Accuracy of heparin binding protein: as a new marker in prediction of acute bacterial meningitis

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Clinical

Microbiology

Accuracy

of

heparin

binding

protein:

as

a

new

marker

in

prediction

of

acute

bacterial

meningitis

Mona

Kandil

a

_,

_Gihane

_Khalil

a

_,

_Eman

_El-Attar

a,∗

_,

_Gihan

_Shehata

b

_,

_Salwa

_Hassan

c

a_Alexandria_University,_Medical_Research_Institute,_Chemical_Pathology_Department,_Alexandria,_Egypt

b_Alexandria_University,_Medical_Research_Institute,_Biomedical_Informatics_and_Medical_Statistics_Department,_Alexandria,_Egypt c_Ministry_of_Health,_Ministry_of_Health_Specialized_Hospital,_Alexandria,_Egypt

a

r

t

i

c

l

e

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n

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o

Articlehistory:

Received16November2017 Accepted29May2018

Availableonline17August2018 AssociateEditor:AfonsoBarth

Keywords:

Communityacquiredmeningitis Acutebacterialmeningitis Heparinbindingprotein CSFbiomarker

Serumbiomarker

a

b

s

t

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Background:Cerebrospinalfluidbacterialcultureisthegold-standardforconfirmationof acutebacterialmeningitis,butmanycasesarenotcultureconfirmed.Antibioticsreduce thechanceofamicrobiologicaldiagnosis.ObjectivetoevaluateefficacyofHeparin-binding proteinindiagnosisofbacterialmeningitis.

Patients:30patientsdiagnosedwithacutebacterialmeningitis,30viralmeningitis,and30 subjectswithnormalCSFﬁndings.

Design:Diagnosis was basedon history, clinicalcriteria,CSFexamination, latex agglu-tination&culture,and sensitivitiesandresponsetotherapy. HBPwasmeasuredusing enzyme-linkedimmunosorbenttechniqueinbothserum&CSF.

Results:CerebrospinalfluidHBPlevelsaveraged0.82±0.3ng/mLincontrols,3.3±1.7ng/mL in viral and 174.8±46.7ng/mL in bacterial meningitis. Mean serum level was 0.84±0.3ng/mLinthecontrols,3.7±1.9ng/mLinviral,and192.2±56.6ng/mLinbacterial meningitis.BothHBPlevelsweresignificantlyhigherinpatientswithbacterialmeningitis. Cut-offsof56.7ng/mland45.3ng/mlincerebrospinalfluid&serumshowed100%overall accuracy.Eveninpatientswhoreceivedpriorantibiotics,remainedelevated.

Conclusion: SerumHeparin-bindingproteinservesasa non-invasivepotentialmarkerof acutebacterialmeningitiseveninpartiallytreatedcases.

Introduction

Meningitis isthe mostcommon infectious centralnervous systemsyndrome.Acutebacterialmeningitis(ABM)isa life-threateningneurologicalemergency.Itisoneofthe top10 causesofinfection-relateddeathworldwide.Ifleftuntreated,

∗ _{Corresponding}_author_at:₄₇_Sultan_Hussein_St.,_Alexandria,_Egypt.

E-mails:[email protected],[email protected](E.El-Attar).

itsmortalitycouldapproach100%.1_Even_with_current

antibi-oticsandadvancedintensivecare,themortalityrateofthe disease is approximately 10%; and 30–50% ofits survivors livewith permanentneurologicalsequel followinghospital discharge. Theclinical distinction between viral and acute bacterial meningitis is difﬁcult in the acute phase of ill-ness because the symptomsare oftensimilar. Community

https://doi.org/10.1016/j.bjm.2018.05.007

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acquiredmeningitisreferstobacterialmeningitiscausedby

Haemophilusinﬂuenzae(mostlytypeb), Streptococcus pneumo-niaorNeisseriameningitidis.These comprise70–90%ofABM cases.1,2

