www.jped.com.br
ORIGINAL
ARTICLE
Performance
of
different
diagnostic
criteria
of
overweight
and
obesity
as
predictors
of
metabolic
syndrome
in
adolescents
夽
Raphael
Gonc
¸alves
de
Oliveira,
Dartagnan
Pinto
Guedes
∗UniversidadeNortedoParaná(Unopar),CentrodePesquisaemCiênciasdaSaúde,Londrina,PR,Brazil
Received22July2016;accepted25November2016 Availableonline30May2017
KEYWORDS
Bodymassindex; Diagnosis; Accuracy;
Cardiovascularrisk; Youth
Abstract
Objective: Toanalyzetheperformanceofthreedifferentdiagnosticcriteriaofoverweightand obesity (WHO,IOTF andConde andMonteiro) usingbody massindex(BMI) aspredictors of metabolicsyndrome(MetS)inarepresentativesampleofadolescents.
Methods: Asampleof1035adolescentsaged12---20years(565girlsand470boys)wasusedin thestudy.BMIwas calculatedthroughthequotientofweight (kg)/heightsquared(m)2,and
MetSwasdefinedaccordingtothecriteriaoftheInternationalDiabetesFederation.Sensitivity, specificity, andoverall accuracy (area under thecurve) were estimated using the receiver operatingcharacteristic(ROC)curvesmethodandusedtodescribethepredictiveperformance.
Results: Thethreediagnosticcriteriashowedhigherabsolutevaluesofsensitivityand speci-ficityforpredictingMetSinboysandolderadolescents.ThehighestsensitivitytoidentifyMetS was found usingtheIOTFcriterion (60---85%),whilespecificityvalues≥90% werefound for thethreecriteria.TheCondeandMonteirodiagnosticcriterionpointedtoasignificantlylower overallaccuracy(0.52---0.64)thanthatoftheWHO(0.70---0.84)andIOTF(0.75---0.89)diagnostic criterion.
Conclusions: Overweight and obesity using BMI showed a moderate association with MetS, regardlessofthediagnosticcriteriaused.However,theIOTFcriterionshowedbetterpredictive capacityforthepresenceofMetSthantheWHOandtheCondeandMonteirocriteria. ©2017SociedadeBrasileiradePediatria.PublishedbyElsevierEditoraLtda.Thisisanopen accessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/ 4.0/).
夽
Pleasecitethisarticleas:OliveiraRG,GuedesDP.Performanceofdifferentdiagnosticcriteriaofoverweightandobesityaspredictors ofmetabolicsyndromeinadolescents.JPediatr(RioJ).2017;93:525---31.
∗Correspondingauthor.
E-mail:[email protected](D.P.Guedes).
http://dx.doi.org/10.1016/j.jped.2016.11.014
PALAVRAS-CHAVE
Índicedemassa corporal; Diagnóstico; Acurácia;
Riscocardiovascular; Jovens
Desempenhodediferentescritériosdiagnósticosdesobrepesoeobesidadecomo
preditoresdesíndromemetabólicaemadolescentes
Resumo
Objetivo: Analisarodesempenhodetrêsdiferentescritériosdiagnósticosdesobrepesoe obesi-dade(WHO,IOTFeConde&Monteiro)apartirdoíndicedemassacorporal(IMC)comopreditores dasíndromemetabólica(SMet)emamostrarepresentativadeadolescentes.
Métodos: Aamostrafoiconstituídapor1035adolescentes(565moc¸ase470rapazes)comidades entre12e20anos.OIMCfoicalculadomediantequocienteentrepeso(kg)/altura(m)2eSMet
foidefinidaatravésdoscritériosdaInternationalDiabetesFederation.Desempenhopreditivo foidescritoapartirdasestimativasdesensibilidade,especificidadeeacuráciaglobal(áreasob acurva)utilizando-sedométododecurvasReceiverOperatingCharacteristic.
Resultados: Ostrêscritériosdiagnósticoapresentarammaioresvaloresabsolutosde sensibili-dadeeespecificidadeparapredic¸ãodaSMetnosrapazesenosadolescentescommaisidade. MaiorsensibilidadeparaidentificarSMetfoiobservadautilizandoocritérioIOTF(60%a85%), enquantoespecificidade≥90%foiobservadamedianteousodostrêscritériosdiagnósticos.O critériodiagnósticoConde&Monteiroapontouacuráciaglobal(0,52a0,64)significativamente menorqueoscritériosdiagnósticosWHO(0,70a0,84)eIOTF(0,75a0,89).
