequalityofself-reportofhypertensionandexaminethefactorsassociated withunder-andover-reportingofhypertensioninolderTaiwanese.Dataforthisanalysiswerefromthe SocialEnvironmentandBiomarkersStudyinTaiwan2000,whichinvolvedanationalsampleof1021 Taiwaneseover54yearsofage.Weperformedbinaryclassificationteststocomparetheprevalencerates ofself-reportedvs.clinicallymeasuredhypertensionaccordingtoWorldHealthOrganization(WHO) (blood pressure160/95mmHg oron hypertension medication) and JNC-6(140/90mmHg or on hypertension medication) definitions. Logistic regression analysis was performed to analyze the potentialfactorsassociatedwithunder-orover-reportingofbloodpressurestatus.Resultsshowedthe testcharacteristicsofself-reportswere:sensitivity73%,specificity93%,andkappa=0.68(p<0.001) basedontheWHOdefinition;andsensitivity51%,specificity95%andkappa=0.43(p<0.001)basedon theJNC-6definition.Oldagewasassociatedwithover-reportingwhereashavingnohealthcheckup duringthepast12monthswasassociatedwithunder-reporting.Therelativelylowagreementbetween self-reportsandclinicallymeasuredhypertension(JNC-6definition)wasmainlyduetothelackofawell- definedhypertensionpracticeguidelineandthefailureofclinicianstoclearlyinformpatientsoftheir diagnoses.Theconsistencyofhypertensionpracticeguidelinesandtheeffectivenessofinformingthe patientsoftheirdiagnosesaretwomainfactorsimpactingthequalityofself-reportofhypertensionin elderly Taiwanese. Better self-reports of health data can improve the efficiency of public health surveillanceefforts.

ß2011ElsevierIrelandLtd.Allrightsreserved.

*Corresponding author at: Department of Healthcare Administration, Asia University,500LiufengRd.,Wufeng,Taichung41354,Taiwan.

Tel.:+886423323456x1943;fax:+886423321206.

E-mailaddress:atsai@umich.edu(A.-H.Tsai).

ContentslistsavailableatSciVerseScienceDirect

Archives of Gerontology and Geriatrics

j ou rna l h om e pa ge : w w w. e l s e v i e r. co m/ l oc a t e / a rch ge r

0167-4943/$–seefrontmatterß2011ElsevierIrelandLtd.Allrightsreserved.

doi:10.1016/j.archger.2011.09.009

systemsanddailyclinicalpractice(suchasthewaypatientsare informedoftheirdiagnosis)alsoplayarole.Thus,theobjectivesof thepresentstudyweretoevaluatethequalityofself-reportof hypertension and to explore the factors associated with the accuracyofself-reportofhypertensioninelderlyTaiwanese.

2. Methods

2.1. Designandsubjects

Data used in this report were from the SEBAS (Social EnvironmentandBiomarkers StudyinTaiwan,2000, Weinstein and Goldman, 2006). The SEBASwas a sub-sampleof a larger cohortstudyentitled‘‘SurveyofHealthandLivingStatusofthe ElderlyinTaiwan’’(SHLSET)whichwasinitiatedin1989witha population-representativesampleof4049personsaged60years orolder(Hermalinetal.,1989).In1996,thesamplewasextended toinclude2462near-elderlypersonsaged50–66years(Changand Hermalin, 1996a,b). The SEBAS study was drawn from this combinedcohortin2000.BothSHLSETandSEBASwereconducted bytheBureauofHealthPromotionoftheDepartmentofHealthof Taiwan and the protocols were reviewed and approved by government-appointed representatives. The studies were con- ductedaccordingtotheethicalstandardssetforthintheHelsinki Declaration.

2.2. Measurements

Among 4400 subjects in the cohort, 1713 were selected randomly. Among those selected, 1698 were contacted for interviewand1497providedinterviews.Amongrespondentsto theinitialinterview,1023participatedinthephysicalexamination and1021hadcompletedata,whichisthedatabaseusedinthe currentanalysis.Thecompositionofthesub-samplingwasshown to be not different from the parent cohort (Weinstein and Goldman,2006).

