Protective effect of metformin against tuberculosis infections in diabetic patients: an observational study of south Indian tertiary healthcare facility

w w w . e l s e v ie r . c o m / l o c a t e / b j i d

The

Brazilian

Journal

of

INFECTIOUS

DISEASES

Original

Article

Protective

effect

of

metformin

against

tuberculosis

infections

in

diabetic

patients:

an

observational

study

of

south

Indian

tertiary

healthcare

facility

Srujitha

Marupuru

_,

_Padmanav

_Senapati

_,

_Swathi

_Pathadka

_,

_Sonal

_Sekhar

_Miraj

_,

Mazhuvancherry

Kesavan

Unnikrishnan

_,

_Mohan

_K.

_Manu

a_{ManipalUniversity,ManipalCollegeofPharmaceuticalSciences,DepartmentofPharmacyPractice,Manipal,India} b_{ManipalUniversity,KasturbaMedicalCollegeHospital,DepartmentofPulmonaryMedicine,Manipal,India}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received6November2016 Accepted23January2017 Availableonline13February2017

Keywords:

Diabetes Metformin

Tuberculosisprevention

a

b

s

t

r

a

c

t

Background:WorldHealthOrganizationestimatedthatpeoplewithdiabetes(DM)areat 2–3timeshigherriskfortuberculosis(TB).StudieshaveshownthatDMnotonlyincreases theriskofactiveTB,butalsoputsco-affectedpersonsatincreasedriskofpooroutcomes.

Objectives:TodeterminetheprotectiveeffectofmetforminagainstTBinDMpatientsand also,toinvestigatetherelationshipbetweenpoorglycemiccontrolandTB.

Methods:Acase–controlstudy wasconductedover8 months,where casesandcontrols wereselectedbasedontheinclusionandexclusioncriteriaofthestudy.Thediabetics diag-nosedwithTBwereselectedasstudygroup(SG=152)andwithoutTBwereascontrolgroup (CG=299).Exposurestatusofmetformininbothgroupswereanalyzed.

Results:Themean(SD)ageofbothCGandSGwere55.54±11.82and52.80±11.75, respec-tively.Majorityofthesubjectsinthestudyweremales.ThemeanhospitalstayofSGandCG were7daysand6days,respectively.Poorglycemiccontrol(HbA1c>8)observedinSG(51.7%) vsCG(31.4%).HbA1cvalue<7isassociatedprotectivefactorforTBoccurrence[OR=0.52 (95%CI0.29–0.93)].TheprotectiveeffectofmetforminagainstTBwas3.9-foldindiabetics (OR=0.256,0.16–0.40).

Conclusion:PoorglycemiccontrolamongdiabeticsisariskfactorforTBoccurrence.The resultshowsmetforminuseisaprotectiveagentagainstTBinfectionindiabetics.Hence, incorporationofmetforminintostandardclinicalcarewouldofferatherapeuticoptionfor thepreventionofTB.

©2017SociedadeBrasileiradeInfectologia.PublishedbyElsevierEditoraLtda.Thisisan openaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/ by-nc-nd/4.0/).

∗ _{Correspondingauthor.}

E-mailaddresses:sonalsekhar@gmail.com,sonal.sekhar@manipal.edu(S.S.Miraj).

http://dx.doi.org/10.1016/j.bjid.2017.01.001

1413-8670/©2017SociedadeBrasileiradeInfectologia.PublishedbyElsevierEditoraLtda.ThisisanopenaccessarticleundertheCC BY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Tuberculosis(TB)isoneofthemostcommoninfectious dis-easescausingmorbidityandmortalityworldwide.Eachyear, approximately9.6millionnewcasesand1.5milliondeaths occurduetoTB.1,2_{IndiahasthehighestburdenofTB.}3_More

than95%ofTBdeathshappeninresource-poorlowand mid-dle incomecountries. Persons with compromisedimmune states,suchasHIVinfection,diabetes,tobaccouse,and mal-nutritionare atagreaterriskofprogressingfrom latentto activeTB.2_{Itispossiblethatinareasofhighprevalenceof}

dia-betes,theimpactoftheDMepidemicontuberculosiscouldbe asgreatasthatofHIV.

