WPC N,0 C.| \[~I$+{Bgwo_k5@$Se JP('*>jZrqeȀ!;C6I}-*g7{]:.Y~ގѵɹ꟤cu@h޹X ieR6y: CSf8vù)q8(#U6 % &nNc 0LeUN 0h E UB ` 0h_ UB w 4 ! m# U::  t 0e:&#^  U@ B<\  `(Roman 10cpiX'  XIII. AIHALecture  0 .   #|x<\  `(Roman 10cpiXx\  @ X@($. $      (9 Z 6Times New Roman Regular   z)     _9A" ) xdE9W!A X `3XXX ˭X`3Z ˭XIII.InvestigationofaPositiveDirectAntiglobulinTesttt>T$MLAB2431  141  # ˭Z#(@3z$ . !       ,hAZ*Helvetica Regular  z*     _9A" ) xdEW!A X `3XXX X`3Z MLAB2431  141  0 0 $ $0< $ $0<$<$0$$XIII.InvestigationofaPositiveDirectAntiglobulinTest# Z#(@3z$ . !       +FSAZ*Helvetica Regulara1U{AZ"Arial RegularA, B,Level 1Level 2Level 3Level 4Level 54#,f2Quick A.  .0  potentiatorshp LaserJet 1300 PCL 5e,,,,0uH2 H(C Z(Times New Roman  d . !       _XXHH X`3XXX HXX   XXXX`3XIII.InvestigationofaPositiveDirectAntiglobulinTestandImmuneHemolysis#X`3XXX#  X 9H&]%XX`3&]%%&]A.0  SignificanceofaPositiveDirectAntiglobulinTest(DAT)0$$ 0X,X XHX00  1.0$$Introduction$$ BX,X, XX,X XB0    a.0$$ApositiveDAT doesnot meanthatanindividuals_RBCs_Ԁhaveashortenedsurvival.8$$ 0    b.0$$Asmanyas10%ofhospitalpatients,andbetween1in1000to1in9000blooddonors,willhavea D  positiveDATwithoutclinicalmanifestationsofimmunemediatedhemolysis.  $$ EX ,X XX,X, XE0  2.0$$ApositiveDAT,withorwithoutanassociatedshortenedRBCsurvival,maybecausedbythefollowing  t  phenomenainvivo: L $$ 0    a.0$$ _Autoantibodies_ tointrinsicRBCantigensthatcoat_RBCs_Ԁwithimmunoglobulinorcomplementor T  both.0 $$ 0  0$$b.0$$ _Alloantibodies_Ԁ presentintherecipientofarecenttransfusionthatreactwithantigensondonor_RBCs_.$$ 0  0$$c. 0$$Antibodiespresentindonorplasma,plasmaproductsorbloodfractions thatreactwithantigens < onatransfusion recipient's cells.p$$ 0  0$$d. 0$$Maternal_alloantibodies_ thatcrosstheplacentaandcoatfetal_RBCs_.Theseantibodiesareoften $ associatedwithHDN.$$ 0  0$$e. 0$$Antibodiesdirectedagainstcertaindrugs, suchaspenicillin,thatbindtoRBCmembranes.X$$ 0  0$$f. 0$$Redcellmembranemodifications resultingfromtherapywithcertaindrugs,notablethoseofthe d  cephalosporingroup,leadingtononspecificadsorptionofproteins,includingimmunoglobulins,by @ _RBCs_.$$ 0  0$$g. 0$$Drug/antidrugcomplexes, formedinresponsetotheadministrationofdrugssuchasquinidineand p phenacetin,thatcausecomplementcomponentsandsometimesalsoIgGtobeboundto_RBCs_.L $$ 0  0$$h. 0$$_Heterophile_Ԁantibodies presentinequineantihumanlymphocyteglobulinthatisusedtoreduceT T" cellpopulationsinorganandbonemarrowtransplantrecipients.0 #$$ 0  0$$_i_. 0$$Nonantibodymediatedbindingofimmunoglobulinsto_RBCs_Ԁinpatientswith !% _hypergammaglobulinemia_. ApositiveDATduetothisphenomenonisalsoseeninpatientstreated "d & withhighdoseIV_gammaglobulin_.#@!'$$   3.0  ThePretransfusionDATor_Autocontrol_H%")$$  0    a.0$$ManyworkersusedtoroutinelyperformaDAT(someworkersstilldo),inparallelwithRBCtyping &$+ oran_autocontrol_Ԁinparallelwithserumtestsforunexpectedantibodiesaspartofpretransfusion 'x%, testing.(P&-$$ 0    b.0$$Suchan_autocontrol_ԀservesessentiallythesamepurposeasaDAT;todetermineif_RBCs_Ԁarecoated X*(/ withglobulins.0+(0$$ 0    c.0$$Forthemostpart,theDATdetectsinvivoglobulincoating,whereasthe_autocontrol_Ԁmaybepositive ,*2 duetoinvivo or invitroglobulincoating.-`+3$$  .:,4 0    d.0$$TheneedtoperformaDATor_autocontrol_Ԁaspartofroutine_pretransfusion_Ԁtestinghasbeenthe X subjectofconsiderabledebate,particularlywiththecostrestraintscurrentlyimposedonthehealth 0 careindustry.$$ 0    e.0$$_AABB_ԀStandardsdoesnotrequirethataDATor_autocontrol_Ԁ(AC)beperformedaspartof routine  ` _pretransfusion_Ԁtesting.<$$ 0    f.0$$ReasonsfortheperformanceoftheDATorACareasfollows:D$$ K"X ,X  hXX ,X XK0  0$$0$$1)0 $$toscreenforclinicallyunexpectedautoimmunephenomena and   $ $ 0  0$$0$$2)0 $$todetecttheearlymanifestationofanimmuneresponsetopreviousrecenttransfusions,    particularlyinstancesinwhichthenewlyformed_alloantibody_Ԁhasbeentotallyadsorbedbythe  v  transfused_RBCs_Ԁandcannotbedetectedintheserum. N  $ $ 0  0$$g.0$$IndependentstudieshaveshownthatthereisminimalriskassociatedwitheliminatingtheDAT/AC V  portionofroutine_pretransfusion_Ԁtesting.. $$ 0  4.0$$UnwantedPositive_DATs_ $$ 0    a.0$$TheresultsofDATshouldreflect invivo conditions,andshouldnotbeinfluencedbyinvitro 6 phenomenaassociatedwiththecollection,storageorhandlingofbloodsamples.j$$ 0  0$$b.0$$BeforefurtherstudiesareundertakenonapatientwithapositiveDAT,causesof invitro coating  shouldbeexcluded.