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Article published online: 2022-10-17
THIEME
794 Original Article
Validation of ketogenic diet adherence
questionnaire: Keto-check
Validaçãodequestionáriodeadesãoàdietacetogênica:
Keto-check
Lenycia de Cassya Lopes Neri1 Letícia Pereira de Brito Sampaio1
1Universidade de São Paulo, Faculdade de Medicina, Hospital das Address for correspondence LenyciadeCassyaLopesNeri
Clínicas, Instituto da Criança, São Paulo SP, Brazil. (e-mail: lenycia@gmail.com).
Arq. Neuropsiquiatr. 2022;80(8):794–801.
Abstract Background The ketogenic diet is a therapeutic option to control drug-resistant
epileptic seizures and has difficult compliance standards due to adverse effects,
psychosocial factors, or dietary restriction.
Objective To create and validate a ketogenic diet compliance questionnaire.
Methods Methodological study, convergent care. The instrument was analyzed (con-
struct validation) by five judges during two cycles of the Delphi technique. The judges
assessed the relevance and clarity by using the Likert scale with three levels and made
suggestions.Thevalidationoftheinstrumentwascalculatedusingtheagreementrateand
content validity index (CVI). The application by two nutritionists made it possible to test
reproducibility using the Kappa coefficient. When comparing the classification with a
templatedevelopedbythehealthprofessionalswhocaredforthepatientsinquestion,the
Pearson correlation and Fisher exact tests were used. For the reliability test, self-applied
data were collected and evaluated using Cronbach Alpha coefficient.
Results The questionnaire initially created with 11 multiple choice questions on a
Keywords Likert scale was reduced to 10questionswithanagreementrateandtheCVIclassified
► Diet as excellent after two rounds with judges. In the application of the tool, a kappa of
► Ketogenic 0.6087 was obtained, a Pearson that showed no significant difference between
► Surveys and evaluators and a Cronbach α of 0.6483, with substantial consistency.
Questionnaires Conclusions This work resulted in the creation of an unprecedented and reliable
► TreatmentAdherence questionnaire on adherence to the national ketogenic diet. Further studies should be
and Compliance performed to extrapolate the use of this questionnaire in different populations.
Resumo Antecedentes A dieta cetogênica é um tratamento para epilepsia refratária e tem
difícil adesão devido aos efeitos adversos, fatores psicossociais ou à própria restrição
alimentar.
Objetivo Criar e validar um questionário de adesão à dieta cetogênica.
Métodos Estudo metodológico, convergente assistencial. O instrumento foi anali-
sado(validaçãodeconstructo)porcincojuízesdurantedoisciclosdatécnicaDelphi.Os
received DOI https://doi.org/ ©2022.AcademiaBrasileira de Neurologia. All rights reserved.
May24,2021 10.1055/s-0042-1755343. This is an open access article published by Thieme under the terms of the
accepted ISSN 0004-282X. Creative Commons Attribution-NonDerivative-NonCommercial-License,
December22,2021 permitting copying and reproduction so long as the original work is given
appropriate credit. Contents may not be used for commercial purposes, or
adapted,remixed, transformed or built upon. (https://creativecommons.org/
licenses/by-nc-nd/4.0/)
Thieme Revinter Publicações Ltda., Rua do Matoso 170, Rio de
Janeiro, RJ, CEP 20270-135, Brazil
Ketogenic diet adherence questionnaire Keto-check Neri and Sampaio et al. 795
juízesavaliaramapertinênciaeaclarezacomrespostasnaescalaLikertcomtrêsníveis,
alémdesugestões.Avalidaçãodoinstrumentofoicalculadapelataxadeconcordância
e índice de validade de conteúdo (IVC). Posteriormente, houve aplicação por duas
nutricionistas (reprodutibilidade), sendo analisada a concordância pelo coeficiente de
Kappa.Aocompararaclassificaçãocomumgabarito,elaboradopelosprofissionaisda
saúde responsáveis pelos pacientes em questão, foram utilizados os coeficientes de
correlação de Pearson e teste exato de Fisher. Para teste de fidedignidade, a coleta de
dados auto-aplicados foi avaliada pelo coeficiente de Alpha de Cronbach.
Resultados Oquestionárioinicialmentecriadocom11questõesdemúltiplaescolhaem
Keywords escalaLikertfoireduzidopara10questõescomtaxadeconcordânciaeIVCexcelentesapós
► Dieta Cetogênica 2 rodadas com juízes. Na aplicação da ferramenta obteve-se coeficiente de Kappa de
► Inquéritos e 0,6087,ocoeficientedePearsonnãodemostroudiferençasignificativaentreavaliadores,e
Questionários ocoeficiente α de Cronbach de 0,6483, com consistência substancial.