Globally, around 15% of TB cases are estimated to be attributabletoDM.4_{Theescalationofdiabetesprevalencein}

TB-endemicregionsmayadverselyaffecttuberculosiscontrol. The current Indian diabetes scenario could lead to resur-genceofTBinendemicregions,especiallyinurbanareas.5

DiabeticpatientswithTBhavenegativetreatmentoutcomes suchasdelayinsputumcultureconversion,increasedriskof deathduringtreatment,andTBrelapseaftersuccessful anti-tuberculartreatment regimen.2 _{Diabetic TBpatients suffer}

fromhighermortality(7.5%)comparedtopatientswitheither TB(1%)orDM(2%)alone.6AstudyfromKerala(Southernmost stateofIndia)demonstratedthatdiabeticswithdrugsensitive TBhavegreaterprobabilityoffailingfirstlineTBtreatmentas comparedtothosewithoutDM.7,8

Diabetesisassociatedwithdiminishedinnateandadaptive immuneresponseswhichareessentialtocombatthe intracel-lularproliferationofMycobacteriumtuberculosis(M.tb).Hostcell recognitionisdiminishedindiabetics,resultinginthedecline ofimmuneresponse,whichrenderdiabeticsmore suscepti-bletobacterial infections.ControlofTBcomprisesvarious strategiessuchascasetreatment,preventivetherapy,and vac-cinationwithBCG.9_{TBpreventionandcontrolcouldbefurther}

improvedbyinterventionsthatcounterknownriskelements ofTBsuchasdiabetes,immunecompromiseinconditionslike HIV.

Currently, there are a number of difficulties in devel-oping new drugs with potential anti-TB effects, especially withtherapeuticand prophylacticefficacyagainstdormant

M.tborganisms.Thecurrentanti-tuberculartherapyislong drawn and is associated with drug toxicity and height-enedmulti-drugresistance.Therapeuticmodulationofhost cellresponsesthatenhances pathogeneradicationisbeing suggestedasanewparadigmindrugdiscovery.These ‘host-targeted’ therapeutic strategies are less likely to provoke microbialresistancethantargetingpathogenswith conven-tionaldrugs.

Innate antimicrobial arsenal of the host cell includes reactiveoxygenspecies(ROS)and reactivenitrogenspecies (RNS),inadditiontothephagosomalmachineryorautophagy. Autophagyiscontrolledbymammaliantargetofrapamycin (mTOR)complex-1andadenosinemonophosphateactivated protein kinase (AMPK).10,11 _{Singhal et al. demonstrated}

that AMPK-activation by metformin inhibits intracellular growth ofM. tb, restricting disease immunopathology, and enhancingtheefficacyofconventionalanti-TBdrugs. Sing-hal’s data suggest that both protective immunity and

pathological immunitycanbeindependentlymodulatedby metforminduringM.tbinfectionbyenhancingM.tb-specific

host immunity, reducing inflammation, promoting disease resolution,andimprovingtreatmentoutcomes.Atthecellular level,metformindifferentiallyaffectsimmuneresponseand inflammationthroughdifferentmechanisms.Theprotective effectismediatedbyincreasedhostcellproductionofmROS and increased acidification of mycobacteriod phagosome. Actually,mROSproduceduponmitochondrialrecruitmentto phagosomesisinstrumentalinkillingofintracellularbacteria bymacrophages.Theanti-inflammatoryeffectismediatedby activationofAMPK.Metforminalsopromotestheexpansionof

M.tbspecificIFN-␥-secretingCD8+Tcellsinuninfectedmice indicatingthatmetforminhasanimpactonthelungimmune cells independently ofcurrentinfections.These effectsare consistentwithmetformin-inducedexpansionofCD8+ mem-oryTcells,anotherknownconsequenceofAMPKactivation. Both CD4+ andcytotoxic T cellsare key tocontrolling pri-maryM.tbinfectioninhumansubjects.StudiesbySinghal etal.havealsoshownanincreaseinM.tb-specificTcellsin metformintreateddiabeticpatientswithlatentTB.Metformin therapycombinedwithstandardTBtreatmentregimenshas demonstratedbeneficialclinicaloutcomesinactiveTB.

We hypothesize that metformin, via AMPK-activation, boostshostimmunityandtherebyprotectDMpatientsfrom TB.Asmetforministhemostfrequentlyprescribedoral anti-diabeticinclinicalpractice,andsinceitsmechanismofaction, includingAMPKactivation,iswellknown,acomprehensive preventivestrategyofTBinDMshouldmandatetheuseof metformininalldiabeticsunlesscontraindicated.

