www.bjorl.org
Brazilian
Journal
of
OTORHINOLARYNGOLOGY
ORIGINAL
ARTICLE
Comparison
of
the
efficacy
of
vocal
training
and
vocal
microsurgery
in
patients
with
early
vocal
fold
polyp
夽
Hanqing
Wang,
Pan
Zhuge
∗,
Huihua
You,
Yulan
Zhang,
Zhifeng
Zhang
JinhuaCentralHospital,DepartmentofOtolaryngology,Jinhua,China Received20April2017;accepted29March2018
Availableonline9May2018
KEYWORDS
Earlyvocalfold polyp;
Voicetraining; Voicemicrosurgery; Laryngostroboscopy; Voicehandicapindex; Dysphoniaseverity index
Abstract
Introduction:Vocalfoldpolypisabenignproliferativediseaseinthesuperficiallaminapropria ofthevocalfold,andvocalmicrosurgerycanimprovethevoicequalityofpatientswithvocal foldpolyp.Inpreliminarystudies,wefoundthatvocaltrainingcouldimprovethevocalquality ofpatientswithearlyvocalfoldpolyp.
Objective:Thisstudyaimedtocomparetheefficaciesofvocaltrainingandvocalmicrosurgery inpatientswithearlyvocalfoldpolyp.
Methods:Atotalof38patientswithearlyvocalfoldpolypunderwent3monthsofvocal train-ing(VTgroup);another31patientswithearlyvocalfoldpolypunderwentvocalmicrosurgery (VMgroup). Allsubjects wereassessed usinglaryngostroboscopy, voicehandicapindex,and dysphoniaseverity index, andthe efficaciesof vocaltraining and vocalmicrosurgery were compared.
Results:Thecureratesofvocaltrainingandvocalmicrosurgerywere31.6%(12/38)and100% (31/31), respectively. The intragroup paired-sample t-test showed thatthe post treatment vocalhandicapindex,maximumphonationtime,highestfrequency(F0-high),lowestintensity (I-low),anddysphoniaseverityindexinboththeVTandVMgroupswerebetterthanthosebefore treatment,exceptforthejittervalue.Theintergroupindependent-samplet-testrevealedthat theemotionalvaluesofvocalhandicapindex(t=−2.22,p=0.03),maximumphonationtime (t=2.54,p=0.013),jitter(t=−2.11,p=0.03),anddysphoniaseverityindex(t=3.24,p=0.002) intheVTgroupwerebetterthanthoseintheVMgroup.
夽 Pleasecitethisarticleas:WangH,ZhugeP,YouH,ZhangY,ZhangZ.Comparisonoftheefficacyofvocaltrainingandvocalmicrosurgery
inpatientswithearlyvocalfoldpolyp.BrazJOtorhinolaryngol.2019;85:678---84.
∗Correspondingauthor.
E-mail:zhugepandoc@163.com(P.Zhuge).
PeerReviewundertheresponsibilityofAssociac¸ãoBrasileiradeOtorrinolaringologiaeCirurgiaCérvico-Facial. https://doi.org/10.1016/j.bjorl.2018.03.014
1808-8694/©2018Associac¸˜aoBrasileiradeOtorrinolaringologiaeCirurgiaC´ervico-Facial.PublishedbyElsevierEditoraLtda.Thisisanopen accessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).
Conclusions: Both,vocaltraining andvocalmicrosurgerycouldimprovethevoicequality of patientswithearlyvocalfoldpolyp,andthesemethodspresentdifferentadvantages. © 2018 Associac¸˜ao Brasileira de Otorrinolaringologia e Cirurgia C´ervico-Facial. Published by Elsevier Editora Ltda. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
PALAVRAS-CHAVE
Pólipodepregavocal incipiente; Treinamentodevoz; Microcirurgiadavoz; Laringo-estroboscopia; Índicede desvantagemvocal; Índicedeseveridade dedisfonia
Comparac¸ãoentreaeficáciadotreinamentovocaledafonocirurgiaempacientes compólipodepregavocalincipiente
Resumo
Introduc¸ão: Opólipodepregavocaléumadoenc¸aproliferativabenignadacamadasuperficial dalâminaprópriadapregavocal,eamicrofonocirurgiapodemelhoraraqualidadevocaldesses pacientes.Emestudospreliminares,observamosqueotreinamentovocaleracapazdemelhorar aqualidadevocaldepacientescompólipoincipientedepregavocal.