According to WHO guidelines, CSF (cerebrospinal ﬂuid) analysis isessential to establish the diagnosis, distinguish bacterialfromviralmeningitis,and toidentifythe etiologi-calagent.3 _Bacterial _culture_is_the_{gold-standard} _technique

forABM confirmation,due to its high specificity for iden-tification of the etiologic agent (WHO, 2011). However, approximately 50% of suspected cases are not culture-confirmed. Thus, clinical criteria, culture, Gram staining, and bacterial antigen testing of CSF as well as the clas-sical markers in CSF: CSF lactate, protein, glucose, white blood cell (WBC), and neutrophil count are used. Unfortu-nately,noisolatedlaboratorytesthasdistinguishedbacterial meningitisfrom asepticmeningitis with100%sensitivity& specificity; and the most accurate combination of clinical features to raise or lower suspicion of meningitis is still unclear.4,5

Potentialapplicationsofbiomarkersininfectiousdiseases includedistinguishingbacterialfromnonbacterialinfection, monitoring response to therapy, and predicting outcomes. Heparin-binding protein (HBP), also known as Azurocidin and Cationic Antimicrobial Protein (CAP37), is a positively charged37kDglycoproteinreleasedfromthesecretory vesi-cles and azurophilic granules of activated neutrophils in severe sepsis. Structurally, it belongs to a hematopoietic serine protease superfamily with antimicrobial function. It forms a part of the innate defenses of human neu-trophils.HBPiseasilyandrapidlymobilizedfrommigrating neutrophils.6

Theaim of this study is to evaluatethe role of serum and CSF heparin binding protein in diagnosis of bacterial meningitis,and itsefﬁcacy indifferentiatingbacterialfrom non-bacterialmeningitis;inordertoverifythepossibilityof usingtheHBPininitialevaluationofABM.

Methods

Studysetting:Thepresentstudy wasconductedinthe Min-istryofHealth Specializedhospital, Alexandria,Egypt.Itis thelargesthospitalofitskindinAlexandria;atertiarycare facilityandacenterofexpertiseincareandmanagementof feverpatients.ItservesthepopulationofAlexandriacityand nearbygovernorateswithaconsiderablecaseloadthat war-rantstheaccumulationofasufﬁcientnumberofcasesduring areasonableperiodoftime.

Studydesign:Cross-sectionalstudy.

Study population: the study population encompassed 90 patientswhowereadmittedtotheFeverHospitalin Alexan-dria, Egypt, and were clinically suspected to have acute meningitis end of2016 & early 2017. Diagnosiswas based onhistory,clinicalcriteria,andCSFexaminationcriteria.3,7–10

Accordingtodiagnosis andtherapeuticoutcome,thestudy populationwasclassiﬁedintothreegroups:GroupIincluded 30patientsdiagnosedwithABM,GroupII30 patientswere diagnosedwithnon-bacterial(mostlyviral)meningitis,and,

ﬁnally,GroupIIIincluded30subjectswithnormalCSF exam-inationﬁndings(controlgroup).

Inclusioncriteria:Patientswithmeningitisadmittedtothe MinistryofHealthSpecializedHospital.

Exclusion criteria: patients with tuberculous meningitis, brain space occupyinglesions, HIVinfection (orwho were onimmunosuppressivetherapy),chronicbacterial meningi-tis,post-surgicalmeningitis,andthosewithahistoryofhead trauma,wereexcludedfromthestudy.

Sample sizecalculation: aminimumsamplesizeof29for eachgroupwascalculatedtoachieve80%power;andtodetect differenceof0.219betweentheareaunderthecurveofthenull hypothesis(0.78)andthealternativehypothesisof(0.999)with asigniﬁcancelevelof0.05

Tools of data collection: the study follows the principles of the Declaration of Helsinki.Consequently, aftergaining approvalfrom:theEthicalcommittee,MedicalResearch Insti-tute, Alexandria University, Ministry of Health Specialized Hospital, andMinistryofHealth;signedinformedconsents were obtainedfromallpatientsortheirguardians, profess-ingtheiracceptancetoparticipateinthestudyandhavethe resultspublished.

Three tools were used to obtain relevant information: Interviewingquestionnaire,clinicalexamination,and inves-tigations.

- Interviewing questionnaire: an interview schedule was designedto collect relevantinformation from all eligible patientsortheirguardiansenrolledinthisstudy.The sched-ule included the followingitems: personal, past medical historyandpresentcomplaint.