Materials

and

methods

Thiscase–controlstudywasconductedinatertiarycare hos-pitalinSouth-India(KasturbaHospital (KH),Manipal)fora periodofeightmonths(August2015toMarch2016).Dataof patientsadmittedduringJan2011toDec2015wereobtained retrospectivelyfromtheMedicalRecordsDepartmentofthe hospital.SubjectswereidentifiedbasedonICD-10codingfor diseaseclassification(Diabeteswithoutcomplications:E11.9; tuberculosis:A15–A19).Studysubjectsweredividedintostudy group(SG:152)andcontrolgroup(CG:299).SGconsistedof dia-beticsdiagnosedwithTBandCGhaddiabeticswithoutTB.The ratiobetweencaseandcontrolwaskeptas1:2.Theinclusion criteriawasage≥40years.Patient’santi-diabeticmedications (metforminorotheranti-diabeticsoritscombinations)usage statuswerenoted.

Weusedcomputerized records foridentificationofcase andcontrols,assessmentofcomorbidities,andascertainment ofoutcome.Controldatawerecollectedfromdischarge sum-maryandidentifiednewlydetecteddiabetespatientswithno historyofTB,meetinginclusioncriteria.Patientsdiagnosed withDMbefore2011,below40years,withtuberculosiswere excludedfromcontrolgroup.Bothcaseandcontroldatawere fromthesamehospital,withsimilarexposurestatusandat riskofdevelopingsimilaroutcome.

TheCRFcaptureddemographicdata(age,gender,weight, height,BMI,occupation,andsocialhabits)andclinicaldetails (chiefcomplaintsonadmission,pastmedicalandmedication

history,casecategory,comorbidcondition,diagnosis,allergy status,laboratoryparameters,treatment,prognosis,discharge medication).Data were collectedforpopulationexposed to metforminandnon-metformin,i.e.otheroralhypoglycemic agents,OHA’s(sulfonylureas,alphaglycosidaseinhibitors, thi-azolidinedione,meglitinidesorinsulin)orcombinations.

Samplesize

ClinicalsignificanceintheincidenceratesbetweenSGandCG wasfixedat5%with80%powerand5%levelofsignificance. AstheratioofSG:CGwasfixedat1:2,theminimumnumberof subjectsrequiredinSGandCGweredeterminedtobe150and 300,respectively.Therefore,atotalsamplesizeof450subjects wereincludedinthestudy.

Statisticalanalysis

Numberand proportion ofpatientswith metformininthe TBcasegroupisthemainoutcomefortheanalysis.Results werereportedasrates&percentagesforcategoricalvariables, andmean&standarddeviationforcontinuousvariables.For univariateanalysis,Chi-square wasused. For the interven-tionmeasures,theabsoluteriskreductionsandthenumber neededtotreattopreventTBinonepersonwascalculated.

p-Value<0.05wastakenasstatisticallysignificant.

Ethicalclearance

Ethical clearance for study was obtained from Institu-tionalEthics CommitteeofKasturbaHospital, Manipal(IEC 430/2015).

Results

Studypopulation

We identified a total of 451 cases (Control, CG: 299 and Case,SG:152)whichincluded299controls,128diabeticsnot onmetforminand171 diabeticsonmetformin.Amongthe 152cases,111werenotonmetforminandremaining38were onmetformin.Generalcharacteristicsofstudypopulationare summarizedinTable1.

Amongthe299CG,194(64.9%)weremalesand105(35.1%) werefemales.InSG,120(79.5%)weremalesandremaining of24 (15.9%)were females.Themean (SD)ageofboth CG andSGwere55.54±11.82and52.80±11.75,respectively.We found that in both SG and CG, poor glycemic control (i.e. HbA1c>8.0)wasseenin51.7%and31.4%ofpatients, respec-tively.Similarly,FBS>100mg/dlwasseenin87.4%ofSGand 57.9%ofCG[Table2].Thirty-eight(25.5%)peopleintheSGand 171(57.1%)intheCGwereusingmetformin.Moreover,a sig-nificantproportionwerenotprescribedmetformininbothSG (n=111;74.5%)andCG(n=128;42.8%)[Table3].

Useofmetforminatanytimewassignificantlyassociated withreducedriskofTB.Oddsratio<1showsthatmetformin isprotectiveagainstTBbyafactorof3.9.Wedidnotfindany dosedependentprotectioninmetforminusers.Nodifference wasfoundbetweenthoseon1000mgmetformin,(27.3%)and

Table1–Generalcharacteristicsofstudypopulation.