TheSEBASsurveyincludeda face-to-facein-homeinterview conductedbytrainedinterviewersandacomprehensivephysical examination.Questionsrelatedtothecurrentstudywere:‘‘Doyou everhaveorcurrentlyhavehighbloodpressure?’’and‘‘Areyou taking anti-hypertensive medicine?’’ The questionnaire used simpletalkingChinesefortheseconditionsandwasadministered accordingtorespondent’sdialectwithoutanydescription about thenatureoftheconditions.Aspartofthephysicalexamination, registerednursestooktwobloodpressurereadings(1minapart) usinga mercury sphygmomanometer withtherespondentin a seatedpositionatleast20minaftertherespondentarrivedatthe hospital. Finally, a physician performed a medical examination includingathirdbloodpressurereading.

Inthepresentanalysis,theprevalenceratesof hypertension were estimated separately from self-reports and from the measured values. Self-reported blood pressure values were cross-tabulated with the outcome of measured results. For comparison purposes, hypertension was defined according to twodefinitions(a)theWHO-definitionatthetimeofthesurvey:

SBP/DBP(diastolicbloodpressure/diastolicbloodpressure)160/

95mmHgor takinganti-hypertensivemedication(WHO,1993) and(b)theJNC-6definition:SBP/DBP140/90mmHgortaking anti-hypertensivemedication(JNCVI,1997).

2.3. Statisticalanalysis

Binarycross-tabulationtestswereperformedtoevaluatethe significanceofdifferencesbetweenthetwomethods.Regression analyseswereperformedtodeterminethefactorsassociatedwith over-orunder-reportingofbloodpressurestatus,respectively.All

analyseswereperformedwithSPSS15.0SoftwarePackage(SPSS Inc.,Chicago,IL).Statisticalsignificancewasevaluatedat

a

3. Results

Table 1 shows the characteristics of subjects. The study included slightly more men than women which reflected the compositionof thespecificagegroup.Approximately37%were near-old(54–64years),60%were65–84yearsoldand2.4%were 85yearsorolder.Nearlyonequarter(23.6%)oftherespondents werecurrentsmokersandasimilarproportion(23%)drankalcohol atleastoncepermonth.

Table 2 shows thecross tabulation analysis of self-reported bloodpressurestatusandmeasuredbloodpressurebasedonthe WHO (BP160/95mmHg) and JNC-6 (BP140/90mmHg) criteria,respectively.Thetestcharacteristicsofself-reportsusing BP160/95mmHgasareferencewere:sensitivity73%,specificity 93% and kappa=0.68(p<0.001). The testcharacteristics using JNC-6 definition were: sensitivity 51%, specificity 95% and kappa=0.43(p<0.001).UsingtheWHOdefinitionasareference, 44elderlyover-reportedand104under-reported;usingJNC-6asa reference,23over-reportedand285under-reported.

Table3showstheoutcomeoflogisticregressionanalysisofthe associationofvariousvariables withover- orunder-reportinga bloodpressurestatus.Amongvariablesexamined,oldagewasthe onlyvariableshowntobeassociatedwithover-reportingwhereas havingaphysicalcheck-upduringthelast12monthswastheonly variable associatedwithunder-reportingbasedon theWHO or JNC-6definition.

Table1

Characteristicsofsubjects(n=1021).

Variables n(%)

Sex

Men 589(57.7)

Women 432(42.3)

Age,years

54–64 382(37.4)

65–74 372(36.4)

75–84 242(23.7)

85 25(2.4)

Formaleducation,years

6 753(73.8)

7 268(26.2)

Currentsmokers

No 779(72.3)

Yes 242(23.7)

Drinkalcohol(1time/month)

No 783(76.7)

Yes 238(23.3)

Table2

Crosstabulation ofself-reportedhypertensionagainstmeasuredhypertension accordingtotwohypertensiondefinitions.