Conclusões: Sobrepesoeobesidade apartir doIMC mostrouuma moderadaassociac¸ãocom
SMet,independentementedocritériodiagnósticoempregado.Contudo,ocritérioIOTF demon-stroumelhor capacidadepreditiva para presenc¸ade SMetque oscritérios WHOeConde & Monteiro.
©2017SociedadeBrasileiradePediatria.PublicadoporElsevierEditoraLtda.Este ´eumartigo OpenAccesssobumalicenc¸aCCBY-NC-ND(http://creativecommons.org/licenses/by-nc-nd/4. 0/).
Introduction
Currently, regardless of gender, age, socioeconomic stratum,andgeographical region,overweight andobesity have become a global epidemic,1 which definitively con-tributestotheonsetofcardiovascularriskbiomarkers.2In recent years, there have been significant changes in the understandingofbiomarkersimplicatedinthepathogenesis of cardiovascular diseases, including the identification of proinflammatory and anti-inflammatory cytokines, adipokines, chemokines, inflammatory indicators derived fromhepatocytes,andsomespecificenzymes.3However,at youngages,theuseoftheso-calledtraditionalrisk biomark-ers still prevails, with emphasis on metabolic syndrome (MetS).4---6
Nonetheless, the complexity of the procedures neces-sarytoidentifyMetSmakesit difficulttoinclude themin routinesfor healthstatus monitoringin youngindividuals, whichrequire alternativesthat aremore practical andof immediateuse.Inthissense,previousstudiespresented evi-dencethat overweightandobesity,identifiedthroughthe bodymass index(BMI), aredefined aspossible predictors ofMetS.7---9Therefore,adequateclassificationofoverweight and obesity may constitute an important complementary screeningtoolforthepresenceofMetSinchildrenand ado-lescents.
Theuseofadiagnosticcriterionofoverweightand obe-sitybasedonBMItoscreenMetSinadolescentsisjustified, asitisanaccessibleandeasy-to-usealternative,whichhas immediateinterpretationandgoodcost-effectiveness. How-ever, it does not seek toreplace medical intervention at any time, sinceit does not exclude the need to monitor
the individual componentsto confirm the MetSdiagnosis. Ascreeningprocess,whenperformedinenvironmentswith high concentrations of young individuals, suchas schools, reachesahighnumberofadolescents,especiallythosewho havedifficultyaccesstoordonotseekthehealthsystem. Therefore,oncethe adolescentsmostlikelytohave MetS have beenidentified,theycanbereferredfor specialized medicalfollow-up.
There is a consensus regarding the diagnostic criteria toclassifyoverweightandobesity inadultsbasedonBMI; however,thisisnotthecasefor childrenandadolescents. Considering the implications related to the processes of physicalgrowthandbiologicalmaturationthatstartatthis stageofdevelopment,thesignificanceofBMIforthehealth ofyoungindividualscallsformorecomplexdifferentiations thanthoseattributedtoadults.Inthiscase,different diag-nosticcriteriabasedonBMIhavebeen proposedandhave been used to identify excess body weight in young indi-viduals.Intheinternationalcontext,thecriteriasetforth by=theWorldHealthOrganization(WHO)10,11andthe Inter-national ObesityTask Force(IOTF)12,13 standout,whereas theproposalofConde andMonteiro14 hasreceivedspecial attentionfor thespecific useintheyoung Brazilian popu-lation.However,thereis noconsensusonthe proposalto be used and, therefore, there are discussions about the validityof each diagnostic criterionwhen usedin specific populations.
Table1 Diagnosticcriteriaforidentifyingexcessbodyweightinyoungindividualsbasedonbodymassindex(BMI)according totheWorldHealthOrganization(WHO),InternationalObesityTaskForce(IOTF)andCondeandMonteiro.
Diagnosticcriteria Referencesurvey Overweight Obesity
WHO YoungNorth-Americans
individuals.Datacollectedin 1971---74
Percentiledistribution consideringBMIbetweenthe 85thand95thpercentiles
Percentiledistribution consideringBMIabovethe 95thpercentile
IOTF Youngindividualsfromsix countries(UnitedStates,Great Britain,Brazil,Singapore,the Netherlands,andHongKong). Datacollectedbetween1973 and1993.