- Clinicalexamination: complete clinical examinationof the studysubjectswasperformed.

- Investigations:alaboratoryworkupwasdone;CSFandblood samples were drawn simultaneously under aseptic pre-cautions. CSF was collected by the attending physician in sterile tubes for chemical, microbiological and cyto-logical examination. Biochemical examination included glucose, protein and lactate, which were determined in CSF supernatantsamples aftercentrifugationat 2000×g

for 5min. A wet preparation of CSF was used for total WBCs count. Gram stain for detection of bacteria and differential WBC count on CSF sediment was done. For CSFbacterialculture,CSFwas centrifugedat1000×gfor 10–15min to sediment bacteria, cultured on blood agar and chocolate agar plates,incubated for18–24h at37◦C inacandle-jar,andexaminedafter18–24h.Agglutination testingforH.inﬂuenzae, N.meningitidis,andS.pneumoniae

using the CSF supernatant for the detection of solu-ble bacterial antigens(capsular polysaccharide)was also done.

For serum heparinbindingprotein, wholevenous blood was drawn from each subject. Blood was allowed to clot for 20minatroom temperature, centrifuged andaliquoted at −20◦_C _for _the _{determination} _of _the _{concentrations} _of

serum HBP, using Enzyme Linked Immunosorbant Tech-nique (Glory science Co., Ltd, Hangzhou, China). Serum & CSF HBP were measured according to the manufacturer’s instructions.11

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Table1–CharacteristicsofthestudysampleandHBPlevelsinCSFandserum.

Characteristics Bacterialgroup Viralgroup Controlgroup Total

n=30 n=30 n=30 n=90 Gender Male 19(63.3%) 18(60)% 12(40%) 49(54.4%) Female 11(30.6%) 12(40)% 18(60)% 41(45.6%) Ageinyears Mean±SD 24.7±14.7 24.7±14.8 24.9±14.3 24.9±14.5 (Minimum–maximum) (1.5–50) (1.0–49) (1.5–50) (1.0–50) Pre-admissionantibiotic 25(83%) 27(90%) 24(80%) 76(84.4%) CSFHBPlevelinng/ml Mean±SD 174.8±46.7 3.3±1.7 0.82±0.3 (Minimum–maximum) 56.7–295 1.30–7.5 0.31–1.8 SerumHBPlevelsinng/ml Mean±SD 192.2±56.6 3.7±1.9 0.84±0.3 (Minimum–maximum) 45.3–289 1.1–7.6 0.4–1.51

Statisticalanalysis:was performedusingIBMSPSS soft-warepackageversion20.0.

- The qualitativevariables were summarizedby frequency andpercentage.Chisquaretestwasusedtotestfor asso-ciation between the type of meningitis and the other qualitativevariables.MonteCarlotestwasusedwhenmore than20%oftotalcellshadexpectedcellcounts<5. - Thedistributionsofquantitativevariablesweretestedfor

normalityusingKolmogorov–Smirnovtestandrevealed nor-maldatadistribution;andparametrictestswereapplied. - Thequantitativevariablesweresummarizedbythemean

and standard deviation. One-way ANOVA was used for Comparisonsofgroupdifferencesregardingthecontinuous variables.Correlationsbetweenquantitativevariableswere assessedusingPearsoncorrelationtechnique.

The Receiver Operating Characteristic (ROC) curve was usedtoevaluateaccuracyofHBPmarkerinpredictionof bac-terialmeningitis.Areaunderthecurvevaluesisreportedwith the95%confidenceinterval(CI).Allaccuracymarkerswere calculated:Sensitivities, specificities, positive and negative predictivevalues.Significanttestresultswerequotedas two-tailedprobabilities.Significanceoftheobtainedresultswas judgedatthe5%level(p≤0.05).

Results

CharacteristicsofthestudysampleandHBPlevelsinCSFand serumareillustratedinTable1.CSFHBP&serumHBPlevels werebothsigniﬁcantlyhigherinpatientswithacutebacterial meningitisthaninpatientswithviralmeningitisandcontrols. ThissuggeststhepotentialroleofbothCSF&serumHBPin distinguishingbetweenacutebacterialandviralmeningitis (p<0.01)(Fig.1).