Self-reported MeasuredSBP/DBP^a

WHOdefinition JNC-6definition

Hypertension^b Yes No Yes No

Yes 281 44 302 23

No 104 592 285 411

Sensitivity 0.73 0.51

Specificity 0.93 0.95

PPV^c 0.86 0.93

NPV^c 0.85 0.59

Kappa 0.68 0.43

a WHOdefinitionis160/95mmHgoronanti-hypertensivemedication,and JNC-6is140/90mmHgoronanti-hypertensivemedication.

b Self-reportedhypertensionoronanti-hypertensivemedication.

cPPV,positivepredictivevalue;NPV,negativepredictivevalue

Table4liststhemajoreventsrelatedtotheestablishmentofan officialcriterionforhypertensioninTaiwan.

4. Discussion

4.1. Self-reportedvs.measuredvalues

The prevalence rate of clinically measured hypertension amongelderlyTaiwaneseis37.7%basedontheWHOdefinition (BP160/95mmHg) and 57.5% based on JNC-6 definition (BP140/90mmHg) whereas the prevalence rate is 31.8%

basedon self-report. Self-report is relatively good (sensitivity 73%,specificity 95%andkappa=0.68)atconfirminghyperten- sion against clinically measured outcome based onthe WHO definition,andtheresultiscomparabletothatobservedinthe USandotherWesterncountries(Bushetal.,1989;Kehoeetal., 1994; Martin et al., 2000; Tormo et al., 2000). Vargas et al.

(1997) analyzed the NHANES-III (National Health and Nutri- tionalExaminationSurveyIII, 1988–1991)data andfoundthe test characteristics of self-reports were: sensitivity 71% and specificity 90% amongadults 25–74years old basedon JNC-6 criteria. In a smaller scale study comparing self-reports of a random sample of health maintenance organization (HMO) subscribers in Colorado with HMO medical records, the test characteristicsof self-reportswere: sensitivity81%andspeci- ficity73%forpatients65yearsofageorolderbasedonJNC-6 criteria(Martinet al.,2000).

However, the present study shows that self-report under- predicted hypertension by a relatively large margin against

clinically measured values based on the JNC-6 definition (BP140/90mmHg).Thetestcharacteristicsofself-reportswere sensitivity51%,specificity95%andkappa0.43.Theseresultsarein linewiththatobservedbyWuetal.(2000)whoshowedsensitivity 49%,specificity 83%and kappa=0.33basedon JNC-6definition (BP140/90mmHg)inastudyinvolving228elderlyTaiwanese in1992–1993.Goldmanetal.(2003)analyzedself-reportofthe SEBASdataagainstclinicallymeasured hypertensionandfound 49%sensitivity,95%specificityandkappa=0.41basedonJNC-6 definition(BP140/90mmHg).Goldmanetal.(2003)attributed the low reliability of self-report of hypertension by elderly TaiwanesetoanumberoffactorssuchasthetraditionalChinese beliefsabouthypertension,lowlevelsofbloodpressurescreening, failureofclinicianstocommunicatediagnosiswithpatientsand poor recall by respondents. While we agree that those are contributoryfactors,webelievethatthereareotherfactorsunique totheTaiwanesethatcausethebias.

4.2. Reasonsforunder-reporting

Ouranalysessuggestthatthereliabilityofself-reportismuch dependentonthereferencevaluesuggestingthatthedifferencesin practiceguidelinesusedbythecliniciansisacontributingfactorto thelow reliabilityof self-reportof hypertensionin thecurrent studywhentestedagainstJNC-6criteria.

Inprinciple,thereferencevalueshouldbethedefinedcriterion ofhypertensioninthepracticeguidelineatthetimeofthesurvey.

However,TaiwanwasintransitionatthetimeoftheSEBASstudy.