Cutoffobtainedthrough mathematicaladjustment, consideringadultBMIbetween 25and30kg/m2
Cutoffobtainedthrough mathematicaladjustment, consideringadultBMIabove 30kg/m2
Condeand Monteiro
YoungBrazilianindividuals. Datacollectedin1989.
Cutoffobtainedthrough mathematicaladjustment, consideringadultBMIbetween 25and30kg/m2
Cutoffobtainedthrough mathematicaladjustment, consideringadultBMIabove 30kg/m2
Methods
The study is linked to a larger project, which aimed to estimatetheprevalenceof MetSandassociatedfactorsin adolescents. For that purpose, a population-based cross-sectional study was carried outin students fromthe city ofJacarezinho,stateofParaná,Brazil.Datacollectionwas carriedoutfromAugust toNovember2014. The interven-tion protocols used in the study were approved by the Research Ethics Committee of Universidade do Paraná ---UNOPAR(Opinionn.1,302,963).
Sampleandsubjectselection
Thereferencepopulationincludedadolescentsofboth gen-ders, aged 12 to 20 years,enrolled in public and private elementaryschools (6thto9thgrade)andhighschool(1st to3rd year). Initially, the sample size wasestablished to meet the objective of estimating the prevalence of MetS andassociatedfactors,assuminga95%confidenceinterval, asamplingerrorof3percentagepoints,anincreaseof10% forpossiblelossesand,asthesampleplanninginvolved con-glomerates(schoolstructure,gender,schoolshiftandschool year),adesigneffect(deff)equalto1.5wasadded.
According to the procedures used to calculate sample size in studies involving diagnostic tests,15 it wasverified thatthissample,whichincluded1035adolescents,allowed theadequateidentificationofsensitivityandspecificity.The sample’sstatisticalpower,stratifiedbygender(565girlsand 470 boys),wascalculated aposteriori andallowsto con-sider,with80%powerand5%significance,areasunderthe receiveroperatingcharacteristic(ROC)curveofatleast0.53 and0.56forgirlsandboys,respectively.
Datacollection
Chronological age was established in years and months, basedonthecomparisonbetweenthedatacollectiondate andbirthdate.However,fortheanalysisofdata,twoage groupswereestablished:12---15yearsand16---20years.
BMIwascalculatedusingtheratiobetweenbodyweight in kilograms and height expressed in meters squared (kg/m2), based on the procedures of the World Health
Organization.16 Overweight and obesity were identified usingthethreespecific diagnosticcriteriafor gender and age:WHO,11IOTF,13andCondeandMonteiro,14asexplained inTable1.
MetS wasidentified by analyzing the blood content of plasmalipids(triglyceridesandhigh-densitylipoproteins ---HDL-cholesterol)andbloodglucose,restingbloodpressure (systolic and diastolic), and abdominal fat accumulation (waist circumference), according to the criteria pro-posed by the International Diabetes Federation (IDF).17 In this case, MetS was defined as the mandatory pres-ence of elevated waist circumference (<16 years: both genders ≥ 90th percentile; ≥ 16 years: boys ≥ 90cm
and girls ≥ 80cm) and at least two other altered
com-ponents: increased triglycerides (≥150mg/dL), decreased
HDL-cholesterol(<16 years: both genders<40mg/dL; ≥16
years:boys<40mg/dL andgirls<50mg/dL),elevated fas-tingbloodglucose(≥100mg/dL),andalteredbloodpressure
(systolic≥130mmHgordiastolic≥85mmHg).
The measurementsof plasmalipids andglycemia were carriedoutinbloodsamplescollectedbyvenipunctureafter 12hoffasting,accordingtoconventionallaboratory tech-niques. Systolic and diastolic blood pressure levels were measured through the auscultatory method using a mer-curysphygmomanometer,withtheadolescentinthesitting position,aftera minimumof 5min of rest. Two measure-mentswereperformed,consideringthemeanvalueofboth measures for calculation purposes. Waist circumference measurementsweremadeatthemidpointbetweenthelast ribandtheiliaccrest,usinganinextensibleanthropometric tape.
Statisticalanalysis
Table2 Prevalencerates(95%confidenceinterval)ofoverweightandobesityestimatedbythethreediagnosticcriteriaand metabolicsyndromeinthepopulationofadolescentstudentsanalyzedinthestudy.