Objetivo: Esteestudo tevecomo objetivo comparar aeficiênciaentretreinamento vocale microfonocirurgiaempacientescompólipoincipientedepregavocal.
Método: Umtotalde38pacientescompólipoincipientedepregavocalforamsubmetidosa trêsmesesdetreinamentovocal(grupoTV);outros31pacientesforamsubmetidosà micro-fonocirurgia(grupoMC).Todososindivíduosforamavaliadospormeiodelaringoestroboscopia, índicededesvantagemvocaleíndicedeseveridadedadisfonia,eaeficáciaentretreinamento vocalemicrofonocirurgiafoicomparada.
Resultados: Astaxas de curado treinamento vocal e damicrofonocirurgia foramde 31,6% (12/38)e100%(31/31),respectivamente.Otestetparaamostraspareadasintragrupomostrou queoíndicededesvantagemvocalpós-tratamento,tempomáximodefonac¸ão,frequência máx-ima,intensidademínimaeíndicedeseveridadedadisfonianosgruposTVeMCforam melho-resdoqueaquelesantesdotratamento,excetopelovalordojitter.Otestetparaamostras independentes intergrupos revelouque o valor emocional do índice de desvantagem vocal (t=-2,22,p=0,03),tempomáximodefonac¸ão(t=2,54, p=0,013),jitter (t=-2,11,p=0,03) eíndicedeseveridadedadisfonia(t=3,24,p=0,002)nogrupoTVforammelhoresdoqueos dogrupoMC.
Conclusões: Tantootreinamentovocalquantoamicrofonocirurgiapodemmelhoraraqualidade davozdepacientescompólipoincipientedepregavocaleessesmétodosapresentamdiferentes vantagens.
© 2018 Associac¸˜ao Brasileira de Otorrinolaringologia e Cirurgia C´ervico-Facial. Publicado por Elsevier Editora Ltda. Este ´e um artigo Open Access sob uma licenc¸a CC BY (http:// creativecommons.org/licenses/by/4.0/).
Introduction
Vocal foldpolyp(VFP) is a benign proliferative diseasein the superficial lamina propriaof the vocal fold; however, thereisnoconsensusregardingtheselectionoftreatment options for this condition. Related studies have indicated thatvocalmicrosurgery(VM)couldimprovethevoice qual-ityofpatientswithVFP,withalowpostoperativerecurrence rate.1---3 However, surgery entails economic burdens,
sur-gical risks, andgeneral anesthesia risks,4 which might be
themain reasons whysomepatients refusesurgery. Vocal therapyincludesvocaltraining(VT)andvocalhealth educa-tion,andstudieshaveshownthatvocaltherapyhascertain therapeuticeffectsonVFP.5,6Comparedwithvocalsurgery,
vocaltherapytakeslonger.Furthermore,inthistreatment approach, the patients’compliancemay beinfluencedby several factors such as low educational level and lack of medicalknowledgeofthepatient;insufficientexperience, inadequatetrainingtime,andineffectivefollow-upof the physician;longpatientwaitingtimeforappointment; incon-venienttravelconditions;andconflictsbetweenthetraining
timeand the work of the patient. Failure of compliance mightresultinadverseimpactsonthetherapeuticeffects andevencause patients toterminate their vocal therapy sessions.7---9
The pathophysiology ofVFP includes primary bleeding, edema,andfibrin deposition.10 Dursunetal.11 found that
comparedwithpatientswithlargepolyps,thejittervalueof patientswithsmallpolypswassignificantlylower.Through multivariate analysis,Cho etal.12 considered that among
such clinical factors as VFP size, location, site of origin, color,andlaryngopharyngealreflux,thepolypsizewasthe onlyfactorrelatedtovocalquality.Inpreliminarystudies, weappliedthe VoiceHandicapIndex (VHI)and Dysphonia SeverityIndex(DSI)toassessthevocalqualityof88patients withearlyVFP(EVFP),andwefoundthatEVFPmanifestedas variousdegreesofsubjectiveandobjectivevocaldisorders. Wealsofound that VTcouldimprovethe vocal qualityof thesepatients,thusconfirmingitsvalueintreatingEVFP.13
Themainpurposeofthisstudywastocomparethe clin-icalefficacies of VTandVM inpatients withEVFP,and to summarizeourclinicalexperience.