Table2andFig.1showtheaccuracymeasures(atcutoff pointwithhighestsensitivityandspeciﬁcity)ofthe conven-tionalCSFparametersandHBPasanewmarker.Fordiagnosis ofbacterialmeningitis,theoverallaccuracyofCSFWBCsata cutoffof877.5cells/cmm,CSFneutrophilsatacutoffof59%, CSFproteinatacutoffof45.5mg/dl,CSFglucoseatacutoff

of39.5mg/dl,andthatofCSFlactateatacutoffof29.5mg/dL were:91.1%,99.7%,84.6%,82.5%,and92.7%respectively.

AcutoffpointofCSFHBPlevelat56.7ng/mlshowed100% sensitivityandspeciﬁcity;positiveandnegativepredictive val-uesof100%;andoverallaccuracyof100%.Atacutoffpointof 45.3ng/mlserumHBPalsoshowed100%sensitivityand speci-ﬁcity; positive and negativepredictive valuesof 100%; and overallaccuracyof100%.Areasunderthecurvewere1.0for bothCSFand serumHBP;whichwerehigherthanallother investigatedparameters(Fig.1).

Table3illustratesahighlysigniﬁcantpositivecorrelation betweenCSFHBP, serumCSFandotherCSFﬁndings;WBCs, neutrophils percent,protein,lactateand decreasedglucose levels.

Lastly,Fig.2showsahighlysigniﬁcantpositivecorrelation betweenCSFand serumHBPlevels (r=0.93,p=0.000)inthe threegroups(Fig.2).

Discussion

Adverse effects oflumbar puncture include headache and backache. Complications may also occur in limited cases such as cerebral herniation, intracranial subdural hemor-rhage,spinalepiduralhemorrhage,andcranialandsubdural hematomasfromdecreasedCSFpressure.Mostimportantly, thereisanumberofsituationswhereLPmaybe contraindi-cated incasesatthe age of60or older,or casessuffering from:coagulopathies,immunocompromisedstate,historyof centralnervoussystemdisease,seizureandlocalinfectionat the puncture siteinmasslesions,andventricular obstruc-tioncausingraisedintracranialpressureandbrainabscess.12

Hence,alessinvasivesample(asbloodserum),toaidoreven replaceLPforthediagnosisandfollowupofmeningitis,would beofagreatbeneﬁt;notonlytothepatientsbutalsoto physi-ciansandclinicallaboratories.

Inthisstudy,all30patientswithpositiveCSFﬁndingsin ABMgrouphadelevatedserumHBPlevels(192.2±56.6ng/mL). Consideringthesigniﬁcantmorbidityassociatedwithlumbar punctureandcontraindicationtoperformaCSFtapping,the positivecorrelationbetweenCSFandserumHBPlevelsmay furthersupportthepotentialuseofserumHBPasadiagnostic

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ROC Curve

1 - Specificity

Diagonal segments are produced by ties.

Sensitivity

Source of the Curve WBCs /mm3 Neutrophills % of total wbcs

CSF protein (mg/dl) CSF lactate (mg/dl) Heparin Binding Protein in CSF (ng/ml) Heparin Binding Protein in Serum (ng/ml) Reference Line 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0

Fig.1–Receiveroperatorcharacteristicscurveofcerebrospinalﬂuidtotalwhitebloodcells,%neutrophils,protein,lactate andserumHeparinbindingproteininpredictionofbacterialmeningitis.

Table2–AccuracymeasureswiththecutoffpointsofHBPandoldmarkersinpredictionofbacterialmeningitis. Biomarker Cutoff Sensitivity Speciﬁcity Overallaccuracy(areaunderthecurve95%C.I) pvalue

CSFWBCs 877.5cells/mm3 _63.3% _100% _91.1%_{(85.1–97.1%)} _0.000 CSFneutrophils% 59% 100% 97% 99.7%(99.1–100%) 0.000 CSFprotein 45.5mg/dl 83.3% 70% 84.6%(76.2–93%) 0.000 CSFGlucose 39.5mg/dl 50% 100% 82.5%(71.7–92.8) 0.000 CSFLactate 29.5mg/dl 90% 87% 92.7%(86.1–99.4%) 0.000 CSFHBP 56.7ng/ml 100% 100% 100% 0.000 SerumHBP 45.3ng/ml 100% 100% 100% 0.000

Table3–CorrelationbetweenCSFandSerumHBPlevelsandCSFtraditionalmarkers.