$$ 0  0$$c.0$$FalsepositiveDATresultsaremostoftenassociatedwiththeuseofrefrigerated,clottedblood N samplesinwhichcomplementcomponentscoat_RBCs_Ԁinvitro.~&$$ 0  0$$d.0$$AnypositiveDATresultobtainedfromaclottedbloodsampleshouldbeconfirmedusingfreshly . collected,_EDTA_Ԅ_anticoagulated_Ԁspecimen.$$ B.0  EvaluationofaPositiveDAT^$$   1.0  Extentoftesting.f $$ 0    a.0$$ ClinicalconsiderationsshoulddictatetheextenttowhichapositiveDATisevaluated. "$$ 0    b.0$$Dialoguewiththeattendingphysicianisimportantbeforeanyadditionalserologicaltestsare  r$ undertaken.!J%$$ 0    c.0$$Interpretingthesignificanceofserologicalfindingsrequiresknowledgeof thepatient'sdiagnosis, R# ' drugtherapyandrecenttransfusionhistory. .$!($$ 0    d.0$$Theresultsofserologicaltest arenotdiagnostic ;theirsignificancecan only beassessedin %#* relationshiptothe patient'sclinicalcondition,andlaboratorydatasuchas_hematocrit_,bilirubin, &b$+ _haptoglobin_Ԁand_reticulocyte_Ԁcount. '>%,$$ 0    e.0$$IfananemicpatientwithapositiveDATmanifestclinicalsignsandsymptomsofhemolysisitis F)&. appropriatetodetermineifthehemolysishasanimmunebasis.Ontheotherhand, ifthereisno *'/ evidenceofhemolysis,nofurtherstudiesarenecessary ,unlessunexpectedantibodiesarepresent *(0 andtransfusionisnecessary.+~)1$$   -.+3 0    f.0$$Approximately3%ofpatientsreceivingIVpenicillinand1520%ofpatientsreceivingalpha X  _methyldopa_Ԁ(_Aldomet_)willdevelopapositiveDAT,butlessthan1%ofthosepatientswillhave 0 hemolyticanemia.theattendingphysicianshouldbealertedsothatappropriatesurveillancefor  hemolysiscanbemaintained,butifthereisnoevidenceofhemolysis,noadditional bloodbank testing  needbedone.b$$ 0    g.0$$TransfusionofnonABOgroupspecificplasmatoAand/orBantigenspresentontherecipient'scells j maygiverisetoapositiveDATandoccasionallymayresultinaccelerateddestructionofthose_RBCs_. B IfsignsofhemolysisoccurinvestigationoftheDATcanbelimitedtodemonstratingthepresenceof   antiAand/orBontherecipient's_RBCs_.  $$ 0    h.0$$Patientsreceivingantilymphocyteglobulin(_ALG_)oranti_thymocyte_Ԁglobulin(_ATG_)producedin  J  horsesdevelopapositiveDATwithinafewdaysaftersuchtherapyisinitiated.Thisappearstobe z "  relatedtohightiter_heterophile_Ԁantibodiesintheseproducts.Theproblemcanbeavoidedusing_AHG_ R  whichhasbeenpartiallyneutralizedwithhorseserum.* $$   2.0  CollectionofBloodSamples $$ 0    a.0$$ToverifythatapositiveDATisnottheresultof invitrouptakeofcomplementcomponentsby 2 clottedspecimens,an_EDTA_Ԅ_anticoagulated_sampleshouldbeobtained. f$$ 0  0$$b.0$$ThisisusedfortheDATandalsoprovidesasourceof_RBCs_Ԁforelutionifnecessary.$$ 0  0$$c.0$$Afreshlycollectedclottedbloodsampleisneededforserumstudies.n$$ 0  0$$d.0$$Ifacold_hemagglutinin_Ԁissuspected,theclottedspecimen shouldbemaintainedat37Cuntilthe v serumhasbeenseparated.R$$  0  3.0$$InitialSerologicalStudies$$ 0  0$$a.0$$TestswithantiIgGandantiC3d_AHG_Ԁreagentstodeterminethetypesofproteinscoatingthe_RBCs_.Z$$ 0  0$$b.0$$Serumteststodetectandidentifyunexpectedantibodies.SuchstudiesshouldbeundertakenatRT, b   37Cand_IAT_Ԁ(antibodyscreenandpanelifnecessary).:!$$ 0  0$$c.0$$Testwithaneluatepreparedfromthecoated_RBCs_Ԁtocharacterizethecoatingantibody.Theeluate # shouldbetestedby_IAT_Ԁagainstpanelcells.ThepanelcellsshouldincludeR1,R2,r_RBCs_Ԁand  j$ includeoneK+,one_Jk_(a+b=)andone_Jk_(a=b+)sample.Ifwarmreactiveautoantibodiesare !B% suspected,thedesignatedRhphenotypesaffordmaximalsensitivityfordetectingautoantibodieswith r" & Rhrelatedactivity(_eg_,autoantie).Ifthepatienthasbeerecentlytransfused,thesuggested J# ' phenotypesservetoprovideoptimalsensitivityfordetecting_alloantibodies_ԀtoRh,_Kell_Ԁand_Kidd_ "$!( systemantigens.Suchantibodiesarefrequentlyassociatedwithanimmuneresponsetorecently $") transfused_RBCs_.%z#*$$ 0  4.0$$FurtherStudies.'*%,$$ 0    a.0$$ WHENNOUNEXPECTEDANTIBODIESAREPRESENTINTHESERUM,ONLY 2)&. _AUTOANTIBODY_ԀISPRESENTINTHEELUATEANDTHEPATIENTHASNOTBEEN *'/ RECENTLYTRANSFUSED,NOFURTHERSEROLOGICALTESTINGISNECESSARY. *(0$$ 0    b.0$$If_alloantibody_Ԁappearstobepresentinserumoreluate,orboth,additionalstudiesmyberequiredto ,>*2 confirmspecificity.n-+3$$  F.