Materials
and
methods
Clinicaldata
The study included patients with EVFP treated at the Department of Otolaryngology, Jinhua Central Hospital, fromSeptember 2013toFebruary2015. Theinclusion cri-teria were as follows: (1) Main complaint of hoarseness anddiseasedurationof<6months;(2)Laryngoscopyresults showingthatthepolypwaslocatedat theone-third junc-tionoftheanteromedianvocalfold,appearingasfusiform translucentsmallbump(s)(diameter:less thanone-fourth ofthevocalfold).12Theexclusioncriteriaincludedapolyp
diameter greater than one-fourth of the vocal fold, and pedunculated VFP, vocal fold tumor, vocal nodule(s), or Reinke’sedema.Thirty-eightpatientschosetoundergoVT andvocal health education,and were included in the VT group(groupA).Thirty-one patientsselectedVMfollowed bypostoperativevocalhealtheducationandwereincluded in the VM group (group B). All study subjects signed an informed consent form. This study was conducted with approvalfromtheEthicsCommitteeofJinhuaCentral Hospi-tal(0579-82552825).Writteninformedconsentwasobtained fromallparticipants.
There was no statistically significant difference in sex, age, or occupational vocal usage (Table 1) among the two groups. Subjects with occupational vocal usage included teachers, salespersons, counselors, and tour guides, and their working durations were all >6months.
Laryngostroboscopy
TheXIONlaryngostroboscopysystem(XION,Germany)was used for the inspection. The subjects were seated in a quiet environment and treated with 1% tetracaine spray threetimestoanesthetizethethroatmucosa;subsequently, thesubjectswereasked torelaxandbreathe calmly.The lens was then inserted into the throat, adjacent to the posterior pharyngeal wall and parallel to the vocal fold level. The subjects were asked to pronounce the letter ‘‘I,’’ and the polyp size, location, vibration symmetry, period, amplitude, closure, and mucous membrane fluc-tuations were observed, recorded, and evaluated by the inspector.
Self-subjectiveassessment
Amedicalstaffwasassignedtoexplainthemeaningofthe study tothe subjects, andthe subjects scored the Physi-ological(P), Functional(F), andEmotional (E) sectionsof thequestionnairebyusingtheChineseversionofVHI, with-outassistance.Eachsectionincluded10questions,andthe optionsrepresentedthefrequencyofoccurrenceofthe cor-responding item, as follows: 0 point, ‘‘never’’; 1 point, ‘‘rarely’’;2 points,‘‘sometimes’’; 3 points,‘‘regularly’’; and4points,‘‘always’’.Thescoreofeachsectionwasthe sumof thescores for the10questions, rangingfrom0 to 40points;Totalscore(T)wasthesumofthescoresofthe threesections, ranging from 0 to 120 points. The higher the score in one section, the greater the impact of this sectionon the study subject. The higher theT, themore
severe the VHI according tothe subject’s own subjective assessment.14
Objectiveacoustics,aerodynamicsevaluation,and DSIcalculation
The evaluation wasperformed in one voicetest room by using the DiVAS voiceanalysis software(XION, Germany). Each study subject wore a headset microphone,with the microphone probe 30cm away fromthe subject’s mouth. Afterrelaxingandbreathingcalmly,eachsubjectwastested fortheMaximumPhonationTime(MPT),jitter,Highest Fre-quency(F0-high),andLowestIntensity(I-low),andtheDSI scorewascalculated.
MPTtest:Afterbreathingdeeply,thesubjectsweretold tocontinuouslypronounce thevowel ‘‘a’’witha self-felt comfortabletoneandintensityforaslongaspossible.The testwasrepeatedthreetimesandthelongestvocalsample wasused.
Jitter test: The subjects were told to pronounce the vowel‘‘a’’witha self-feltcomfortabletone andintensity for3s.Thistestwasrepeatedthreetimes.Thejittervalue ofeachpronunciationwithin0.5---1.5swasassessedateach test,andtheaveragevaluewasused.
F0-highand I-lowtest: The subjects weretold to pro-nouncethevowel‘‘a’’withaself-feltcomfortabletoneand intensity,and thisspecific comfortabletone andintensity wererecordedasthebasepoints.Thesubjectswerethen toldtopronouncethevowel ‘‘a’’withashigha toneand intensityaspossible,andthenaslowaspossible,gradually. The averagesofF0-high andI-lowofthethreetestswere used.