TraditionalCSFmarkers CSFHBP SerumHBP

CSFWBCscount/mm3 _r₌_0.349,_p₌_0.001 _r₌_0.295,_p₌_0.005

CSFneutrophils%oftotalCSFWBCs r=0.907,p=0.000 r=0.916,p=0.000

AbsoluteCSFneutrophilscount/mm3 _r₌_0.347,_p₌_0.001 _r₌_0.295,_p₌_0.005

CSFglucose(mg/dl) r=−0.583,p=0.000 r=−0.617,p=0.000

CSFProtein(mg/dl) r=0.574,p=0.000 r=0.589,p=0.000

CSFLactate(mg/dl) r=0.662,p=0.000 r=0.687,p=0.000

markerinsubstitutionoftraditionalCSFanalysis.Therefore, serumHBPmaybeusedinconﬁrmingorrulingoutthe diag-nosisofclinicallysuspectedbacterialmeningitis,especially incaseswherelumbarpunctureiscontraindicated.Also,the possibilityofreplacingfollowupLPwithserumHBPisworth furtherinvestigation.

Inmanyclinicalsettings,involvingpatientswithclinical suspicion ofbacterial meningitis, antibiotics are instituted beforelumbarpuncture;reducingthe chanceofa microbi-ological diagnosis. Eighty three percent of our patients in thebacterialgroupreceivedantibiotics48–72hbeforelumbar puncture. However, these patients still maintained signiﬁ-cantlyelevatedCSFandserumHBPlevels.

Inthis study,meningitiswasconﬁrmedbybacterial cul-ture,Gramstainingand/oragglutinationtesting,onlyin16.7%

ofpatients.However,theremaining83.3%ofpatientsinthe bacterialgroupwerediagnosedasbacterialaccordingto: pos-itivetraditionalCSFlaboratoryfindings,clinicalfindings,and response to treatment. The low detection rates ofculture, Gramstainingandagglutinationcomparedcouldbeexplained by low concentration of pathogens or empirical antibiotic treatmentpriortosamplecollectionwhichreducesthe diag-nosticsensitivityofthesetests. Ithasalsobeenshownfor patientsofbacterialgroupthatCSFlevelsofprotein(in16.7% ofpatients),glucose(in50%ofpatients),andlactate(in10% ofpatients)couldnotdifferentiatebetweenbacterialandviral meningitis;denotingtheneedofadditionalsensitiveand spe-cificmarkers.

As a granule-associated protein, HBP is rapidly mobi-lized frommigratingpolymorphonuclear leukocytes.Itacts

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300.00

( r = 0.928,P = 0.000)

Hepar

in Binding Protein in CSF (ng/ml)

Heparin Binding Protein in Serum (ng/ml)

250.00 200.00 150.00 100.00 50.00 .00 .00 50.00 100.00 150.00 200.00 250.00 300.00

Fig.2–CorrelationbetweencerebrospinalﬂuidandserumHBPlevels.

as a chemoattractant, an activator of monocytes and macrophages, and induces vascular leakage and edema formation.ThereleaseofHBPistriggeredbyligationof neu-trophilic ␤2-integrins; a process that may be initiated by bacteria.Theoveralloutcomeispowerfulvascularleakage.13

WhentheseeffectsareappliedtothecaseofABM, neutrophil-derivedHBPproductioncouldresultfromtheinﬂammatory responsetobacterialinfectionandcouldhaveamajorrolein theresultantbraininjuryandbrainedemainABM.