+4 0    c.0$$Ifbothserumandeluateare_nonreactive_Ԁatalltestphases,andifthepatientisknowntohavereceived X highdoseIVpenicillin,thentestswithpenicillincoated_RBCs_Ԁshouldbeconsidered.0$$ 0    d.0$$IfthepatienthasbeentransfusedwithABOincompatiblebloodcomponents,suchasgroupOplatelets  administeredtoagroupArecipient,testswithAandB_RBCs_Ԁmaybedonetoascertainwhether ` passivelyacquiredantiAorantiBisresponsibleforthepositiveDAT.8$$ 0    e.0$$Alloimmunehemolysis,resultingin_HDN_Ԁorassociatedwithanimmuneresponsetorecently @ transfused_RBCs_Ԁhasbeendiscussedalready. $$ C.0  ImmuneHemolysis p $$   1.0  Immunehemolysisisdefinedas shortenedRBCsurvivalresultingfromanimmunereaction. x $$   2.0  Ifbonemarrowcompensationisadequate,hemolysismaynotresultinanemia., $$   3.0  Hemolysisisonlyonecauseofanemia,andtherearemanycausesofhemolysisunrelatedtoimmune   reactions.Theserologicalinvestigationscarriedoutinthebloodbank donot determinewhetherapatient \ hashemolyticanemia.8$$   4.0  The diagnosis ofhemolyticanemiarestson clinicalfindingsandlaboratorydatasuchashemoglobin @ or_hematocrit_Ԁvalues,_reticulocyte_Ԁcount,RBCmorphology,bilirubin,_haptoglobin_Ԁand_LDH_Ԁlevels.   Sometimes,RBCsurvivalstudiesareinformative.$$   5.0  Theserologicalfindingshelpdeterminewhetherthehemolysishasanimmunebasisand,ifso,whattype P ofimmunehemolyticanemiaispresent.Thisisimportant,sincethe treatmentforeachtypeisdifferent. ($$   6.0  Immunehemolyticanemiamaybeclassifiedinvariousways.4$$ 0  7.0$$Inoneseriesinvolving300patientswithimmunehemolytic_anemias_, 4870%hadimmunehemolysis  associatedwithwarmreactiveantibodies,16%hadcoldagglutininsyndrome,78%hadmixedtype h _AIHA_,2%hadparoxysmalcold_hemoglobinuria_Ԁand1218%haddruginducedhemolysis. @$$ D.0  WarmAutoimmuneHemolyticAnemia(_WAIHA_)L!$$   1.0  Themostcommontypeofautoimmunehemolyticanemiaisassociatedwithwarmreactive(37C) # antibodies. _WAIHA_Ԁpatientspresent themostdifficultserologicalproblemsyouwillencounterinthe  $ clinicalbloodbank. Themaypresentwithallofthefollowing:willnottypecorrectly,antibodyscreen !\% stronglypositive,_crossmatches_Ԁstronglyincompatible,DATstronglypositive,eluatereactivewithallcells "8 & testedandlifethreateninganemia.h#!'$$   2.0  DirectAntiglobulinTest(DAT)%")$$ 0  0$$a.0$$TheDATshouldbeperformedwithavarietyofantiglobulinreagentstoclassifythecoatingprotein.&p$+$$ 0    b.0$$When_monospecific_ԀantiIgGandantiC3dreagentsareused,oneofthreepatternsofreactivitymay 'H%, befound:x( &-$$ 0  0$$0$$1)0 $$ 67%ofthecases,_RBCs_ԀarecoatedwithbothIgGandcomplement. P)&. $ $ 0  0$$0$$2)0 $$20%ofthecases,_RBCs_ԀarecoatedwithIgGalone.,*'/ $ $ 0  0$$0$$3)0 $$13%ofthecases,_RBCs_Ԁarecoatedwithcomplementalone.+(0 $ $  d. ,4 0  3.0$$SerumX$$ 0    a.0$$Thepatient'sserummaycontainverylittlefree_autoantibody_Ԁifthe_autoantibody_Ԁhasbeenprimarily  adsorbedbythepatient's_RBCs_Ԁinvivo.$$ _0    b.0$$_Autoantibody_Ԁusuallyappearsintheserumwhenallthespecificantigensitesonthe_RBCs_Ԁhavebeen 8 occupied,andnomoreantibodycanbeboundinvivo.InthiscasetheDATisusually strongly h positive .D$$ 0    c.0$$Approximately50%ofpatientswith_AIHA_Ԁwillhaveseracontaining_autoantibody_Ԁreactivewithall    cellstested,reagentaswellasdonor.The_autoantibody_ԀisusuallyIgGandisbestdemonstratedby  x  _IAT_. P $$ 0    d.0$$ Theserummaycontain_alloantibodies_Ԁinadditiontoautoantibodies. Itisveryimportantto X  identifyunderlying_alloantibodies_.4 $$ 0  4.0$$Eluate $$ 0    a.0$$ThepresenceoftheIgG_autoantibody_Ԁonthe_RBCs_Ԁcanbeconfirmedbyelution,usingthe_digitonin_ < acidtechniqueorwithorganicsolventssuchasetherorxylene.l$$ 0    b.0$$IgGmaybepresentatsuchlowlevelsthatnodetectableantibodyisrecoveredbyelution.$$ 0    c.0$$Ifonlycomplementisfoundcoatedtothe_RBCs_,theeluatewillhavenoserologicalactivity.t$$ 0  5.0$$Specificityofthe_Autoantibody_|$$$ 0    a.0$$Thespecificityofautoantibodiesassociatedwith_WAIHA_Ԁ isverycomplex. ,$$ 0    b.0$$ SpecificityisofteninitiallydirectedagainsttheRhantigencomplex.$$ 0    c.0$$ApartfromRhspecificity,therehavebeenotherreportsofwarmautoantibodieswithother < _specificities_Ԁ(refertotextbook).l $$ 0    d.0$$Itisrarely,ifever,necessarytoperformadditionaltestingtoascertain_autoantibody_Ԁspecificityin " ordertoselectantigennegativebloodfortransfusion.Insomepatients,simplespecificitywillbe # readilyapparent(_eg_,antie).Whenthereisevidenceofimmunehemolysisandthesimple  t$ _autoantibody_Ԁspecificityisclearcutnotrelativetheremaybesomebenefitinprovidingantigen !L% negativeblood.|"$ &$$ 0    e.0$$Itisimportant nottoexposethepatientstoRhantigensthattheirownredcellslack,especially ,$!