Parameters Cases(N=152) Controls(N=299)

Ageinyears (mean±S.D.) 52.8±11.7 55.5±11.8 Gender(%) Male 124(82) 194(65) Female 27(18) 105(35) Durationof hospitalization (days) [median(range)] 7.0(5.0,10.0) 6.0(4.0,8.0) Numberof hospitalization [median(range)] 1.0(1.0,2.0) 1.0(1.0,2.0) BMI(mean±SD) (kg/m2₎ 21.2±3.7 25.8±15.7

Symptomsonadmission[No(%)]

Cough 100(66.2) 38(12.5) Fever 81(53.6) 29(9.7) Weightloss 17(11.3) 6.0(2.0) Breathlessness 15(9.9) 15.0(5.0) Fatigue 17(11.3) 11.0(3.7) HbA1c(%) [median±IQR] 9.3(7.5,11.6) 7.9(6.8,10.7) FBS(mg/dl) [median±IQR] 178(124,243) 163(125,234)

Table2–Glycemicstatusinthestudygroups.

Variable Cases[No(%)] Controls[No(%)]

HbA1c(%) <7.0 19.0(12.2) 60.0(20.1) 7.0–8.0 10.0(6.60) 50.0(16.7) >8.0 78(51.7) 94(31.4) FBS(mg/dl) <70 6.0(4.0) 4.0(1.3) 70–100 15(9.9) 14(4.7) >100 111(87.4) 173(57.9) Urinesugar 1+ 12(7.9) 12(4.0) 2+ 13(8.6) 25(8.5) 3+ 30(19.9) 73(24.4)

on500mg(25.7%)fordevelopmentofTB.Doseofmetformin doesnotseemtoaffecttheprotectiveoutcomeofmetformin againstTBinfection(OR=0.92;Chi2_{=0.05;p=0.82).}

Accordingtoourstudyresults,HbA1cvaluelessthan7was foundtobeprotectiveagainstTBoccurrence(OR<1),showing thatpoorglycemiccontrolisassociatedwithincreasedriskof TBinfections[Table4].

Discussion

MalesoutnumberedfemalesinbothCGandSGby64.0%and 29.8%,respectively.Asimilartrendinmaledominancewas observedinotherstudiesbyDobleretal.,12_andFezaetal.13

TBincidencewashighestindiabeticsaged51–60years(n=47) inthisstudy.AccordingtoDobleretal.,12_{themajorityofTB}

in DM patients was observedin age group of55–74years. Thereasoncould bebecausemetabolicdisorders caneven atayoungerageinIndianscomparedtoWesterners.14,15_Our

Table3–Metforminusagepatternsinthestudygroups.

Exposurestatus Studyoutcome Total Statisticaltests

Case[No(%)] Control[No(%)]

Present(metformin) 38(18.2) 171(81.8) 209(100) Chi2_=40.12;

p=0.00 OR=0.256(0.16, 0.40)

Absent(non-metformin) 111(46.4) 128(53.6) 239(100)

Total 149(33.3) 299(66.7) 448(100)

Table4–RiskofTBoccurrenceandglycemiccontrol.

HbA1cstatus Studyoutcome Total Statisticaltests

CaseNo.(%) ControlNo.(%)

<7 19(24.1) 60(75.9) 79(100) Chi2_=5.03; p=0.025 OR=0.52(0.29, 0.93) >7 88(37.9) 144(62.1) 232(100) Total 107(34.4) 204(65.6) 311(100)

inclusioncriteria,hadsubjectsmorethan40years.TB inci-dencewasnotage-dependent;51–60years(30.9%)and41–50 years(26.3%).However,theincidenceofTBwaslowerinelders 61–70years(n=24,15.8%)andabove70years(n=12,7.9%).