HBPwas proposedasamarkerofbacterialinfection for earlydetectionofpatientsinthe emergencydepartmentat riskofdevelopingseveresepsisandsepticshock.It demon-stratedsigniﬁcantpredictivevaluesofelevatedlevelsofHBP inbloodofpatientswithseveresepsisand septicshock as comparedtoHBPlevelsinpatientswithnoninfectiouscritical illness,andascomparedtoothermarkers.ElevatedHBPlevels (>30ng/ml)werefoundin80%ofthepatientswhileelevated procalcitonin levels (>0.5ng/ml)were detectedin 59%, ten andahalfhours(median)beforedevelopingseveresepsis.14

Linderet al.(2012)15_found_{signiﬁcantly}_higher_plasma_HBP

inpatientswithseveresepsisorsepticshock,ascompared to patients with a non-septicillness in the intensive care unit.HBPwasassociatedwithseverityofdisease,andan ele-vated HBP atadmission was associatedwith an increased risk of death. They recommended repeated HBP measure-ment in the ICU may help monitor treatment and predict outcome in patients with severe infections. Holub, Beran (2012),16_and_Bentzer₍₂₀₁₆₎17_reported_similar_ﬁndings._Other

studies present the role of HBP as a serum biomarker of bacterialinfections.13,18–20_Linder₍₂₀₁₅₎21 _suggested_HBP_as

thebestpredictorandanearlyindicatorofinfection-related organdysfunction;andastrongpredictorofdisease progres-sionto severe sepsis within72h inpatients presenting at theemergencydepartment.Finally,in2017Fisher& Linder acknowledgethatHBPhasamajorroleinthepathophysiology

ofseverebacterialinfectionsand,thus,representsapotential diagnosticmarkerandatargetforthetreatment.22_Another

study for them laterthat year statesthat elevated plasma HBPisassociatedwithdevelopmentofsepsis-inducedacute kidneyinjury.23

Presumably, HBP was scarcely investigated in CSF of patients. Linder et al. (2011)11 _analyzed _CSF _samples _for

the concentrations of HBP, lactate, protein, glucose, neu-trophils, and mononuclear cells. HBP levels in CSF were significantlyhigher (p<0.01) inpatientswith ABM(median 376ng/mL, range 12–858ng/mL) than in patientswith viral meningitis(median4.7ng/mL,range3.0–41ng/mL),orcontrol patientswithnormalCSFcellcount(median3.5ng/mL,range 2.4–8.7ng/mL).TheysuggestedaCSFHBPcutoffconcentration exceeding20ng/mLtodiagnoseABM;withsensitivity100%, specificity99.2%,andpositiveandnegativepredictivevalues of96.2%and100%.TheareaundertheROCcurvefor heparin-bindingproteinwas0.994,whichwashigherthanthatforthe other investigatedparameters. Linderetal. concludedthat elevatedCSFlevelsofHBPcoulddistinguishbetweenpatients withacutebacterialmeningitisandpatientswithother cen-tralnervoussysteminfections.Wenotetherelativelysmall numberofpatientsincludedintheirstudy(41bacterial menin-gitispatientsand10viralmeningitispatients).Theresultsin thisstudyconcurwithandconfirmtheseresults.Moreover, thepresentstudytookastepfurtherasitisthefirststudyto investigateserumHBPinmeningitisandtocorrelatebetween CSFandserumHBP. Thestudyalsolocatesaweakpositive correlationbetweenCSFHBPandCSFpolymorphonuclearcell counts.ThiswasalsonotedbyLinderetal.;and they sug-gestedthatHBPlevelprobablyreflectsthenumberofactivated neutrophilsratherthantheabsoluteneutrophilcount.

PCRtestingismoresensitivethanCSFculture,particularly inpatientswhoreceivedpreviousantimicrobials.CSF bacte-rial culturerequiresthatlaboratoriesreceivelivingbacteria

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whichisquietrestrictingtakingintoconsiderationthefragility ofthethreecausativebacteriaofcommunityacquired menin-gitis.However,PCRcannotberoutinelydoneinthediagnosis ofevery caseof bacterial meningitis;it is more expensive andnotavailableinresourcelimitedsettings,asisthecase indevelopingcountries. ThereforePCRisnotusually avail-ableforroutinecasemanagement;itcanberetrospectively usedinsurveillancepurposesforadaptingthemost appropri-atepreventivestrategy.24_In_patients_with_suspected_bacterial

meningitis,empiricaltherapyshouldnotbedelayedformore thanonehourwhileawaitingdiagnostictesting.Inthe mean-time,HBPtestingcanofferarapid,affordabletooltodetect patientswithearlybacterialmeningitisorpatientswhohave beenpartiallytreated.