( D. %")$$ 0    f.0$$Ifspecificityisdirectedatahighincidenceantigencompatibledonorbloodisunlikelytobefound. &`$+ Ifsuchbloodisavailable,itshouldbereservedfor_alloimmunized_Ԁpatientsofthatuncommon '8%, phenotype.h(&-$$ 0    g.0$$Thespecificityofwarmreactiveautoantibodiesisusuallyonlyofacademicinterest,unlessthepatient *'/ isactively_hemolyzing_Ԁandrequiresbloodtransfusion.*(0$$  P.+4   6.0  Detectionof_Alloantibodies_ԀinthePresenceofWarmReactiveAutoantibodies.X$$ 0    a.0$$Ifwarmreactiveautoantibodiesarepresentintheserum,itisimportanttoestablishthat  _alloantibodies_Ԁarenotalsopresentwhenthepatientconcernedrequiresblood_transfusion.s_$$ 0    b.0$$_Alloantibodies_Ԁmaynotbereadilyapparentfromtheresultsofinitialstudies;theirpresencemaybe 8 maskedbyautoantibodies.h$$     c.0  Itishelpfultoknowthebloodgroupphenotypeofthepatient'scellstoaidinpredictingwhat   _alloantibodies_Ԁtheymayhavenowormaymakeinthefuture.  $$ 0    d.0$$Whenthe_RBCs_ԀarecoatedwithIgG,_AHG_Ԁreactivereagentssuchasanti_Fya_oranti_Jka_cannotbeused  H  unlesstheIgGisremovedfromthe_RBCs_Ԁpriortotesting.Aprocedureforthis,involving _chloroquine_ x  diphosphate isfoundintheTechnicalManual.T $$     e.0  Autologousadsorption(_autoadsorption_) isthe bestwaytodetect_alloantibodies_Ԁinthepresence   ofwarmreactiveautoantibodies. ( MEMORIZETHISPROCEDURE ) $$ 0  0$$0$$1)0 $$At37C,invivoadsorptionwillhaveoccurredandallantigensitesonthepatient'sown_RBCs_ @ maybeblocked.Itisnecessary,therefore,toelute_autoantibody_Ԁfromthe_RBCs_Ԁtomakethe p sitesavailableforinvitro_autoadsorption_.Gentleheatelutionworksverywell.H $ $ 0  0$$0$$2)0 $$Treatmentoftheautologous_RBCs_Ԁwithproteolyticenzymesincreasestheircapacitytoadsorb  _autoantibody_.x $ $ 0  0$$0$$3)0 $$Patientserumisaddedtoanequivalentvolumeofpatientenzymetreatedcellsandincubated ( at1hourat37C.Duringthisincubationperiodantibodyinthepatientserumwillbeadsorbed X ontotheantigensonthepatientcells.0 $ $     0  ^^4)0 $$Theserum/cellmixtureisspundown,the"_autoadsorbed_Ԁserum"isremovedandtestedagainst  reagentscreencells.Interpretationofresultsisasfollows:` $ $   0  0 $$a)0| $ $all_RBCs_Ԁtestedgivenegativeresults,autoantibodyonlyh | $| $   0  0 $$b)0| $ $all_RBCs_Ԁtestedstillpositive,_autoabsorption_Ԁunsuccessful,repeatupto3times@!| $| $   0  0 $$c)0| $ $patternofposandnegreactions,alloantibodypresent,performapanelwith_autoadsorbed_ " serum.#| $| $ 0  0$$0$$5)0 $$ Thisprocedurecannotbeperformedonrecentlytransfusedpatients. Thepatientmayhave !H% anunderlying_alloantibody_,thetransfusedcellsmaypossesstheantigencausing_autoantibody_ |"$ &  and_alloantibody_Ԁtobeadsorbedout. T# ' $ $ 0  7.0$$TransfusionConsiderations%")$$ 0  0$$a.0$$ Itisbesttoavoidtransfusingpatientwhohave_AIHA_. &\$+$$ 0  0$$b.0$$Iftransfusionis essential , thesmallestvolumeof_RBCs_Ԁnecessarytomaintainadequateoxygen h(&- transportationshouldbegiven. D)&.$$ 0  0$$c.0$$Manytimesserologicallycompatiblebloodmaynotbeobtainable,andthereissubstantialriskthat *(0 concomitant_alloantibodies_Ԁcouldcauseaseverehemolytictransfusionreaction.+t)1$$   ,L*2 0  0$$d.0$$Theclinicalneed mustjustify theriskoftransfusion,butneededtransfusionsshouldnotbewithheld X becauseserologicallycompatiblebloodcannotbefound.Thedoctormustsignareleaseform 4 wheneverincompatiblebloodmustbegiven. $$  0  0$$e.0$$If_alloantibodies_Ԁhavebeenidentified,bloodlackingthecorrespondingantigen(s)shouldbeselected d fortransfusion.<$$ 0  0$$f.0$$Inmanycasesof_WAIHA_,no_autoantibody_Ԁspecificityisapparent;thepatient'sserumreactswithall D RBCsamplestestedtothesamedegree,orreactswith_RBCs_Ԁfromdifferentdonorstovaryingdegrees.    $$   0  ^^1)0 $$Insuchcases,someworkerstestalargenumberofdonorbloodsamples(_eg_,1220)withpatient  t  serum,orif_autoadsorption_Ԁwassuccessful,with_autoadsorbed_Ԁserum,andselectthoseunitsthat  L  givetheweakestreactionsinvitro.| $  $ $   0  ^^2)0 $$Therearenodatatoindicatebetterinvivosurvivalofthese" leastincompatible "units,but T  someworkersfeelmorecomfortableissuingtheleastincompatibleunits.0  $ $   0  ^^3)0 $$ItisbesttotransfusebloodofthesameRhphenotypeofthepatientifpossible.  $ $ 0  0$$g.0$$AlthoughRBCsurvivaloftransfusedcellsmaynotbenormal,transfusionwithincompatibleblood ` mayprovidesufficientoxygencarryingcapacityuntilothertherapycaneffectamorelastingbenefit.8$$ 0  0$$h.0$$Insummary,transfusionofpatientwith_WAIHA_Ԁshouldbeundertaken onlyifabsolutelyessential,  @ withtherealizationthatthebloodis nottrulycompatible anditseffectsarelikelytobebrief.