Rev. Bras. Hematol. Hemoter. vol.39 número3

rev bras hematol hemoter. 2017;39(3):189–190

w w w . r b h h . o r g

Revista

Brasileira

de

Hematologia

e

Hemoterapia

Brazilian

Journal

of

Hematology

and

Hemotherapy

Scientific

Comment

Adjusting

thresholds

of

serum

ferritin

for

iron

deficiency:

a

moving

target

夽

Flávio

Augusto

Naoum

AcademiadeCiênciaeTecnologia(AC&T),SãoJosédoRioPreto,SP,Brazil

Irondeficiencyanemia(IDA)iswidelyprevalentinpatientsof allages.1_{Inchildrenandyoungadults,thediagnosisofIDAis}

ratherstraightforward.Inelderlypatients,however,the pres-enceofcomorbiditiesusuallyhamperspromptdiagnosisby conventionalironprofiletests.2

Whenlimitedtoconventionalironmeasuresduring eval-uationsofsuspectedIDAinanelderlypatientwithanormal ferritinlevel,transferringsaturationbecomesmorereliablefor diagnosticpurposes.Comorbidity-related inflammationcan compromisetheaccuracyofirontests,notablyserumferritin, whichisanacutephasereactantitself.2,3_{Therefore,inorderto}

ascertainthediagnosisofIDAinelderlypatients,itisadvisable totakeotherironparametersintoaccount,suchastransferrin saturation.

Moreover,itisimportanttoquestionwhata‘normal’serum ferritinlevelreallyisforthispatient,sinceadoptionof com-monlyusedcut-off values(rangingfrom 15to30ng/mL) to confirmIDAwouldresultinalargenumberofundiagnosed patientsamongtheelderly.4_{Adistinctionbetweenabsolute}

and functional irondeficiency inthis context iscrucial.In absoluteirondeficiency,serumferritinlevelstendtomirror lowironreservesunlessfalselyelevateddueto inflammation-relatedconditions.Ontheotherhand,achronicinflammatory process is frequently associated with functional iron defi-ciency, a condition in which, in spite of satisfactory iron reserveswithnormalorevenincreasedserum ferritin,the availabilityofironforthebonemarrowislimitedsubstantially duetoincreasedhepcidintranscription.5

DOIoforiginalarticle:http://dx.doi.org/10.1016/j.bjhh.2017.02.002.

夽

SeepaperbyBabaeietal.onpages223–8.

∗ _{Correspondingauthorat:AcademiadeCiênciaeTecnologia(AC&T),R.BonfáNatale,1860,SantosDumont,15020-130SãoJosédoRio}

Preto,SPBrazil.

E-mailaddress:drflavio@institutonaoum.com.br

ThestudybyBabaeietal.6_{inthisissueoftheBrazilian}

Jour-nalofHematologyandHemotherapyaimedatobtainingan appropriatecut-offlevelforserumferritinthatwouldbetter discriminatebetweenelderlypatientswithandwithoutIDA. Theauthorshadtheopportunity–andtheprivilege–torecruit averyhomogeneouscohortofelderlypatientsintermsof eth-nicity,demographicsandlifestyle.Athresholdof100ng/mL forserumferritinyieldedasensitivityof60%andspecificityof 59%forIDAdetection,employingalowtransferrinsaturation levelasthereferencetesttoconfirmdiagnosis.

Inthiscontext,asensitivityandspecificityofaround60%to confirmIDAbyadistinctserumferritinthresholdseems rea-sonable,asshownbyBabaeietal.andothers.7_Forinstance,

the cut-off value forhemoglobinA1C todiagnose diabetes mellitus hasalsobeen amatter ofdebate, sincethe tradi-tionally adopted cut-off point of 6.5% onlyaccounts for a sensitivityof43%,whereasatacut-offpointof6.2%,the sen-sitivitywouldincreaseto60%,inspiteofsimilarspecificities forbothpoints.8

Itisnoteworthy,however,thatfindingadistinctive thresh-oldforserumferritininspecificpopulationsisachallenging task thatrelies essentiallyon the choice ofthe parameter adopted as the gold standard for IDA diagnosis. Although transferrin saturation levels have been adoptedfor this in somestudies,their usehaslimitations.Forexample,when stainable ironinthebonemarrowwas adoptedasthe ref-erencestandard,transferrinsaturationlevelsbelow20%had asensitivityof60% andspecificity of48% indetectingIDA

http://dx.doi.org/10.1016/j.bjhh.2017.03.002

190

inanemic patientswith meanage of68;hence,therewas aconsiderableoverlapbetweentheiron-deficientand iron-sufficientgroups.9 _{Alternatively, instead ofselectingagold}

standardmethodtoinfertheapplicabilityofagiventestto confirmIDA,aninterestingandlessinvasiveapproachwould bethecombinationoftheconventionalironmeasureswith newerreliableparameterssuchastransferrinreceptor, retic-ulocytehemoglobinandmeasurementsoftheproportionof hypochromicredbloodcellswhichallowearlyrecognitionof IDA.10

Any effort to improve IDA detection in patients with comorbidities is highly welcome, since misdiagnosing or underdiagnosing this type ofanemia byconventional iron testswithfixedreferencerangescanleadtoinsufficientor equivocaltreatment.Itisimportanttokeepinmindthatiron testsarehighlyvolatileinelderlypatientswithcomorbidities, andpersonalizationofreferencerangesinthisspecific pop-ulationcanimproveaccuracyofIDAconfirmation,especially whenthisconditionisclinicallysuspected.

Conflicts

of

interest

Theauthordeclaresnoconflictsofinterest.

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9789241596657eng.pdf[cited06.03.17].

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Organization/CentersforDiseaseControlandPrevention

TechnicalConsultationontheAssessmentofIronStatusat

thePopulationLevel.Assessingtheironstatusofpopulations

–secondedition,includingliteraturereviews.2nded.Geneva:

Switzerland;2004.

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