Giventhe lackofspecificityofclinical findings,the key tothediagnosis ofmeningitisisthe evaluationofCSF. Ini-tiationofantimicrobialsbefore lumbarpuncture decreases theyieldofCSFculture;Gramstaining;CSFpleocytosis;the likelihoodofalowCSFglucoselevel;andthedegreeof ele-vationofCSFproteinandofCSFlactate.Moreover,patients with early bacterial meningitis might not have the classi-cal positive CSF findings of bacterial meningitis. However, Heparin-bindingproteinisapromisingnewbiomarkerthat might assist with early identification of bacterial menin-gitis as well as partially treated bacterial meningitis. It is recommend to have further studies on larger scales. CSF HBP level ≥56.7ng/mL; and serum HBP level ≥45.3ng/mL should prompt empirical therapy for bacterial meningitis while awaiting results of CSF culture or even molecular assays.

CSF and serum HBP were both signiﬁcantly higher in patientswithacutebacterialmeningitisthaninpatientswith viralmeningitisandcontrols;despitetheintakeofantibiotics. CSFHBPlevelat56.7ng/ml,andserumHBPlevelat45.3ng/ml showed100%sensitivityandspeciﬁcity,andpositiveand neg-ativepredictivevaluesof100%,andoverallaccuracyof100% forthisparameter.

Ourstudyshedslightontheexcellentdiagnostic perfor-manceofHBPinthediagnosisandpossiblyfollowupofacute bacterialmeningitis.SinceCSFHBPwashigherthanserum HBPinABM patients,it issafetoassume thatHBPis pro-ducedlocallyintheCSFandisnotcomingfromasystemic source.ThecorrelationofserumandCSFlevels&otherCSF parameterssuggeststhatserumlevelsofHBPcanbeusedas anon-invasivetestofABM.However,duetothelackof speci-ficity,serumHBPcannotconfidentlyreplacethefirstCSFtap. HighlevelsofserumHBPwhenusedalonecouldalsoindicate systemicbacterialinfection&sepsis.Thustheuseofserum

HBP(alonewithoutCSFHBP)indiagnosisofABMhastobe incontextwithclinicalﬁndings.WesuggestthatserialHBP measurementscouldbefurtherstudiedasareplacementfor thesecondCSFtapinthefollowupofABM.

MeasuringHBPinCSFfrompatientswithsuspected menin-gitiscouldimprovethediagnosticaccuracyindifferentiating betweenbacterialandviralmeningitis,therebyallowingthe cliniciantostartadequatetreatmentearlier;especiallyin sit-uationsorplaceswhenthetimeandresourcesarelimited. Resultsofthisstudypointoutthepossibilityofconsidering

serum HBPas a diagnostic markerin substitution of tradi-tionalCSFanalysisinconﬁrmingorrulingoutthediagnosisof

communityacquiredABM;especiallywithabsoluteand rela-tivecontraindicatedlumbarpuncture.

HBPcouldbeapromisingbiomarkerthatmightassistwith earlyidentiﬁcationofbacterialmeningitisaswellaspartially treated bacterial meningitis.HBPcould be introduced asa routinetestforpatientswithABM;especiallywhenkitsfor its determinationareavailableonacommercialautomated basisandnotonlyforresearchstudies.Theseresultswarrant evaluationindifferentpopulationsandlargerscale.Further research forserial measurementsofHBPplasma levelsfor closemonitoringofcriticallyillmeningitispatients,instead ofrepeatedlumbarpuncturewhichiscurrentlyusedinfollow upofacutebacterialmeningitiscases,isrecommended.

Disclosures

• Thisworkwasself-fundedbytheauthorsthemselvesand nofundingsourcesmadeanycontributiontoit.

Dataset

• El-Attar, Eman; Khalil, Gihane; Shehata, Gihan; Kandil, Mona; Hassan, Salwa (2017), “Heparin Binding Pro-tein in Acute Bacterial Meningitis”, Mendeley Data, v2 https://doi.org/10.17632/g5c9w4pw3r.2

Conﬂicts

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interest

Theauthorsdeclarenoconﬂictsofinterest.

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