$$ 0  0$$0$$1)0 $$Thevolumetransfusedshouldbethe leastamounttomaintainadequateoxygen x transportation .T $ $ 0  0$$0$$2)0 $$Anattemptshouldbemadeto differentiate_autoantibody_Ԁfrom_alloantibody_ intheserum. ` Ifspecificityisobvious, theappropriatedonorbloodshould,iffeasible,beselected.< $ $ 0  0$$0$$ 3) 0 $$Bloodshouldneverbewithheldfromapatientwithseverelifethreateninganemiabecause  ofincompatibilityduetoautoantibodies. t $ $ E.0  ColdAgglutininSyndrome(_CAS_),formerlycalledCold_Hemagglutinin_ԀDisease(_CHD_)|$ $$   1.0  Introduction,"$$ 0  0$$a.0$$_CAS_Ԁisthe mostcommontypeofhemolyticanemiaassociatedwithcoldreactiveautoantibodies,   $ andaccountsforapproximately16%ofallcasesofimmunehemolysis.!`%$$ 0  0$$b.0$$Itoccursasanacuteorchronicform.h#!'$$ 0  0$$0$$1)0 $$Theacuteformisoften secondaryto_lymphoproliferative_Ԁdisorders(_eg_,lymphoma)or %") Mycoplasmapneumoniaeinfection.%#* $ $ 0  0$$0$$ 2)0 $$Thechronicformisoftenseeninelderlypatientsandresultsinamildtomoderatedegreeof &t$+ hemolysis. _Raynaud_'sphenomenon and_hemoglobinuria_Ԁmayoccurincoldweather. 'L%, $ $ 0  2.0$$DirectAntiglobulinTestX)'.$$ 0  0$$a.0$$ Complementistheonlyglobulindetectedonthe_RBCs_.+(0$$   -<+3 0  0$$ b.0$$ ThecoldreactiveautoagglutininisIgMthatbindsto_RBCs_Ԁintheperipheralcirculationwhere X  thetemperaturemayfallto32C.IgMbindscomplementcomponentstothe_RBCs_Ԁatthis 4 temperature.Asthe_RBCs_Ԁreturntowarmerpartsofthecirculation,theIgMdissociates,   leaving_RBCs_Ԁcoatedonlywithcomplement .$$ 0  3.0$$Serum@$$ 0  0$$a.0$$IgMcoldreactiveautoagglutininsassociatedwithimmunehemolysisare usuallypresentattiters H greaterthan1000whentestedat4C.$ $$  0  0$$b.0$$Theyrarelyreactinvitroabove32Cintestswithsalinesuspended_RBCs_.However,if30%bovine  |  albuminisincludedinthereactionmedium,70%ofclinicallysignificantexampleswillreactat37C  T  (showhighthermalamplitude). , $$ 0  0$$c.0$$Antibodyscreeningtestsmaybeperformedstrictlyat37C(prewarmed).Thepatientsserum,screen 4  cellsandsalinetobeusedforwashingareallowedtowarmto37C.Serumisthenaddedtothecells    andincubatedfor1hour.Afterincubationthecellsare immediately washedwiththewarmsaline   andtakento_Coombs_.Ifapatternofreactivityisobserveda_prewarmed_Ԁpanelisdoneinthesame h manner.@$$ 0  4.0$$EluateH$$ 0  0$$a.0$$Ifthe_RBCs_Ԁhavebeencollectedandwashedat37C,noantibodyreactivitywillbefoundintheeluate,  asonlycomplementcomponentsarepresentonthe_RBCs_Ԁinvivoat37C.x$$ 0  0$$b.0$$_Eluates_ԀareusuallyonlydonewhentheDATispositivewithantiIgG.P$$ 0  5.0$$Specificityofthe_Autoantibody_ X$$ 0  0$$ a.0$$ Themostcommonspecificityassociatedwith_CAS_ԀisantiI.$$ 0  0$$b.0$$Lesscommonly,anti_i_Ԁisfound,usuallyassociatedwith infectiousmononucleosis. $$   6.0  Detectionof_Alloantibodies_ԀinthePresenceofColdReactiveAutoantibodies.@$$ 0  0$$a.0$$Potentcoldreactive_autoagglutinins_,likewarmreactiveautoantibodies,maymaskthepresencein H! serumofclinicallysignificant_alloantibodies_. "$$ 0  0$$b.0$$Ifthe_autoagglutinins_Ԁarereactiveat32C,oriftheybindcomplementto_RBCs_Ԁinthe_IAT_,itis  x$ advisabletoperforma cold_autoadsorption_ .( MEMORIZETHISPROCEDURE )!P%$$ 0  0$$^^1)0 $$Enzymetreatpatientcellstoenhanceadsorptionof_autoantibody_Ԁontothepatientcells.", & $ $ 0    ^^2)0 $$Allowtheserumspecimentoclotat4Cfor1hour.\#!' $ $ 0  0$$^^3)0 $$Addserumtoequivalentvolumeofpatient'sowncells.4$!( $ $ 0  0$$^^4)0 $$Incubateat4Cfor1hour. %") $ $   0  ^^5)0 $$Harvest_autoadsorbed_Ԁserumandtestagainstscreencells.Negativereactionswithallscreen %#* cellsisindicativeofnounderlying_alloantibody_.Positivereactionswithallthreescreencells &d$+ indicatestheneedforanadditional_autoadsorption_Ԁwithnewaliquotofcells(maximumof3 '<%, _autoadsorptions_Ԁcanbedone).If1or2ofthethreescreencellsispositiveperformapaneland l(&- identifyantibodyspecificity.D)&. $ $ 0  0$$^^6)0 $$_Autoadsorption_Ԁ cannotbeperformedonrecentlytransfusedpatients. *'/ $ $  X.,4 0  0$$c.0$$RabbitErythrocyteStromaTest(REST)X$$ 0  0$$0$$1)0 $$ItwasdiscoveredthatrabbitspossesstheIantigenontheir_RBCs_.Rabbitsarebledandtheir 0 _RBCs_Ԁ_hemolyzed_.Thecellsarewashedfreeofhemoglobinandputintoapreservativesolution. $ $ 0  0$$0$$2)0 $$Patientserumisaddedtothecellstromaandincubatedat4CtoadsorbouttheantiI. $ $ 0  0$$0$$3)0 $$Thismethodcanbeutilizedifthepatienthasbeenrecentlytransfused.` $ $ 0  0$$0$$4)0 $$Morethan1adsorptionmaybenecessary.8 $ $   7.0  SelectionofBloodforPatientswith_CAS_@$$ 0  0$$a.0$$Patientssufferingfrom_CAS_Ԁrarelyrequiretransfusion.  $$ 0  0$$b.0$$Iftheneedarises,compatibilitytestsshouldbeperformedinwaysthatminimizecoldreactive  H  _autoantibody_Ԁactivityyetstillpermitdetectionofclinicallysignificant_alloantibodies_.x $$ 0  0$$c.0$$Someworkersperformcompatibilitytestsstrictlyat37C.Thedonor_RBCs_Ԁandpatient'sserumare (  warmedto37Cpriortomixing,and_RBCs_Ԁarewashedwith37Csalineforthe_AHG_Ԁtest (_prewarmed_   technique) . $$ 0  0$$d.0$$Theuseofalbuminandotherpotentiatorsofagglutinationshouldbeavoided,sincetheseenhancethe 8 complementbindingpropertiesofthe_autoantibody_.h$$ 0  0$$e.0$$IgG_AHG_Ԁisusedforthe_AHG_Ԁtest.$$ 0  0$$f.0$$Ifthe_prewarmed_Ԁtechniquedoesnotworkperforman_autoabsorption_.p$$ 0  0$$g.0$$Bloodfortransfusionshouldbewarmedduringinfusionintothepatient.x $$ ,f  ,fF  .0    MixedType_AIHA_,f0ی($$ Ќ  0  1.0$$Introduction$$ 0  0$$a.0$$Thesepatientshavecoldagglutininsthathavelowtitersat4Cbuthighthermalamplitude.0$$ 0  0$$b.0$$Canbeidiopathicorsecondary,oftenassociatedwithsystemiclupuserythematosus.` $$ 0  0$$c.0$$Oftenpresentsasanextremelyacuteconditioncharacterizedbyverylowhemoglobinandcomplex 8! serumreactivitypresentinallphasesoftesting."$$ 0  2.0$$DirectAntiglobulinTest h$$$ 0  0$$a.0$$BothIgGandC3daredetectableonpatients_RBCs_.p" &$$ 0  0$$b.0$$IgGisduetowarm_autoantibody_ԀandC3dIboundbytheeffectsoftheIgM_autoantibody_.H# '$$ 0  3.0$$Serum$")$$ 0  0$$a.0$$BothwarmreactiveIgGandcoldreactiveIgMautoantibodiesarepresentresultinginreactivityat &P$+ allphasesofserumtesting.'(%,$$ 0  0$$b.0$$Coldagglutinintiteris lessthan64 at4C.X(&-$$ 0  0$$c.0$$Bothwarmandcoldautoabsorptionsmaybenecessarytodeterminethepresenceof_alloantibodies_.4)&.$$ 0  4.0$$EluatewillbereactiveduetothepresenceofIgG_autoantibody_.*(0$$ 0  5.0$$Specificityof_Autoantibody_,<*2$$ 0  0$$a.0$$Cold_autoantibody_Ԁmayhavetypicalspecificity,antiIor_i_,butoftenhasnoapparentspecificity.D.+4$$ 0  0$$b.0$$TheIgGwarm_autoantibody_Ԁisserologicallyindistinguishablefrom_specficities_Ԁencounteredin X _WAIHA_.0$$ 0  6.0$$SelectionofBlood$$ 0  0$$a.0$$Transfusionshouldbeconsideredcarefully,especiallysincepromptcorticosteroidtherapyis 8 frequentlysuccessful.h$$ 0  0$$b.0$$Transfusionmayresultinincreasedhemolysis,whichmaybelifethreatening. $$ 0  0$$c.0$$Considerationsforbloodselectionisidenticaltothatfor_WAIHA_Ԁand_CAS_. p $$ G.0  ParoxysmalCold_Hemoglobinuria_Ԁ(_PCH_)x $$   1.0  Introduction( $$ 0    a.0$$Thisisthe rarest formofautoimmunehemolyticanemia. $$ 0    b.0$$_PCH_Ԁpresentsasanacutetransientconditionsecondarytoviralinfections,particularlyinyoung 4 childrenorasanidiopathicchronicdiseaseinolderpeople.d $$ 0    c.0$$Itismarkedbyepisodesof_hemoglobinemia_Ԁand_hemoglobinuria_Ԁafterexposuretothecold.$$   2.0  DirectAntiglobulinTestl$$ 0    a.0$$The_autoantibody_Ԁin_PCH_Ԁisan IgG protein.LikeIgMcoldreactive_autoagglutinins_, theIgG t _autoantibody_Ԁin_PCH_Ԁreactswith_RBCs_Ԁincolderpartsofthebody,causescomplement P componentstobeboundirreversiblyto_RBCs_,andtheIgG_elutes_Ԁoffatwarmertemperatures ( inthebody. $$ 0    b.0$$Consequently,complementonlyisdetectedonthe_RBCs_.X$$   3.0  Serum` $$ 0    a.0$$TheIgG_autoantibody_Ԁin_PCH_Ԁis_clasically_Ԁdescribedasa _biphasic_Ԁ_hemolysin_ ,sinceitbindsto_RBCs_ " atlowtemperaturesandthencauseshemolysiswhenthecoated_RBCs_Ԁarewarmedto37C.Thisisthe # basisofthediagnostictestforthedisease, the_Donath_Ԅ_Landsteiner_Ԁtest . l$$$ 0  0$$b.0$$The_autoantibody_Ԁoftenagglutinatesnormal_RBCs_Ԁat4C, butrarelytotitersgreaterthan64 .x" &$$ 0  4.0$$Eluate,$!($$ 0    a.0$$Asin_CHD_,onlycomplementcomponentsarepresenton_RBCs_Ԁinvivoat37C.%#*$$ 0    b.0$$Consequently,_eluates_Ԁpreparedfrom_RBCs_Ԁofpatientswith_PCH_Ԁareinvariably_nonreactive_.'4%,$$ 0  5.0$$Specificityofthe_Autoantibody_<)&.$$ 0    a.0$$The_autoantibody_Ԁof_PCH_Ԁhasmostfrequentlybeenshowntohave antiP specificity.*(0$$ 0    b.0$$Theantibodyreactswithall_RBCs_Ԁ(includingthepatients)exceptthoseoftheveryrareporPk ,H*2 phenotypes.x- +3$$  P.+4 0  6.0$$Detectionof_alloantibodies_Ԁwhichmaybemaskedbyautoantibodiesin_PCH_Ԁisthesameasthatdescribed X for_CHD_Ԁexceptonlycoldautoadsorptionmaybedone.TheRESTprocedureonlyremovesantiI.So 0 ifapatienthasbeenrecentlytransfused,_autoabsorption_Ԁcannotbedone.$$ 0  7.0$$Selectionofbloodforpatientswith_PCH_.`$$ 0    a.0$$Serafrompatientswith_PCH_Ԁwillbecompatiblewithrandomdonor_RBCs_Ԁwhentestedbyroutine h _crossmatch_Ԁprocedures.@$$ 0    b.0$$Thecausativeantibodyrarelyreactsasanagglutininabove4C.  $$ 0    c.0$$Whilethereissomeevidencethatp_RBCs_Ԁsurvivebetterthan_RBCs_ԀofacommonPsystemphenotype,  H  theincidenceofpbloodisapproximately1in200,000.x $$ 0    d.0$$_PCH_Ԁpatientsoftenrequiretransfusionbeforerarebloodcanbeobtained,andthetransfusionof (  randomdonorbloodshouldnotbewithheldforpatientsrequiringurgenttransfusions. $$ 0    e.0$$Rarepbloodshouldbeconsidered only forthosepatientswhodonotrespondtorandomdonorblood.X$$ ,f  ,fH  .0    DrugInducedInVivoRBCSensitization,fیd $$ Ќ  0  1.0$$Introduction$$ 0  0$$a.0$$Drugssometimesinducetheformationofantibodies,eitheragainstthedrugitselforagainstintrinsic l RBCantigens.D$$ 0    b.0$$Mostdrugshaveamolecularweightsubstantiallybelowthe5000_dalton_Ԁlevelusuallyconsideredto L bethethresholdforeffective_immunogenicity_.$$$ 0    c.0$$Drugsactas_haptens_,elicitingantibodyonlyaftertheyhavebeenfirmlyboundtoaproteincarrier.|$$ 0    d.0$$Onceformed,theantibodycanreactwiththesmall_hapten_Ԁindependentofanyproteinattachment.,$$ 0    e.0$$DrugsmaycauseapositiveDAT,whichmayormaynotbeassociatedwithimmunehemolysis,by 4! oneoffourmechanisms. "$$   2.0  DrugAdsorption(DA) d$$$   0  a.0$$Approximately3%ofpatientsreceivinglargedosesofpenicillinIV(_eg_,millionsofunitsperday)and l" & cephalosporinswilldevelopapositiveDAT,butlessthat5%ofthesewilldevelophemolyticanemia.D# '$$ 0    b.0$$_Intravascular_Ԁhemolysisis rare .$")$$ 0  c.0$$ThemechanismofthepositiveDATisclear.&P$+$$ 0  0$$^^1)0 $$Thepenicillinisadsorbedtothe_RBCs_Ԁinvivo.'(%, $ $ 0  0$$^^2)0 $$Ifthepatienthasformedantibodiestopenicillin,theantipenicillinwillreactwiththepenicillin X(&- boundtothe_RBCs_.0)&. $ $ 0  0$$^^3)0 $$Thisresultsinpenicillincoated_RBCs_ԀbecomingcoatedwithIgG.*'/ $ $ 0  0$$^^4)0 $$Complementisnotusuallyinvolved.Ifhemolysisoccurs,_RBCs_Ԁaredestroyedextravascularly, *(0 probablyinthesamewaythat_RBCs_ԀcoatedwithIgG_alloantibodies_Ԁaredestroyed.+`)1 $ $  @.+4   0  d.0$$Theclinicalandlaboratoryfeaturesofpenicillininducedhemolysisare:X$$ 0    ^^1)0 $$TheDATisstronglypositiveduetoIgGcoating. $ $ 0  0$$^^2)0 $$Unless_alloantibodies_Ԁarepresentcoincidentally,screeningtestsforunexpectedserumantibodies ` willbe_nonreactive_.8 $ $ 0  0$$^^3)0 $$Antibody_eluted_Ԁfromthe_RBCs_Ԁwillreactwithpenicillincoated_RBCs_Ԁbutnotwith_uncoated_ @ _RBCs_.  $ $ 0  0$$^^4)0 $$AhightiterIgGantibodytopenicillinisalwayspresentintheserum. p  $ $ 0  0$$^^5)0 $$HemolysistypicallydevelopsonlyinpatientsreceivingverylargedosesofIVpenicillin.x  $ $ 0  0$$^^6)0 $$Hemolysisissubacuteinonset,butmaybelifethreateningiftheetiologyisunrecognizedand (  penicillinadministrationiscontinued.  $ $ 0  0$$^^7)0 $$Discontinuationofpenicillintherapyisusuallyfollowedbycessationofhemolysis.However, X hemolysisofdecreasingseveritymaypersistforweeks.0 $ $ 0  3.0$$ImmuneComplex(IC)Adsorption8$$ 0    a.0$$Somedrugsdonotbinddirectlyto_RBCs_,buthaveahighaffinityfortheirspecificantibodiesand  formantigenantibodycomplexesthatcirculateintheplasma.h$$ 0    b.0$$Theseimmunecomplexesattachnonspecificallyto_RBCs_Ԁandinitiatecomplementactivationofthe p RBCsurfacewhichmayleadto _intravascular_Ԁhemolysis. H$$ 0    c.0$$_RBCs_Ԁthatarenot_hemolyzed_ԀhaveapositiveDATbecauseofcomplementcoating,but  immunoglobulinmayalsobebound.|$$ 0    d.0$$Theimmunecomplexesmaydissociateafteractivatingcomplementandgotoreactwithother_RBCs_. , Thismayexplainwhysmallamountsofthedrugcaninduceacutehemolyticepisodes.\ $$ 0    e.0$$Thismechanismistheone leastoftenencountered wheninvestigatingdruginducedhemolysis. "$$ 0    f.0$$Thecharacteristicfindingsare: h$$$ 0  0$$0$$1)0 $$Acute_intravascular_Ԁhemolysiswith_hemoglobinemia_Ԁand_hemoglobinuria_Ԁistheusual p" & presentation.Renalfailureoccursinapproximately50%ofthecases.H# ' $ $ 0  0$$0$$2)0 $$Onceantibodyhasbeenformed,thepatientmayexperienceseverehemolyticepisodesafter  $!( takingonlysmallquantitiesofthedrug.$") $ $ 0  0$$0$$3)0 $$TheantibodycanbeeitherIgMorIgG.%x#* $ $ 0  0$$0$$4)0 $$The_RBCs_Ԁareoftencoatedonlywithcomplement.&P$+ $ $ 0  0$$0$$5)0 $$Invitroreactionssuchasagglutination,hemolysisandreactive_IATs_Ԁcanonlybedemonstrated '(%, whenthepatient'sserumandreagent_RBCs_Ԁareincubatedinthepresenceofthedrug.X(&- $ $  @.+4 0  4.0$$MembraneModificationX$$ 0  0$$a.0$$DrugsofthecephalosporinsaretheonlydrugsthatarethoughttoalterRBCmembranesinsucha  waythatthe_RBCs_Ԁadsorballproteinsinanonspecificmanner.Whenthisoccursinvivoitcancause  apositiveDAT.