Girls Boys 2test
12---15years 16---20years 12---15years 16---20years Gender Age
Overweight
WHO 16.5(15.1---18.2) 20.5(18.6---22.7) 17.1(15.6---19.8) 18.8(17.2---20.6) ns p=0.041 IOTF 15.5(14.2---17.0) 18.2(16.7---19.9) 14.2(12.9---15.7) 16.3(14.9---17.9) ns p=0.048 CondeandMonteiro 16.9(15.4---18.6) 22.8(20.7---25.1) 17.9(16.2---19.8) 21.0(19.0---23.2) ns p=0.030
2test ns p=0.020 p=0.032 p=0.002
Obesity
WHO 5.2(4.3---6.3) 6.5(5.6---7.6) 5.9(5.1---6.9) 6.6(5.7---7.7) ns ns IOTF 4.9(4.1---5.9) 5.8(5.0---6.8) 4.7(4.0---5.6) 5.0(4.2---5.9) ns ns CondeandMonteiro 5.3(4.3---6.4) 7.2(6.2---8.3) 6.1(5.1---7.2) 7.3(6.3---8.5) ns ns
2test ns p=0.049 ns p=0.041
Overweight+obesity
WHO 21.7(19.7---23.9) 27.0(24.8---29.4) 23.1(21.1---25.3) 25.5(23.3---27.8) ns p<0.001 IOTF 20.4(18.5---22.4) 24.0(22.0---26.2) 18.9(17.1---20.9) 21.4(19.4---23.6) ns p=0.036 CondeandMonteiro 22.2(20.1---24.5) 30.1(27.7---32.6) 24.0(21.8---26.4) 28.3(26.0---30.9) ns p<0.001
2test ns p<0.001 p<0.001 p<0.001
Metabolicsyndrome 3.3(2.6---4.2) 4.1(3.2---5.2) 4.3(3.4---5.4) 5.9(4.9---7.0) p=0.046 p=0.038
WHO,WorldHealthOrganization;IOTF,InternationalObesityTaskForce.
stratified for gender and age. Statistical differences betweenthestratainvestigatedwereanalyzedwiththe chi-squaredtest(2)forlineartrends.Theperformanceofthe
threediagnosticcriteriaforoverweightandobesity(WHO, IOTF, andConde and Monteiro) aspredictors of MetS was analyzed usingsensitivity, specificity, and global accuracy properties, identified by the ROC curve method together with their 95% confidence intervals.18 Possible significant differencesrelatedtothesensitivity,specificity,and over-allaccuracypropertieswereidentifiedusingMcNemar(2) statistics.19
Results
Table 2 shows the prevalence rates of overweight, obe-sity,andMetSintheadolescentpopulationanalyzedinthe study.Thehighestprevalencerateswereobservedusingthe diagnosticcriterionbyCondeandMonteiro,mainlyin ado-lescentsagedbetween16and20years.Conversely,theIOTF diagnosticcriterionindicatedsignificantlylowerprevalence rates,especiallyinboys.MetSwasidentifiedin4.5%(95%CI: 3.8---5.4)ofthesample,beingsignificantlyhigherinboysand olderadolescents.
Theperformanceofthethreediagnosticcriteriafor over-weightandobesityaspredictorsofMetSisshowninTable3. Overall,bothoverweightandobesityshowedsimilar sensi-tivityinbothgenders;however,highervalueswereobserved inolderadolescents.Asforspecificity,therewasatendency forthevaluesobservedingirlstostandoutwhencompared withthoseobservedinboys,withnoimportantsignificant inrelationtoage.
In both genders,regardless of age andthe three diag-nostic criteria, the sensitivity for obesity was higher, while greater specificity was observed for overweight. In
all assessed strata, the IOTF diagnostic criterion showed the highest sensitivity. In turn, the lowest sensitivity was observed when using the Conde and Monteiro diagnostic criterion. As for specificity, the three diagnostic criteria showedsimilarvalues,closeto90%.
Regardingthe overall accuracy property, which ranged between 0.52 and 0.89, differences between age ranges were more pronounced than between genders. Regarding the diagnostic criteria, the Conde and Monteiro proposal showedasignificantlylowerglobalaccuracythantheWHO andIOTFproposals.The useofthe diagnosticcriterionby CondeandMonteiroshowedvalues≤0.69,whichsuggests
lowoverallaccuracy.Inturn,theuseoftheWHOandIOTF diagnostic criteriashowedvalues between 0.70and 0.89, with a significant advantage for the IOTF criterion, thus showingmoderateglobalaccuracy.