Wefoundthatsmokingandlowincomeweresignificantly associatedwithtreatmentfailureofTB,whichisinagreement withanotherstudybyTachfouti etal.16 _{Lowsocioeconomic}

statusindicatorssuchasovercrowding,illiteracy,lowwages andunemploymentwere associatedwithincreasedriskfor TBaswellaspoormedicationadherence.17

WeobservedthatthemajorityofTBpatientsdidnothave anysignificantfamily history(84.8%).However,11.9%cases hadfamilyhistoryofdiabetesbutverylowincidence(2.6%) offamily history ofTB.Due toincompletemedicalrecords andpoorfamily historydocumentationbyphysicians, fam-ilyhistorydataweremissinginmostofourstudypopulation. MostfrequentlyobservedsymptomsinSGwerecough(66.2%), fever(53.6%),weightloss(11.3%),fatigue(11.3%)and breath-lessness (9.9%). The majority of SG had a poor control of glycemiclevels,withHbA1c>8%(51.7%)andFBS>100mg/dl (87.4%).AsystematicreviewbyChristieetal.in2010 demon-stratedhigherincidenceofhyperglycemiainTB,rangingfrom 1.9to35%,possiblybecause ofchronicinflammation, sub-optimumtherapy adherence,drug–drug interaction,access and affordability of health services and side effects like vomiting.18

Inourstudy,distributionofaverageHbA1c values(<7.0, 7.0–8.0and>8.0)were12.2%,6.6%and51.7%,respectively.We observedthatHbA1c<7groupwashavingminimalriskforTB. ThediabeticswithHbA1c>7wereattwice,higherriskforTB. ComparingwithLeegaardetal.study,averageHbA1cinthe similargroups(<7.0,7.0–8.0and>8.0)were1.8%,0.7%and1.6% respectively,whichwasfoundtobemuchlowercomparedto ourstudy.However,94%ofthesubjectswerenon-diabetics intheirstudy.19_{Similarresultsasourstudywasreportedby}

Leungetal.,whichstatesthatpatientswithHbA1cvalue>7 areattwofoldhighertheriskofactiveTB.20

Several mechanismshave been proposedto explainthe highriskofTBinDM.DiabeticsarevulnerabletoTBdueto impaired monocyte chemotaxis, reduced interferon (IFN ␥) and activation ofalveolarmacrophages, diminishedtype1 cytokineexpression,andinnateimmunity.20

ThegrowthandinfectionofM.tbincellsdependonthe innateandadaptiveimmuneresponsesofthehost.Thehost cellphagolysesbacteriabythegenerationofreactivenitrogen and oxygen species. This autophagy pathway is regulated by mTOR complex-1, serine/threonine kinase, and AMPK. Singhaletal.reportedthatmetformin-inducedactivationof AMPKinhibitsmycobacterialgrowthinmacrophages.Hence, it wassuspectedtohavepotentialeffectonanti-tubercular regimen in diabetics due to its role in maintaining the phagosomalpathwayandpromotingantibacterialaction.11

Ourstudyhasdemonstratedthatthepatientswhowere on metformin had a protective effect against tuberculosis 3.9 timescompared toother hypoglycemictreatment regi-mens.But,wefoundboth500mg(25.7%)and1000mg(27.3%) ofmetformindoseshavenodifferenceinprotectiveaction. Hence, the study exhibits metformin can exert protective action against TB, irrespective of different doses of the metformin.Itwasfoundthatmetforminwaspartofthe pre-scriptioninjust25.3%ofSGand57.1%oftheCG.Metformin shouldbeincludedinthetherapyforalltype2DMpatients, iftoleratedandnotcontraindicated,asitistheonlyoral anti-hyperglycemicmedicationproventoreducetheriskoftotal mortality,accordingtotheUnitedKingdomProspective Dia-betesStudy(UKPDS).

Conclusion

The study concludes that metformin has protective effect indiabeticpatientsagainsttuberculosisinfection.Acid-fast bacilli weredominantly foundtobepositiveamonghigher HbA1c (>8%). Poor glycemic control was associated with

increased risk of TB infections. This protective effect of metforminagainsttuberculosisisnotdosedependent.Due topoormedicationhistorydocumentation,wewerenotable togatherdurationofmetforminuse.Hence,wewerenotable toassessmetforminusagedurationrelationshipwithits pro-tectiveaction.However,wefoundapositivecorrelationwith singleand/orshort-termexposureofmetformincanproduce longtermimmunityagainstTBinfection.

Ethical

approval

InstitutionalEthicalClearanceobtainedfromKasturba Hospi-tal(KH),Manipal,India(IEC430/2015).