TheDSIscorewascalculatedasfollows: DSI=0.13×MPT+0.0053×F0-high
−0.26×I-low−1.18×jitter+12.4.
Surgicalmethods
PatientsintheVM groupunderwentsurgeryperformed by thesame experiencedotorhinolaryngologistundergeneral anesthesiaandamicroscope.Thepolypwasremoved,and themicrostructuresofthevocalfoldwereretainedasmuch aspossible.15---18
Vocaltherapyprotocol
The patientsintheVTgroupreceived3monthsofVTand vocalhealtheducationfromoneexperienced otorhinolaryn-gologist.Eachtrainingcoursewasapproximately60---90min long,andconductedonceevery2weeks.TheVTcontents includedthefollowingactivities:(1)relaxationtraining,2) breathingtraining,(3) vocalposture, (4)balance ofvocal organs,and(5)vocalacoustictraining.Thecontentsofvocal health education included theprevention of vocal misuse andabuse,anduniversalthroathealth knowledge.19---22 All
patientsreceivedthetrainingmaterials preparedbyusto facilitate their continuous practiceat home.Additionally, we alsofollowed-up the patients via telephone to deter-mine their exercise progress and answer their questions. Patients in the VM group were given postoperative vocal healtheducation.
Table1 ClinicalfactorsamongVT,VMandcontrolgroups.
Parameter VTgroup(n=38) VMgroup(n=31) p
Gender,n(%) 0.254
M 12(31.6%) 6(19.4%)
F 26(68.4%) 25(80.6%)
Age(mean±SD;y) 39.71±8.71 36.58±9.65 0.162
Diseaseduration(mean±SD;m) 4.46±1.07 4.74±1.09 0.285
Occupationalvocalusage,n(%) 0.962
Yes 10(26.3%) 8(25.8%)
No 28(73.7%) 23(74.2%)
Table2 Vocalassessmentofthethreegroupsbeforethe treatment.
Parameter VTgroup(¯x ±s) VMgroup(¯x ±s) p
F 9.08±6.94 9.26±8.1 0.922 P 16.03±9.47 18.55±8.57 0.255 E 7.13±8.14 9.13±10.03 0.364 T 30.92±22.48 36.61±25.27 0.326 MPT(s) 16.62±3.47 17.28±3.52 0.441 Jitter(%) 1.41±0.73 1.51±0.63 0.561 F0-High(Hz) 397.66±47.26 375.9±59.35 0.095 I-Low(dB) 56.71±3.42 58.06±4.03 0.136 DSI 0.28±1.18 −0.22±1.43 0.117 Efficacyevaluation
The VTgroup wasreevaluated 1month after theVT (the vocal trainingtime wasthreemonths),and the VM group was reevaluated 4 months after the surgery. Both groups werereevaluatedwithlaryngostroboscopy,withvocalpolyp disappearanceasthecurecriterion,alongwithreevaluation of VHI and retesting of MPT,jitter, F0-high, and I-low to recalculatetheDSI.
Statisticalanalysis
If the data showed normality and homogeneity of vari-ance, they wereexpressed asmean±standard deviation, andintergroupdatawereanalyzedusingthet-test.Ifthe datadidnotshownormalityandhomogeneity ofvariance, theywereexpressedasmedianandquartile,andanalyzed usingtheranksumtest(p<0.05wasconsideredstatistically significant).
Results
Vocalassessment
Laryngostroboscopy revealed that the VFPs inthe VT and VM groups were located at the one-third junction of the anteromedianvocal fold.Therewasnostatistically signifi-cantdifferenceinVHIandDSIinboththeVTandVMgroups beforethetreatment(Table2).
Treatmentefficacies
Thefollow-upexaminationrevealedthatthecureratesof theVTandVMgroupswere31.6%(12/38)and100%(31/31), respectively. The intragroup paired-sample t-test showed thattheposttreatmentVHI,MPT,F0-high,I-low,andDSIin bothtreatment groups showedsignificantimprovement as comparedwiththosebeforetreatment,exceptforthe jit-tervalue(Table3).Amongthe26uncuredpatientsintheVT group,18patientsselectedsurgicaltreatment,whereasthe remaining8patientsselectedvocaltherapysequentially.
Efficacycomparison
The Mann---Whitney U-test revealed that the cure rate of the VM group was better than that of the VT group (Z=−5.792,p=0.000).Theintergroupindependent-sample
t-testrevealedthattheE-value,MPT,jittervalue,andDSI showedgreaterimprovementintheVTgroupthanintheVM group(Table4).