Discussion
Regardlessofthediagnosticcriteriaused,oneinfour adoles-centsanalyzedinthestudyhadexcessbodyweight(≈25%).
This proportion is similar to that found in a representa-tive studyof a groupof medium-sizedand largeBrazilian municipalities20;however,slightlylowerthanthatof devel-oped countries and approximately twice as high as that observedintheyoungpopulationofdevelopingcountries.1 Usingthesamediagnosticcriteria(IDF),theproportionof adolescentswithMetSishigherthanthatrecentlyobserved in the young Brazilian population (4.5% vs. 2.6%)21; how-ever,itislowerthanthatdescribedinNorth-Americanand Europeanadolescents.22
Table3 Performance ofWHO, IOTF, andConde andMonteiro diagnostic criteria ofoverweight and obesity as metabolic syndromepredictors.
Sensitivity(95%CI) Specificity(95%CI) Overallaccuracy(95%CI)
12---15years 16---20years 12---15years 16---20years 12---15years 16---20years
Overweight Girls WHO 53.9 (51.8---56.1) 61.0 (58.7---63.3) 95.1 (92.0---98.3) 92.6 (89.2---95.7) 0.70 (0.66---0.75) 0.76 (0.71---0.81) IOTF 59.4 (57.2---61.7) 67.1 (64.7---69.5) 93.6 (90.6---96.6) 93.1 (90.1---96.1) 0.75 (0.71---0.80) 0.82 (0.77---0.87) CondeandMonteiro 46.2
(44.4---48.1) 50.6 (48.6---52.7) 94.4 (91.2---97.8) 93.9 (90.8---97.0) 0.52 (0.49---0.56) 0.57 (0.54---0.61)
2test p<0.001 p<0.001 ns ns p<0.001 p<0.001
Boys WHO 54.8 (52.8---56.9) 64.1 (61.8---66.5) 90.5 (87.6---93.5) 89.8 (86.9---92.8) 0.71 (0.67---0.75) 0.78 (0.73---0.83) IOTF 60.1 (58.0---62.2) 70.6 (68.2---71.1) 91.0 (88.2---93.9) 88.4 (85.6---91.3) 0.79 (0.75---0.83) 0.86 (0.81---0.91) CondeandMonteiro 47.2
(45.4---49.1) 50.7 (49.6---54.0) 92.8 (89.7---96.1) 90.5 (87.5---93.6) 0.54 (0.51---0.57) 0.59 (0.55---0.61)
2test p<0.001 p<0.001 ns ns p<0.001 p<0.001
Obesity Girls WHO 76.8 (74.0---79.7) 77.3 (74.5---80.1) 90.6 (87.6---93.7) 88.5 (85.7---91.3) 0.73 (0.69---0.77) 0.84 (0.79---0.89) IOTF 84.0 (81.0---87.1) 82.9 (80.0---85.9) 91.8 (88.7---94.9) 89.0 (86.1---91.9) 0.78 (0.78---0.82) 0.88 (0.83---0.93) CondeandMonteiro 51.5
(49.4---53.6) 54.1 (51.7---56.6) 93.1 (90.0---96.2) 90.7 (87.8---93.6) 0.54 (0.51---0.57) 0.64 (0.40---0.68)
2test p<0.001 p<0.001 ns ns p<0.001 p<0.001
Boys WHO 72.2 (69.6---74.8) 78.0 (75.2---80.2) 89.1 (86.3---91.9) 87.7 (84.9---90.5) 0.78 (0.73---0.83) 0.84 (0.78---0.89) IOTF 81.6 (78.8---84.4) 84.2 (81.1---87.4) 89.5 (86.6---92.4) 88.2 (85.4---91.0) 0.85 (0.79---0.90) 0.89 (0.84---0.93) CondeandMonteiro 52.2
(50.0---54.5) 54.4 (51.6---57.3) 91.6 (88.5---94.7) 90.4 (85.5---91.4) 0.56 (0.52---0.60) 0.63 (0.59---0.67)
2test p<0.001 p<0.001 ns ns p<0.001 p<0.001
WHO,WorldHealthOrganization;IOTF,InternationalObesityTaskForce.