Therewasnotanofficiallydefinedcriterion(orpracticeguideline) forhypertensionuntil1996whentheDepartmentofHealth(DOH) of Taiwanissued ‘‘The HypertensionPrevention and Treatment Manual’’forthefirsttime(Dept.ofHealth,Taiwan,1996).Thisfirst manual described both the WHO (1993) and the JNC-6(1997) definitions but did not clearly specify an official definitionfor Taiwanese.Onlyby2004,theDOHpublishedthefirstrevisionof theManualandofficiallyadoptedtheJNC-7(BP140/90mmHg, samethresholdsastheJNC-6)criteria(JNCJII,2003)astheofficial definitionforTaiwanese(BureauofHealthPromotionoftheDept.

of Health, Taiwan, and Taiwan Internal Medicine Association, 2004).Thus,atthetimeoftheSEBASsurvey(2000),thecriterion forhypertensionwasnotofficiallydefinedanditwasprettymuch left to the clinicians. A recent survey by us showed that the threshold for hypertension used by practicing nurses and physicians in CentralTaiwan before2004 rangedfromBP 130/

80to160/110mmHg(unpublishedobservation).

Withoutasetofwell-definedpracticeguideline,theclinicians couldnothaveadoptedauniformdefinition,andasaresultthe patientswouldnotbeabletoproducethecorrectrecallsofthe Table3

Logisticregressionanalysisofthefactorspotentiallyassociatedwithover-orunder-reportingofself-reportofhypertensionin54yearsTaiwanese.

Variables %Total WHO(160/95mmHg) JNC-6definition(140/90mmHg)

Over(44)^a Under(104)^a Over(23)^a Under(285)^a

%Case OR(95%CI) %Case OR(95%CI) %Case OR(95%CI) %Case OR(95%CI)

Age,years

54–64 382(37.4) 13(3.4) 1 35(9.2) 1 9(2.4) 1 95(24.9) 1

65–74 372(36.4) 16(4.3) 1.93(0.87–4.28) 38(10.2) 0.86(0.48–1.53) 4(1.1) 0.85(0.24–3.00) 110(29.6) 0.81(0.53–1.24)

75 267(26.2) 15(5.6) 2.43(1.07–5.51)^* 31(11.6) 1.06(0.57–1.98) 10(3.7) 2.78(1.00–7.75)^* 80(30.0) 0.91(0.60–1.45) Healthexampast12-m

No 665(65.1) 26(3.9) 1 79(11.9) 1 16(2.4) 1 209(31.4) 1

Yes 356(34.9) 18(5.1) 1.39(0.74–2.64) 25(7.0) 0.53(0.31–0.91)^* 7(2.0) 0.86(0.31–2.21) 76(21.3) 0.57(0.40–0.82)^*

Numberofobservations 636 385 434 587

Notes:Allregressionmodelsareadjustedforgender,yearsofeducation,ethnicity,livinglocationandlifestylefactors(smoking,drinkingandphysicalactivity).

*Significantlydifferentfromthereferencegroup(p<0.05).

aBasedonWHOdefinition,44ofthe636whowerenormotensiveover-reportedand104of385whowerehypertensiveunder-reported;basedJNC-6definition,23of434 whowerenormotensiveover-reportedand285of587whowerehypertensiveunder-reported.

Table4

HistoryofhypertensiondefinitionchangesinTaiwan.

Year Event

1993 WHOpublishedthe‘‘1993Guidelinesforthemanagementof mildhypertension’’anddefinedhypertensionasBP160/95mmHg 1996 TheDept.ofHealthofTaiwanpublishedthefirsteditionof

‘‘HypertensionPrevention&TreatmentManual’’anddefined hypertensionperWHO(BP160/95mmHg)definitionbutalso discussedtheJNC-5(140/90mmHg)criteria

1997 JNCpublishedJNC-6(BP140/90mmHg)definition 2003 JNCpublishedJNC-7(BP140/90mmHg)definition

2004 Dept.ofHealthofTaiwanrevisedthe‘‘HypertensionPrevention

&TreatmentManual’’andadoptedtheJNC-7(BP140/90mmHg) definition

2005 TaiwanMedicalAssociationadoptedJNC-7definition

Notes:WHO/ISH,WorldHealthOrganization,InternationalSocietyofHyperten- sion;JNC,Joint NationalCommitteeonprevention, detection,evaluation,and treatmentofhighbloodpressure;NationalHighBloodPressureEducationProgram CoordinatingCommittee;BP,bloodpressure.

