BREATH TESTING IN INTESTINAL DISACCHARIDASE DEFICIENCY SIBO.docx
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BREATHTESTINGININTESTINALDISACCHARIDASEDEFICIENCYSIBO
BREATHTESTINGININTESTINALDISACCHARIDASEDEFICIENCYANDBACTERIALOVERGROWTHOFTHESMALLINTESTINE
ByLee,MartinJ.,Barrie,Stephen,JournalofNutritional&EnvironmentalMedicine,13590847,Mar96,Vol.6,Issue1
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Thebreakdownandabsorptionofnutrients,akeyfunctionofthedigestivesystem,isimpairedincarbohydratemaldigestionandbacterialovergrowthofthesmallintestine.Theresultingcontinuousirritationoftheintestinalmucosamayhaveasystemicimpactandleadtochronicconditionsandincreasedsusceptibilitytoparasiticinfections.Precisediagnosisisthereforeofgreatimportance.Traditionalmethodsareinvasive,requirelargechallengedosesor,asineliminationdiets,donotprovidedefinitivediagnosis.Measurementofhydrogenandmethanelevelsinalveolarsamplescollectedfollowingacarbohydratechallengeissimple,non-invasiveandprovidesgoodsensitivity,andspecificity. Breath testscanfurtherdefinitivelydemonstratelactosemaldigestion,differentiateothercarbohydrateintolerancesandallowdeterminationofseverityofcarbohydrateintolerance.Percentagesoffalse-negativeandfalse-positivesarelowcomparedtotraditionalmethodswheninstructionsarefollowedproperly.Technicaladvancesincollectionandanalysishavegreatlysimplified breath tests.Advantagesofbreath testing forpractitionersandpatientsmakethisapromisingtechniqueforfutureapplications.
Keywords breath testing,lactoseintolerance,bacterialovergrowth,disaccharidasedeficiency,carbohydrateintolerance,maldigestion,intestinalmicroorganisms.
INTRODUCTION
Thedigestivesystemplaysamajorroleinthebody'stotalhealth,startingwiththeproperbreakdownandabsorptionofnutrientsthatfuelthecells.Carbohydrateintolerancesandbacterialovergrowthaffectthetotalpictureofdigestivefunctioning.Thesedisordersareassociatedwithcontinuousirritationoftheintestinalmucosa,leadingtointestinaldysbiosisandgrowthofimbalancedbacterialflora.Lossofepithelialintegrityaffectstheabsorptionofantigens,possibleallergensandbacterialbreakdownproducts.Alteredpermeabilityduetomucosaldamagemaybringforthseeminglyunrelatedconditionsincludingheadaches,foodallergiesandsusceptibilitytoparasiticinfections.Chronicdisorders,suchasarthritis,migraineheadaches,asthmaorchronicfatigue,maydevelopassequelaetotheburdenofgastrointestinaltoxinsandantigenicstimulation[1,2].
Toavoidlong-termconsequencesofdigestivealterations,theastuteclinicianmustinvestigatetheunderlyingcausesofintestinalsymptomsusingreliable,sensitiveandspecific testing methodsforaccuratediagnosisandtreatmentmonitoring.Measurementofhydrogenandmethaneinalveolarsamplessatisfiestheserequirementsandhasbeenappliedtothediagnosisofcarbohydrateintolerancesandbacterialovergrowthofthesmallintestine.
Principlesof Breath Testing
Sincebacteria,primarilyanaerobicbacteria,canproducehydrogenandmethane,thepresenceofthesegasesindicatesthatcarbohydrateshavebeenexposedtobacterialfermentation.Someofthegasesproducedareabsorbedintothebloodstreamandtraveltothelungsthroughthepulmonaryalveolarmembrane,wheretheycanthenbedetectedin breath samples[3].
Hydrogen/methane breath testsforcarbohydrateintolerancesandbacterialovergrowthinvolvecollectionofabaselinefasting breath sampleandaseriesof breathsamplestakenafterachallengeofcarbohydrates.Thetypeanddoseofchallengeandcollectiontimesdependontheconditionunderinvestigation. Breath testing,doneathomeorinthephysician'soffice,isconvenientforthepatient,asrepeated breath samplingissimple,non-invasive,inexpensiveandwelltolerated[4,5].
Normal Breath HydrogenandMethane
Fornon-fastingindividuals,the breath hydrogenlevelishighearlyinthemorning.Hydrogenaccumulatesbecauseofreducedmotilityduringsleepwhenfoodisexposedtobacteriainthecolonforlongerperiodsoftime.Also,hypoventilationtypicalduringsleepincreasesthelevelofhydrogeninthebloodandalveolarairbecauseitisnoteliminatedefficiently.The breath hydrogenlevelfallsduringthemorninguntilearlyafternoon,whenitincreasesslightlyuntilmid-afternoon,probablyduetotheeffectsofcarbohydratesreachingthecolonfromlunchmeals. Breath hydrogenfallsgraduallyfortherestoftheday.Infastingindividuals, breath hydrogenfallssteadilyduringtheentireday,reflectingthedecreasingavailabilityofcarbohydratestogeneratehydrogen[6].