showedthatthechancesofcorrectly identifyingthe pres-enceofMetSwhenusingthisdiagnosticcriterionwereclose to 50---60% (area under the ROC curve between 0.52 and 0.64).Inthiscontext,if,ontheonehand,thespecificities obtainedwhenusingtheCondeandMonteirodiagnostic cri-terionshowedvalues≥90%,ontheotherhand,the
sensitivi-tiesdidnotexceed55%.Therefore,whenusingthis diagnos-ticcriteriontoidentifyMetS,thereisahighprobabilitythat adolescentswithnormalweightwillbeidentifiedasnot hav-ingMetS;however,thechanceofdetectingMetSmarkedly decreasesinadolescentswhoareoverweightorobese.
The predictive capacities of the WHO and IOTF diag-nosticcriteriaforthepresence ofMetSwereshowntobe higherandwithlowerdifferencesbetweenthem;however, the IOTF diagnostic criterion showed significantly higher sensitivitythantheWHOandtheCondeandMonteiro crite-ria. In this sense, the use of the IOTF diagnostic criteria
to correctly identify MetS resulted in 5---10% and 13---22% fewer false-negative cases than the WHO and the Conde andMonteirodiagnosticcriteria,respectively.In probabilis-ticvalues,usingtheWHOandIOTFdiagnosticcriteria,out of ten adolescents with excess body weight, there were alsoindications thatapproximatelyseven tonine ofthem werecorrectlyidentifiedashavingMetS(areaundertheROC curvebetween0.70and0.89).
Although significant differences were found related to thesensitivity,specificity,andoverallaccuracyproperties, thefindingsofthepresentstudyconfirmed thatthethree diagnostic criteria are capable of predicting MetS, with more adequate validity indicators in obese adolescents. Inthis context,it is important tomentionthat the three diagnosticcriteriahavetheuseofarbitrarycutoffsin com-mon,based mainly on statistical assumptions. Therefore, thesedifferencesmaybeexplainedinpartbythedifferent methodologiesusedintheirpropositionsand,mainly,bythe prevalenceratesofoverweightandobesityandthesecular tendency ofBMI ofthe referencepopulation usedfor the sampledataset.
The WHO proposalis basedondata fromyoung North-Americanindividuals collected from 1971 to 1974; it was recentlyreprocessedtoattenuatelimitationsdetectedina previousproposal.11 Whiletheremaybeevidencethatthe prevalenceofoverweightandobesityintheyoung popula-tionof theUnitedStatesshowedastabilizing tendencyin thelastdecade,thisis notthecase whencomparingdata fromthe1970sandfrommorerecentgenerations.24
In turn, the IOTF proposal originates from representa-tivenationalsurveysofyoungindividualsfromsixcountries (UnitedStates,GreatBritain,Brazil,Singapore,the Nether-lands, and Hong Kong). The surveys were carried out at differenttimesbetween1973and1993,12,13 whichhinders the analysis of the secular trend of BMI when proposing thisdiagnosticcriterion.TheCondeandMonteiroproposal useddata extracted from the National Health and Nutri-tion Survey, involving a nationally representative sample of young Brazilian individuals.14 Data were collected in 1989,whentheprevalenceofoverweightandobesityinthe young Brazilian population wassignificantly lowerthan in thepresentday.20
Furthermore, when selecting a specific diagnostic cri-terion, it is prudent to consider the influence of ethnic components.Inthissense,foruseinBrazilianadolescents, theCondeandMonteirodiagnosticcriterioninitiallyshowed great advantage and, in contrast, even considering the multiethnic profile of the young American population, an importantlimitationshouldbeaccountedforwhenchoosing theWHOdiagnosticcriteria. TheIOTFdiagnosticcriterion appearstobemoreadequatetoensureamultiethnic appli-cation,asitis basedondatafromsixcountries,including Brazil.
Regarding thedifferentmethodologiesusedtoidentify cutoffs,the WHO proposal usedprobabilistic resources in whichBMIvaluesequivalenttothe85thand95thpercentiles were usedto identify overweight and obese adolescents, respectively.Therefore,itwasassumedthat,inthe refer-encepopulation, regardlessofanyadditionalinformation, exactly15%oftheyoungindividualsofeachgenderandage wereoverweightand5%wereobese.Animportant limita-tionofthismethodologyisthatitconsidersthathigherBMI valuesinthepercentiledistributionofthereference popula-tionmayrepresentthepresenceofoverweightandobesity, ratherthan justidentifyingindividualswhoareheavierin comparisontotheirpeers.