Discussion
PreviousstudiesonthetreatmentofVFPmainlyfocusedon VM,andrelatedreportsproveditseffectivenessforVFP.15---18
ForpatientsunwillingtoundergoVMforvariousreasons,VT mightbeasuitablealternativetreatment.Someresearchers believethatsmallerVFPsareassociatedwithbetterresults ofVTandhealtheducation.23Currently,therehasbeenno
reportcomparingVTandVM inEVFP.Ourfindings suggest thattheposttreatmentvocalqualityofthetwotreatment groups improved by various degrees, which suggests that bothVTandVMwereeffectivetreatmentmethodsforEVFP. The differencesin theprinciplesandcharacteristics of thetwodescribed treatment methodsshould alsobe rec-ognized.Byremovingdiseasedtissues,VMcouldeffectively and quickly resolve the weakening of the mucosal wave causedbycladdingstiffness,aswellasotherconditionssuch aspolyp-inducedglottisincompetence;thus,itimprovesthe patients’ postoperative voicequality. However, VM would undoubtedlyentaileconomicburdensandsurgical risksto patients. Furthermore, surgery alone cannot correct the patients’detrimentalvocalhabits.Theapplicationofvocal educationwouldhelppatientsgainvocalhealthknowledge, thushelpingthemavoid vocalmisuseandabuse,reducing bad vocal behaviors caused by persistent vocal mucosa vibration trauma, and creating conditions for absorption and healing of VFPs. Through continuous practice, the balanceamongvoice-relatedorgans couldbeestablished.
Table3 VocalassessmentofVTandVMgroupsbeforeandafterthetreatment.
Parameter Beforetreatment(¯x±s) Follow-up(¯x±s) t p
VTgroup F 9.08±6.94 5.66±5.4 7.68 0.000 P 16.03±9.47 11.29±8.09 7.47 0.000 E 7.13±8.14 3.95±4.89 5.45 0.000 T 30.92±22.48 20.74±15.93 6.01 0.000 MPT(s) 16.62±3.47 20.09±3.58 −9.11 0.000 Jitter(%) 1.41±0.73 1.13±0.41 4.03 0.000 F0-High(Hz) 397.66±47.26 410.33±49.76 −5.71 0.000 I-Low(dB) 56.71±3.42 54.89±2.9 5.05 0.000 DSI 0.28±1.18 1.63±0.79 −9.38 0.000 VMgroup F 9.26±8.1 6.26±6.35 6.11 0.000 P 18.55±8.57 12.84±6.81 8.51 0.000 E 9.13±10.03 7.77±9.16 6.45 0.000 T 36.61±25.27 26.87±21.63 8.27 0.000 MPT(s) 17.28±3.52 17.78±3.99 −2.66 0.012 Jitter(%) 1.51±0.63 1.38±0.55 3.96 0.000 F0-High(Hz) 375.9±59.35 412.59±45.97 −5.48 0.000 I-Low(dB) 58.06±4.03 55.35±4 8.79 0.000 DSI −0.22 ±1.43 0.78±1.34 −4.12 0.000
Table4 EfficacycomparisonbetweenVTandVMgroupsafterthetreatment.
Parameter VT(¯x ±s) VM(¯x ±s) t p F 5.66±5.4 6.26±6.35 −0.42 0.673 P 11.29±8.09 12.84±6.81 −0.85 0.399 E 3.95±4.89 7.77±9.16 −2.22 0.03 T 20.74±15.93 26.87±21.63 −1.37 0.175 MPT(s) 20.09±3.58 17.78±3.99 2.54 0.013 Jitter(%) 1.13±0.41 1.38±0.55 −2.11 0.038 F0-High(Hz) 410.33±49.76 412.59±45.97 1.85 0.068 I-Low(dB) 56.71±3.42 55.35±4 −0.55 0.582 DSI 1.63±0.79 0.78±1.34 3.24 0.002
Therefore, voicing could be internalized into overall behaviorsandactivities,andpropervoicingpracticescould be learned to improve patients’ objective pronunciation quality, consolidate the therapeutic effects, and prevent VFP recurrence. Therefore, the treatment helps patients clearlyunderstandtheirownvocalproblems,avoidanxiety related to vocal quality disorders, feel their own voice improvements, and establish a rational treatment expec-tation.Furthermore,this helpsin improving thepatients’ self-assessmentofsubjective vocal disorder.Owingtothe differencesincultures,customs,habits,educationallevels, and health-care levels in different regions and countries ---especially thedifferencein phoniatrics--- some Chinese doctorsand patientshave notunderstood thetherapeutic valuesofVTandvocalhealthyet,andthistreatmentoption isworthyofreceivinglargeattention.Juetal.24
systemat-icallystudiedthechangesinacoustics,aerodynamics,and patientself-evaluationofvocaldisorderinpatientswithVFP whoreceivedVTafterVM,andfoundthatVTcouldimprove
thepatients’self-evaluationoftheirpost-VMvocaldisorder. Petrovic-Lazic et al.25 found that the analyzed acoustic
parametersofpatientswithVFPswereimprovedafter pho-nomicrosurgeryandVT,andtendedtoapproachthevalues of thecontrolgroup.This providedgoodclinical evidence andguidanceforareasonableapplicationofVMandVT.