Inordertounderstand breath gas testing completely,itisimportanttoconsidermethaneinadditiontohydrogenproduction.Whileexcretedindependently,methaneexistswithhydrogeninarelationshipwhichisonlypartiallyunderstood[7,8].Methanogenicbacteriaconverthydrogentomethaneinthecolon.Therefore,bacterialmetabolismofdisaccharidesmayleadtoanincreaseineitherhydrogenormethaneorbothgases. Testing forbothtracegasesreducesthenumberoffalse-negativeresponsesandincreasestheaccuracyofthetestintheminorityofindividualswhodonotproducehydrogeninresponsetocarbohydratechallenges[3,9,10].
Methodology
Previously, breath testing wasavailableonlytophysicianswhoownedagaschromatographandwhowerewillingtotestpatientsforhoursintheiroffices.Technologicaladvanceshavesimplifiedcollection,storageandanalysisof breath samples.Vacuum-sealedtubesareusedforcollectionandstorageofalveolarbreath samples.Usingamouthpiece,patientsexhaleintothetubesandpuncturetheself-sealingmembrane(Fig.I).Duringshippingforlaboratoryanalysisthetubeskeepintactthe breath trace-gasespresentinthesamples[11].Analyzersspecificallydesignedfordeterminationof breath gasesreducethecostandanalysistime.Themeasurementofhydrogenandmethaneisbasedongaschromatographicseparationandelectrochemicaldetectionthroughasolid-statesensorspecificforreducinggases[12,13].
Precautions
False-positiveorfalse-negativeresultsareeasilyavoidedbyfollowingafewsimpleguidelines.Foodslowinnon-starchpolysaccharidesshouldbeeatenthedaypreceding breath samplecollectionandfibersupplementsshouldbediscontinued,asnon-starchpolysaccharidesinthecolonatthebeginningofthetestleadtoincreasedbaseline breath hydrogenandthereforedecreasethesensitivityofthetest[14,15].Smokingintheareawheresamplesarecollectedmayproducehighhydrogenlevelsandunstablebaselineresults[16].Sleepingduringthetestalsoleadstofalse-positiveresults,astheslowdowninremovalof breath trace-gasesfrombloodleadstoincreasedhydrogenandmethanelevels[6].Reducedtransittime,asseenindiabetesandfollowinggastricsurgery,willalsoleadtofalselyelevatedresults,asbacterialfermentationinthecolonmaybemisinterpretedassmallintestinalgasproduction[17].
False-negativeresultscanbecausedbytheuseofantibioticspriortothetest[18,19],theuseoflaxativesorenemaswhichdecreasehydrogenandmethaneresponseinmalabsorbersandcreatereducedfermentationinthecolon,andseverediarrhea[20].Hyperacidityalsoinhibitsthegenerationofhydrogenandresultsinmethaneproductionbycolonicbacteriainadditiontoorinsteadofhydrogen[21,22].
LACTOSEINTOLERANCE
Themajorityoftheworld'spopulationislactasedeficienttosomedegree(Table1).Inthissociety,lactoseintoleranceisthemostprevalenttypeofcarbohydrateintolerancebecausemilksugarisverycommoninatypicaldiet.Withoutthelactaseenzyme,theintestinecannotbreaklactosedownintoglucoseandgalactose.Lactaseproductionisgeneticallydeterminedasadominanttrait.Maximumenzymelevelsarereachedinthehumanintestineshortlyafterbirthanddeclineaftertheageof3to31/2[6].Morethan50millionAmericanscannotadequatelyhydrolyzelactose[23].Theypresentwithsymptomsofnon-ulcerativedyspepsiaandirritablebowelsyndrome,suchasbloating,diarrhea,flatulence,abdominalcrampsanddiscomfort[24,25].
Lactosemaldigestionisfrequentlyrecognizedforthefirsttimeinolderpatients,possiblybecausetheyaremoresensitivetointestinalproblems.Theymayhaveenduredgasandothersymptomsforyearswithoutconnectingthesymptomstotheirdiet[3].Adultonsetlactasedeficiencymayresultfromconditionsthatdamagetheintestinallining,suchasinfectiousdiarrhea,intestinalparasitesorinflammatoryboweldisease.Alcoholism,malnutrition,pelvicradiationtherapyanddrugssuchasantibioticscanalsotriggerlactosemaldigestion[26].
Precisediagnosisoflactosemaldigestionisveryimportantsincemanypeopleneverrelatetheirintestinalsymptomstotheirdietandcontinueeatingfoodstheycannotdigestproperly[5,23].Inonestudy,42%oflactose-intolerantpatientsdidnotassociatetheirsymptomswithanyparticularfood[27].Attimes,individualsmayevenmisleadtheirphysiciansbydenyingaconnectiontotheirsymptomsandtheirdiet[27,28].Alactosetolerancetestcandramaticallydemonstratetheconnectionbetweensymptomsanddiettopatients,andemphasizetheimportanceoffollowingdietrestrictions[28].
Ontheotherhand,patientsmaybeunnecessarilyavoidingdairyproducts.Sincemilkanddairyproductsareimportantsourcesofcalciumandvitamins,particularlyforchildren,pregnantwomen,nursingmothersandolderadults,theyshouldnotbeeliminatedfromthedietwithoutgoodreason[5,29].
Precisediagnosisfurtheravoidsmisdiagnosisofmilkallergy.Individualswhodonotproducesufficientquantitiesoflactasearenotnecessarilyallergictom
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