Incontrast,the IOTFandtheConde andMonteiro pro-posalswerecreatedindependentlyfromtheBMIpercentile distributioninthereferencepopulation.Inthesecases,the cutoffsweredefinedusingepidemiological criteria,based
on adjustments of specific mathematical models for gen-der and age, in which at age of 18 years there was an interception with BMI values representative of increased risk for the presence of health outcomes in early adult-hood, as a consequence of overweight and obesity, i.e., 25kg/m2and30kg/m2,respectively.However,the method-ological procedure usedby the two proposalsis not free of criticism. Although they do not depend on the per-centiledistribution,itwasassumed thattheproportionof young individuals in the reference population with over-weightandobesitywasthesameinbothgendersandatall ages.
Thepresentstudyresultscorroboratefindingsavailable intheliteraturethatindicatehighspecificityaccompanied by reasonable sensitivity to identify cardiometabolic risk in youngindividuals usingdiagnosticcriteriabasedonthe BMI.7---9However,itpartiallydisagreeswiththeresultsfound ina studyofBrazilianchildren thatsoughttoidentifythe predictivecapacityofdiagnosticcriteria,specificallyforthe presenceof highblood pressure.25 Thestudyshowed indi-catorsequivalenttooverall accuracy thatweresimilarto the diagnosticcriteria byConde and Monteiro andby the IOTF. Possibly,the isolateduseof thehigh blood pressure component, ratherthan the conglomerateof components that definesMetS, andthe youngerage of the study sub-jects(childrenbetween6and13yearsofage)canexplain possibledivergencesbetweenbothstudies.
The present study has some limitations thatshould be considered.Evenassumingthelowrateofrefusaltoundergo the measurements(≈8%), the possibilityof selection bias
cannotberuled out,sinceitwasnotpossibletocompare datafromtheadolescentsthatparticipatedandthosewho didnotparticipateinthestudy.Itisalsoimportantto men-tionthat,becausethereisnouniversalcriteriontodefine MetS, the authors chose to use criteria proposed by the IDFand,inthissense,MetSprevalenceestimatesmayvary accordingtotheusedcriteria.26,27
In conclusion, evidence found in the study contribute tothe knowledge ofthe area,showingthat, of thethree diagnosticcriteriaofoverweightandobesitybasedonBMI (WHO, IOTF, and Conde and Monteiro), the IOTF diag-nostic criterion showed a significantly higher predictive capacity for the presence of MetS.However, since BMI is an important predictor of the presence of MetS in ado-lescents, the major challenge remains to adjust cutoffs that can minimize the number of false-negative results (higher sensitivity indices) and maximize the amount of true-negative cases (higher specificity indices), as previ-ouslyobservedinthethreediagnosticcriteriaconsideredin thestudy.
Funding
DartagnanPintoGuedesisaResearchProductivityFellowat CNPq.
Conflicts
of
interest
References
1.NgM,FlemingT, RobinsonM,ThomsonB,GraetzN,Margono C,et al. Global, regional,and nationalprevalence of over-weightand obesityinchildrenand adultsduring1980---2013: asystematicanalysisfor theGlobalBurdenofDiseaseStudy 2013.Lancet.2014;384:766---81.
2.AhimaRS,LazarMA.Thehealthriskofobesity---bettermetrics imperative.Science.2013;341:856---8.
3.US Preventive Services TaskForce. Usingnontraditional risk factorsincoronaryheartdiseaseriskassessment:U.S. Preven-tiveServicesTaskForcerecommendationstatement.AnnIntern Med.2009;151:474---82.
4.ZimmetP,AlbertiG,KaufmanF,TajimaN,SilinkM,Arslanian S,etal.Themetabolicsyndromeinchildrenandadolescents. Lancet.2007;369:2059---61.
5.GrundySM.Metabolicsyndromepandemic.ArteriosclerThromb VascBiol.2008;28:629---36.
6.PapakonstantinouE,LambadiariV,DimitriadisG,ZampelasA. Metabolicsyndromeandcardiometabolicriskfactors.CurrVasc Pharmacol.2013;11:858---79.