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

Acknowledgements

WeexpressourgratitudetoManipalCollegeofPharmaceutical Sciencesand KasturbaMedicalCollege,ManipalUniversity, Manipalforthesupport.

r

e

f

e

r

e

n

c

e

s

1. MaxmenA.AheadofWHOmeeting,expertsclashover tuberculosistargets.NatMed.2013;19:115.

2. WorldHealthOrganization.Globaltuberculosisreport2015. 20theditionGeneva,Switzerland:WHO;2015,

http://www.who.int/tb/publications/globalreport/en/.

3. ZumlaA,GeorgeA,SharmaV,HerbertRH,BaronessMasham ofIlton,OxleyA,OliverM.TheWHO2014globaltuberculosis report–furthertogo.LancetGlobHealth.2015;3:e10–2.

4. LönnrothK,RoglicG,HarriesAD.Improvingtuberculosis preventionandcarethroughaddressingtheglobaldiabetes epidemic:fromevidencetopolicyandpractice.Lancet DiabetesEndocrinol.2014;2:730–9.

5. StevensonCR,ForouhiNG,RoglicG,etal.Diabetesand tuberculosis:theimpactofthediabetesepidemicon tuberculosisincidence.BMCPublicHealth.2007;7:234.

6. SyedSuleimanSA,IshaqAweisDM,MohamedAJ, RazakmuttalifA,MoussaMA.Roleofdiabetesinthe

prognosisandtherapeuticoutcomeoftuberculosis.IntJ Endocrinol.2012;2012:645362.

7.BalakrishnanS,VijayanS,NairS,etal.Highdiabetes prevalenceamongtuberculosiscasesinKerala,India.PLoS One.2012;7:e46502.

8.BalakrishnanS,PremaJ,SunilKumarM,NairS,DawanPK. Diabetesmellitusincreasesriskoffailingtreatmentindrug susceptibleTBpatients.IntJTubercLungDis.2011;3:S348.

9.PunjabiCD,PerloffSR,ZuckermanJM.Preventing transmissionofMycobacteriumtuberculosisinhealthcare settings.InfectDisClinNorthAm.2016Sep19[Epubaheadof print].

10.ZhouG,MyersR,LiY,etal.RoleofAMP-activatedprotein kinaseinmechanismofmetforminaction.JClinInvest. 2001;108:1167–74.

11.SinghalA,JieL,KumarP,etal.Metforminasadjunct antituberculosistherapy.SciTranslMed.2014;6:263ra159.

12.DoblerCC,FlackJR,MarksGB.Riskoftuberculosisamong peoplewithdiabetesmellitus:anAustraliannationwide cohortstudy.BMJOpen.2012;2:e000666.

13.Bacako ˘gluF,Bas¸o ˘gluOK,CokG,SayinerA,Ates¸M.Pulmonary tuberculosisinpatientswithdiabetesmellitus.Respiration. 2001;68:595–600.

14.SonalSekharM,UnnikrishnanMK.South-Asianpopulation hasahigherlikelihoodfordiabetesriskforstatinsregardless ofpotency.MedHypotheses.2015;84:283–4;

RamachandranA1,SnehalathaC,ShettyAS,NandithaA. TrendsinprevalenceofdiabetesinAsiancountries.WorldJ Diabetes.2012;3:110–7.

15.TachfoutiN,NejjariC,BenjellounMC,etal.Association betweensmokingstatus,otherfactorsandtuberculosis treatmentfailureinMorocco.IntJTubercLungDis. 2011;15:838–43.

16.CantwellMF,McKennaMT,McCrayE,OnoratoIM.

Tuberculosisandrace/ethnicityintheUnitedStates:impact ofsocioeconomicstatus.AmJRespirCritCareMed.1998;157 4Pt1:1016–20.

17.JeonCY,HarriesAD,BakerMA,etal.Bi-directionalscreening fortuberculosisanddiabetes:asystematicreview.TropMed IntHealth.2010;15:1300–14.

18.LeegaardA,RiisA,KornumJB,etal.Diabetes,glycemic control,andriskoftuberculosis,apopulation-based case–controlstudy.DiabetesCare.2011;34:2530–5.

19.LeungCC,LamTH,ChanWM,etal.Diabeticcontrolandrisk oftuberculosis:acohortstudy.AmJEpidemiol.

2008;167:1486–94.

20.DooleyKE,TangT,GolubJE,DormanSE,CroninW.Impactof diabetesmellitusontreatmentoutcomesofpatientswith activetuberculosis.AmJTropMedHyg.2009;80:634–9.