`$$ 0    b.0$$Inadditiontothisnonimmuneadsorptionofproteins,thecephalosporinscanalsoinduceapositive h DATbythemechanismdescribedforpenicillin.@$$ 0    c.0$$Thedrugbindsfirmlyto_RBCs_,whichtheninteractwiththespecific_anticephalosporin_Ԁantibody.  $$ 0    d.0$$Approximately4%ofpatientsreceivingcephalosporinsdevelopapositiveDAT. H $$ 0    e.0$$Therehavebeenoccasionalreportsofhemolysisresultingfromcephalosporintherapy;theseare P  thoughttoresultfromtheeffectofspecific_anticephalosporin_Ԁantibodies,ratherthanfrom (  _nonimmunologic_Ԁadsorptionofproteinsfollowingmembranemodification. $$ 0  5.0$$InductionofAutoimmunityX$$ 0    a.0$$Thefirstcasesof_WAIHA_Ԁresultingfrom alpha_methyldopa_Ԁ (_Aldomet_,_Aldoclor_,_Aldoril_)therapy ` weredescribedin1966.:$$ 0    b.0$$Followingalpha_methyldopa_Ԁtherapy,autoantibodiesareformedthatreactwithintrinsicRBC  antigens.Theydonotreactwiththedruginvitro,eitherdirectlyorindirectly.j$$ 0    c.0$$Theserologicalfindingsare indistinguishable fromthoseassociatedwith_WAIHA_;often,the r _autoantibody_ԀcanbefoundtohaveanRhrelatedspecificity.N$$ 0    d.0$$IthasbeensuggestedthatthedruginterfereswithsuppressorTcellfunctionallowingoverproduction  of_autoantibody_ԀbyBcells.~$$ 0    e.0$$ Therapywithalpha_methyldopa_Ԁaccountsformorecasesofdruginducedpositive_DATS_Ԁand . immunehemolysisthanalloftheotherdrugs. b  $$ 0    f.0$$Theclinicalanlaboratoryfeaturesareasfollows:"$$ 0  0$$0$$1)0 $$Positive_DATs_Ԁoccurinapproximately15%ofpatientsreceivingalpha_methyldopa_.Only0.5  j$ 1.0%ofpatientstakingalpha_methyldopa_Ԁdevelophemolyticanemia.!B% $ $ 0  0$$0$$2)0 $$_RBCs_ԀareusuallycoatedonlywithIgG,butoccasionallyweakcomplementcoatingisalso r" & present.J# ' $ $ 0  0$$0$$3)0 $$TheDATusuallybecomespositiveonlyafter36monthsoftherapy."$!( $ $ 0  0$$0$$4)0 $$DevelopmentofapositiveDATisdosedependent;approximately36%ofpatientstaking3g $") ofthedrugdailydevelopapositiveDATcomparedwith11%ofpatientsreceiving1gperday.%z#* $ $ 0  0$$0$$5)0 $$Antibodiesintheserumandonthe_RBCs_Ԁareindistinguishablefromthosefoundinidiopathic &R$+ _WAIHA_.'*%, $ $ 0  0$$0$$6)0 $$ThestrengthofthepositiveDATbecomesprogressivelyweakeroncealpha_methyldopa_Ԁtherapy Z(&- isdiscontinued.Thismaytakefrom1monthto2years.Inpatientswithhemolyticanemiadue 2)&. toalpha_methyldopa_Ԁtherapy,hematologicvaluesusuallyimprovewithinthefirstweekorso  *'/ afterthedrugtherapyisdiscontinued.*(0 $ $  B.+4 I%  .0  LaboratoryInvestigationofDrugInducedHemolysisX$$   1.0  Introduction$$ 0    a.0$$Thedrugrelatedproblemsmostcommonlyencounteredinthebloodbankarethoseassociatedwith ` apositiveDAT,andalpha_methyldopa_Ԁisbyfarthemostcommoncauseofadruginducepositive 8 DAT.h$$ 0    b.0$$Drugsofthealpha_methyldopa_Ԁgroupmaycausereactive_IAT_Ԁinserum/redcellmixtureswithout   addeddrug.  $$   2.0  Theserologicalevaluationofdruginducedhemolysisiscarriedoutinessentiallythesamemannerasthat  H  toinvestigate_AIHA_.x $$ 0    a.0$$_Monospecific_ԀantiglobulinseraareusefulfortheDAT.( $$ 0  0$$0$$1)0 $$DrugsthatcauseapositiveDATbytheimmunecomplexmechanismprimarilybind   complementto_RBCs_.X $ $ 0  0$$0$$2)0 $$Penicillinoralpha_methyldopa_ԀcauseIgGtobeboundtothe_RBCs_.0 $ $ 0  0$$0$$3)0 $$Redcellsthathaveadsorbedproteins_nonimmunologically_Ԁinassociationwithdrugsofthe ` cephalosporingroupreactwithsomeorallantiglobulinsera.8 $ $ 0  0$$b.0$$Thepatient'sserumshouldbetestedforunexpectedantibodiesbytheroutineproceduresusedin  _pretransfusion_Ԁtesting.h$$ 0  0$$0$$1)0 $$Iftheserumdoesnotreactwithuntreated_RBCs_,thetestsshouldberepeatedagainstABO p compatible_RBCs_Ԁinthepresenceofanydrugthatthepatienthasbeenreceiving.H $ $ 0  0$$0$$2)0 $$Techniquesfortestingmaybethosedescribedinpublishedcases,ifthedrugisonealready   reportedasbeing_immunogenic_. $ $ 0  0$$c.0$$Ifthesetestsarenotinformative,anattemptshouldbemadetocoatnormal_RBCs_Ԁwiththedrug,and P testthepatient'sserumandaneluatefromthepatient's_RBCs_Ԁagainstthedrugcoatedcells.($$ 0  0$$0$$1)0 $$Thisisthemethodofchoicewhenpenicillinorthecephalosporinsarethesuspectedcauseof 0! thepositiveDAT." $ $ 0  0$$0$$2)0 $$ThedefinitivetestresultforapenicillininducedpositiveDATisapositive_IAT_Ԁwiththeeluate # andpenicillincoated_RBCs_Ԁbutnotwiththeeluateanduntreated_RBCs_. `$ $ $ 0  0$$0$$3)0 $$DrugsthatinduceapositiveDATbytheimmunecomplexmechanismoftenbindonly !8% complementto_RBCs_,sothattheeluatemaybe_nonreactive_,evenwhenthedrugisaddedtothe h" & testsystem.@# ' $ $  %&]  Exam6_Online_ %p#* DiscussLaboratoryPractical #&]% Ɯ#