7.Freedman DS, Fulton JE, Dietz WH, Pan L, Nihiser AJ, SrinivasanSR,etal.Theidentificationofchildrenwithadverse riskfactor levelsbybodymassindex cutoffsfrom two clas-sificationsystems:theBogalusaHeartStudy. AmJClinNutr. 2010;92:1298---305.
8.KakinamiL, Henderson M, Delvin EE, Levy E, O’Loughlin J, LambertM,etal.Associationbetweendifferentgrowthcurve definitionsofoverweightandobesityandcardiometabolicrisk inchildren.CMAJ.2012;184:E539---50.
9.LaursonKR,WelkGJ, EisenmannJC.Diagnosticperformance ofBMIpercentilestoidentifyadolescentswithmetabolic syn-drome.Pediatrics.2014;133:e330---8.
10.World Health Organization. Child Growth Standards based on length/height, weight and age. Acta Paediatr Suppl. 2006;450:76---85.
11.deOnisM,OnyangoAW,BorghiE,SiyamA,NishidaC,Siekmann J.DevelopmentofaWHOgrowthreferenceforschool-aged chil-drenandadolescents.BullWorldHealthOrgan.2007;85:660---7. 12.Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standarddefinitionforchildoverweightandobesityworldwide: internationalsurvey.BMJ.2000;320:1240---3.
13.ColeTJ,LobsteinT.Extendedinternational(IOTF)bodymass index cut-offs for thinness, overweight and obesity. Pediatr Obes.2012;7:284---94.
14.CondeWL,MonteiroCA.Bodymassindexcutoffpointsfor evalu-ationofnutritionalstatusinBrazilianchildrenandadolescents. JPediatr(RioJ).2006;82:266---72.
15.LwangaSK,LemeshowS.Samplesizedeterminationinhealth studies:a practicalmanual. Geneva:WorldHealth Organiza-tion;1999.
16.World Health Organization. Physical status: the use and interpretationofanthropometry.ReportofaWHOExpert Com-mittee.854.Geneva:WHO;1995.WHOTechnicalReportSeries. 17.AlbertiKG,ZimmetP,ShawJ.Metabolicsyndrome:anew world-widedefinition.Aconsensusstatementfromtheinternational diabetesfederation.DiabetMed.2006;23:469---80.
18.AkobengAK.Understandingdiagnostictest:receiveroperating characteristiccurves.ActaPaediatr.2007;96:644---7.
19.TrajmanA,LuizRR.McNemar2testrevisited:comparing sen-sitivityandspecificityofdiagnosticexaminations.ScandJClin LabInvest.2008;68:77---80.
20.BlochKV,KleinCH,SzkloM,KuschnirMC,AbreuGA,Barufaldi LA,etal.ERICA:prevalênciasdehipertensãoarteriale obesi-dadeemadolescentesbrasileiros.RevSaudePublica.2016;50 Suppl.1:9s.
21.KyscguburNC,BlochKV,SzkloM,KleinCH,BarufaldiLA,Abreu GA,etal.ERICA:prevalênciadesíndromemetabólicaem ado-lescentesbrasileiros.RevSaudePublica.2016;50Suppl.1:11s. 22.TailorAM,PeetersPH,NoratT,VineisP,RomaqueraD.Anupdate ontheprevalenceofthemetabolicsyndromeinchildrenand adolescents.IntJPediatrObes.2010;5:202---13.
23.DanielsSR,KhouryPR,Morrison JA.Theutilityofbodymass indexasameasureofbodyfatnessinchildrenandadolescents: differencesbyraceandgender.Pediatrics.1997;99:804---7. 24.OgdenCL,CarrollMD,KitBK,FlegalKM.Prevalenceof
child-hoodandadultobesityintheUnitedStates,2011---2012.JAMA. 2014;311:806---14.
25.MoraesLI,NicolaTC,JesusJS,AlvesER,GiovaninniNP,Marcato DG,etal.Highbloodpressureinchildrenanditscorrelation withthreedefinitionsofobesityinchildhood.ArqBrasCardiol. 2014;102:175---80.
26.Cavali ML, Escrivão MA, Brasileiro RS, Taddei JA. Metabolic syndrome:comparisonofdiagnosiscriteria.JPediatr(RioJ). 2010;86:325---30.
