LETTERSTOTHEEDITOR 321
Reply:
Vertical
segmental
tetrapolar
bioimpedance
for
excess
body
fat
assessment
in
adolescents
夽,夽夽Resposta:
Bioimpedanciometria
tetrapolar
segmentada
vertical
para
a
avaliac
¸ão
do
excesso
de
gordura
corporal
em
adolescentes
DearEditor,
ThequestionspresentedbyProfessorDr.RobertoFernandes daCostaandDr.EdilsonSerpeloniCyrinoarerelevantand, therefore,wewouldliketoclarifythecommentssubmitted totheJournal.
First, we value scientific discussion, and the questions raised by the esteemed researchers contributed to the understandingofourfindings.
As for the question concerning the use of the Biodynamics®device(model450,WA,USA)asourreference technique,we emphasize thattheliteratureconfirms this methodologicalchoice.
Asanexample,Goncalvesetal.1foundthatsuch
equip-ment had a good predictive capacity in detecting excess bodyfatinadolescents.Inaddition,theystatedthateven withtheimpossibilityofcompliancewiththemeasurement protocol,theresultsalsoweresimilartothoseofthe dual-energyX-rayabsorptiometry(DEXA).
Nevertheless, weemphasize thatwedidnotstate that thedevicewasusedinourresearchasthegoldstandard,as werecognizethatithaslimitationsandshouldnotbe con-sideredahomologousreplacementfortheindirectmethods: DEXA,hydrostaticweighing,plethysmography,etc.
Also,wedidnotstatethatwewerevalidatingtheTanita® (BC-558model;Amsterdam,Netherlands)vertical segmen-tal tetrapolar bioimpedance device. We proposed,on the contrary,tobrieflycompareitwithanotherdevice,whose useissupportedfor adultandpediatricpopulation assess-ment,in additiontothefactthat itis moreaccessiblein clinicalpractice.2
We also take this opportunity to point out a correc-tion:thefat-freemassoftheparticipantssubmittedtothe examinationswas estimated usingthe equations reported byChumleaetal.intheirstudy:‘‘Specificresistivityused toestimate fat-free mass from segmentalbody measures ofbioelectricimpedance’’.3However,wemade amistake
in the reference section and cited another publication: ‘‘Predictionof bodyweightfor thenonambulatory elderly fromanthropometry’’.4
DOIofreferstoarticle:
http://dx.doi.org/10.1016/j.jped.2016.03.001
夽 Please cite thisarticle as:Neves FS, Netto MP, Oliveira RM,
Cândido AP. Reply: Vertical segmental tetrapolar bioimpedance
for excessbodyfatassessmentinadolescents. JPediatr (RioJ).
2016;92:321---2.
夽夽StudycarriedoutatDepartmentofNutrition,Institutode
Ciên-ciasBiológicas,UniversidadeFederaldeJuizdeFora(UFJF),Juiz
deFora,MG,Brazil.
Regarding the statistical analysis, we used a strin-gent sampling procedure and data that met specific requirements, namely: (a) the dependent variables were quantitativeandcontinuous,andweremeasuredinatleast oneintervalscale;(b)therewashomoscedasticitybasedon Levene’stest(homogeneityofvariance);(c)thesamplesize waslargeandcamefromapopulationwithnormal distribu-tion.Webelieve,therefore,thattherewasagreementwith thecentrallimittheorem.
It is noteworthy that especially for large samples, the parametric tests (Student’s t-test and ANOVA) are more sensitiveandhave amorerobust behaviorevenwhenthe distributionofthestudyvariableshowsheteroscedasticity andisdemonstrablynotthenormaltype.5
Therefore, the use of non-parametric tests, when the assumptionsarenot valid,eventhough traditional,is not theonlystrategyofanalysis.5
Additionally, aiming to clarify the uncertainties that couldstillpersistfortheprofessors,authorsoftheletter,or otherreaders,weappliedtheKolmogorov---Smirnovtestand thenrepeatedthebivariateanalyses,submittingthe varia-blesconsideredasnon-parametrictotheMann---WhitneyU
test. As a result, the interpretations of the significances remainedequivalenttothoserecordedinthestudy.
Nevertheless,thefocusofourinvestigationwasdirected atthereceiveroperatingcharacteristic(ROC)curves,and the parametric or non-parametric considerations did not impairouraims.
Regardingthepositiveandnegativepredictivevalues,we agreewiththecommentthatapost-testprobabilityanalysis wouldsubstantiallycomplementtheresultsfound.
Considering our justifications, we hope that this dis-cussion will contribute to clarify the efficacy of vertical segmentaltetrapolarbioimpedance,andencouragefurther studiesthatwilladdressthesamesubject.
Inconclusion,wekindlythanktheprofessorswhowere willingtoevaluateourwork.
Funding
Conselho Nacional de Desenvolvimento Científico e Tec-nológico.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
References
1.Gonc¸alvesVS,FariaER,FranceschiniSdoC,PrioreSE.Predictive capacityofdifferentbioelectricalimpedance analysisdevices, withandwithoutprotocol,inevaluationofadolescents.JPediatr (RioJ).2013;89:567---74.
2.Associac¸ão Brasileira de Nutrologia, Sociedade Brasileira de Nutric¸ão Parenteral e Enteral. Utilizac¸ão da bioimpedância para avaliac¸ão da massa corpórea. Projeto diretrizes; 2009. Availablefrom:http://www.projetodiretrizes.org.br/8volume/ 39-Utilizacao.pdf[cited01.02.16].
322 LETTERSTOTHEEDITOR
4.ChumleaWC,GuoS,RocheAF,SteinbaughML.Predictionofbody weightforthenonambulatoryelderlyfromanthropometry.JAm DietAssoc.1988;88:564---8.
5.Marôco J.Análise estatísticacom o SPSSStatistics. In:Testes paramétricosparaamostrasindependents.6thed.PerôPinheiro: ReportNumber;2014.p.183---9.
FelipeS.Nevesa,MichelePereiraNettob,
RenataMariaSouzaOliveiraa,AnaPaulaCarlosCândidoc,∗
aUniversidadeFederaldeJuizdeFora(UFJF),Juizde
Fora,MG,Brazil
bUniversidadeFederaldeMinasGerais(UFMG),
BeloHorizonte,MG,Brazil
cUniversidadeFederaldeOuroPreto(UFOP),OuroPreto,
MG,Brazil
∗Correspondingauthor.
E-mail:anapaula.candido@ufjf.edu.br(A.P.C.Cândido).