diagnoses. Our survey also shows that many clinicians do not informthediagnosistotheirpatients forcefullyandunambigu- ously.Inmanycases,subjectsareonlygentlyinformedthathis/her blood pressure is ‘‘a bithigh’’ withoutclearly telling theexact valuesorwhetheritexceedsasetstandard.So,manypatientsmay thinkthathis/herbloodpressureisonlyslightlyhigh,notenough tobe classifiedhypertensive. Results showthat many subjects being classified hypertensive only because they are on anti- hypertensionmedication.Thus,unlesspatientsarecorrectlyand unambiguouslyinformedoftheirbloodpressurediagnoses,they arelikelytounder-reporttheirhypertensionstatus.

4.3. Variablesassociatedwithunder-orover-reporting

Thepresentstudyalsoshowthataccordingtotheregression models,thosewhoare65yearsorolder(comparedtoyoungerold, 54–65y) are more likely toover-report hypertensionbased on either the WHO (BP160/95mmHg)or the JNC-6 (BP140/

90mmHg) definition. This finding is consistent with the observationof Wu etal.(2000).The exactreason fortheover- reportingis not known but may bein part due toage-related memory or cognitive impairment and the undetected old age- relatedbloodpressuredecline.Bloodpressuregenerallyreachesa peakaround75yearsoldforsystolicpressureandaround60years old for diastolic pressure and then declines (Dept. of Health, Taiwan,1996).Itispossiblethatsomeolderindividualsremember earlierdiagnosisbutdonotknowtherecentchanges.Resultsalso showthathavingahealthexaminationduringthepast12-month significantly reduces theprobability ofunder-reporting, as was observedbyGoldmanetal.(2003).

Self-reportsupposedlyreflectstherecallofrecentlymeasured blood pressure status. However, the accuracy of self-report is dependentnotonlyonthesubject’sabilitytorecallitcorrectlybut also the subjects to maintain the same blood pressure status.

Further, blood pressure normally fluctuates considerably in hypertensive and non-hypertensive individuals. In the elderly, changes in health condition and medication aggravate the fluctuations.

4.4. Limitations

Therearelimitationstothisstudy.(a)SubjectsoftheSEBAS study,a sub-samplingoflongitudinalcohortstudy,haveunder- gonepersonalinterviewsevery3–4yearssincethebeginningof theproject in1989.Itispossiblethatthesesubjectshavebeen

‘‘educated’’morethantheaveragecitizensabouthealthissues.(b) Althoughfreeannualhealthcheck-upwasavailabletothosewho were65 years or older through the NationalHealth Insurance Program, participation was voluntary and is not consistent throughoutallelderlyagerangesandthatmayaffecttheoutcome ofself-report.(c)Asmentionedearlier,Taiwanwasintransitionin defininghypertension,cliniciansseemedtohavedefinedhyper- tensiondifferentlyandthatwillalsoaffecttheaccuracy ofself- report.

5. Conclusions

Resultsofthepresentstudysuggestthatthereliabilityofself- reportofhypertensionismuchdependentonhavingthecorrect reference standard (practice guidelines). Clinicians should be instructedtoadheretotheofficialdefinitionofmedicalconditions andclearlyinformpatientsoftheirdiagnoses.Thesefindingsare usefulforimprovingtheresultofself-reportofhypertensionwhich is often a part of health surveys. Accurate survey results are essential for making proper public health policies. Knowledge

learned from this analysis shouldbe applicableto many other countriesaimingtoimprovehypertensionsurveillance.

Conflictofintereststatement None.

Acknowledgements

The authorswish tothank theBureauof Health Promotion, DepartmentofHealthofTaiwanforprovidingthedatasetforthe presentstudy.Descriptionsorconclusionshereindonotrepresent theviewpointoftheBureau.Thestudyissupportedbyagrantfrom theNationalScienceCouncilofTaiwan(NSC97-2320-B-468-003).

Thestudyreceivednowritingassistanceinthepreparationofthis manuscript.

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