OurresultsshowedthattheimprovementsofMPT,jitter, DSI,andE-valuesintheVTgroupwerebetterthanthatin theVM group.MPTmainly reflectsthe patients’abilityto controltheirownvocalairflow,andjitterreflectsthesmall rapidchangesinfundamental vibrationfrequenciesduring thevocalphonatingprocess,whichcouldreflectthevocal vibrationstabilitytosomeextentbecauseitisinfluencedby vocal foldquality, tension, biomechanicalcharacteristics, innervations,and other factors.Webelieve thatVTcould help improve the patients’ ability to control their vocal airflowandvocalvibrationstability,thusshowingbetterDSI evaluationlevels.VHIisaquestionnairecomposedof func-tional,emotional,andphysiologicalsections,inwhichthe
E-value(emotionalsection)describesvocaldiseases-related emotional responses,andtheassessment resultsmight be influenced by each patient’s character, disease duration, socialstatus,educationallevel,orvocalusageinthesocial setting.26 After VT, patients with VFP could understand
the characteristics of their diseases in a better manner. Moreover, after establishing the correct voicing patterns, patients could regaincomfort during their verbal expres-sion, experience the joy of verbal communication, and calmthementalanxietycausedbyvoicequalitydisorders. This may explain why, in our study, the patients applied vocaltherapyachievedsignificantlyimprovedE-valuesthan those undergoingsurgery. Martines etal.27 alsoindicated
that voice therapy is effective to improve voice quality andtoearlydetectandhelpreduceanxietyanddepression symptoms.Suchsimilarfindingssuggesttheimportant clin-icalvalueof vocaltherapy.On theotherhand,ourresults showedthatwhenthecurestandardwasthedisappearance of VFP under the laryngoscope, the cure rate of the VM group wasmuch better than that of the VTgroup. When physiciansand patientsselect thetreatment method, the curerateisanimportantreferenceindex.Forthepatients withvocalcordpolyps disappearasthetreatment target, surgery seems to bethe preferredmethod. Our research summarizes and compares the subjective and objective vocalchangesofthesetwotreatmentmethods, aswellas thecurerate,soitcanprovideareferenceforpatientsto choosethetreatmentmethodthatsuitstheirownneeds.
Conclusion
Although both VM and VT could effectively improve the vocal qualityofpatients withEVFP, theyrepresent differ-enttreatmentbenefits.Whenphysiciansandpatientsselect theappropriatetreatmentmethod,theyshouldfully under-stand the principles and characteristics of VT and VM. It maybedesirabletoselectatreatmentapproachbasedon thepatients’owndemands,asthiswouldhelpestablish rea-sonabletreatmentexpectations.The limitofourresearch isthatthesamplenumberisnotenough,andthefollow-up timecanbelonger.The main concernreferstothe possi-bilityofselection bias,asthetreatmentgroupswherenot randomized,norstratified.Asthepatientswereallowedfor crosstreatmentarmsaftertreatment,anRCTcouldbean interesting possibility to address this study question with lessbiasedresults.Furtherresearchneedstobecarriedout targetingthesepoints.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
Acknowledgements
ThisstudywassupportedbytheprojectsofZhejiangScience andTechnologyDepartment(n◦ 2011C23129),Keyprojects ofJinhuaMunicipalScienceandTechnologyBureau(n◦ 2011-3-009).
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