► Cooperação e Conclusões Este trabalho resultou na criação do inédito questionário nacional de
Adesão ao adesão à dieta cetogênica, válido e fidedigno. Outros estudos devem ser realizados
Tratamento para extrapolar a utilização deste questionário em diferentes populações.
INTRODUCTION to adapt to family habits. Children under 1 year of age using
infant formulashouldreceive6mealsaday.Foodisweighed
The ketogenic diet (KD) is a treatment for drug-resistant onadigitalscale.Thedietiscalculatedindividuallyaccording
epilepsy. It is not a recent treatment, having been used for a to body weight, age, and the nutritional status of each child.
hundred years, since 1921. Although currently more wide- Theconsistencymustbemodifiedaccordingtotheoromotor
spread and better implemented, it is still little known by the capacity of each child or use of ostomies.2
general population, including doctors who still consider it a Currently, the protocol for the care of patients with KD is
difficult-to-adhere-to and not a very palatable diet. Since the made by a specialized nutritionist who guides the use of
early 1990s, there has been a dramatic increase in scientific scales to weigh dietary ingredients, guides the way of pre-
articles on KD, and it is now a well-established and proven paring meals and options for substitutions. Even so, in
1,2
effective treatment for epilepsy. clinical practice, patients with greater cognitive capacity
TheKDhasa40to50%chanceofreducingatleast50%of still make mistakes and bring up several questions in the
epilepticseizures.3Itisindicatedforpatientsfromchildhood returns, showing an inability to understand the KD with
toadulthoodwithdrug-resistantepilepsy,oftenwithdailyor theoretical explanations only.
weekly seizures, who have failed treatment with two or Todate,there is novalidated instrument forchecking the
three anti-seizure medications, correctly indicated, tolerat- adherence to KD, and adherence is assessed by the profes-
ed, used in adequate doses in monotherapy or polytherapy sionalteamaccordingtosubjectivemethods.Thus,thisstudy
(3–5). The KD is considered the first line of treatment, has as its primary justification the development and valida-
regardless of the number of epileptic seizures in glucose tion of a questionnaire for adherence to KD.
transporter protein type 1 (GLUT-1) deficiency syndrome
and pyruvate dehydrogenase complex deficiency.3 METHODS
The World Health Organization (WHO) defines as adher-
ence the degree to which a person’s behavior corresponds This is a methodological study of a quantitative nature,
withtherecommendationsofhealthprofessionalsregarding developed in two stages: construction and validation of
medication,dietaryfollow-up,orchangesinlifestylehabits.4 both the content and the reliability and reproducibility of
AdherencetotreatmentinKDisdifficult.Ameta-analysis a questionnaire for adherence to KD, which will be called
with11KDstudiesindicatedacombinedpatientcompliance “Keto-check,” to be applied by the therapeutic team (neu-
of 45%. Adherencefailure is attributed to the adverse effects rologists and nutritionists). In methodological research, the
of the diet, psychosocial factors or the dietary restriction goal is to develop reliable, precise instruments that can be
caused by the diet.5 applied by the multiprofessional team.6,7
TheKDiscomposedoffoodsrichinfat(sourcream,bacon, Thepresentstudywasperformedattheoutpatientclinic
mayonnaise, and oils in general), protein (meat, eggs, of KD, Instituto da Criança, Hospital das Clínicas, Medical
cheese), and a small amount of food that contains carbohy- School of Universidade de São Paulo (ICR-HCFMUSP), from
drates(fruits, vegetables, andgreens). Normally, KDis divid- JanuarytoJuly2020.It wasapprovedbytheResearchEthics
edinto4dailymeals,whichcanvaryfrom3to5mealsaday, Committee (CEP) of the Medical School of Universidade de
Arquivos de Neuro-Psiquiatria Vol. 80 No. 8/2022 © 2022. Academia Brasileira de Neurologia. All rights reserved.
796 Ketogenic diet adherence questionnaire Keto-check Neri and Sampaio et al.
SãoPaulo,withCertificateofPresentationforEthicalAppre- thatthequestioncouldreceiveforrelevanceorclarity.Inthe
ciation (CAAE) 19812919.2.0000.0068 and approval n. third stage, the error of each item is calculated, to discount
3.735.637. possiblebiasesbythejudges.Tocalculatetheerror,one(1)is
Thefirststepwastobuildthecontentoftheinstrument.A dividedbythenumberofjudges,raisedbythesamenumber
brief bibliographic survey was performed on Pubmed with ofevaluators.Inthefourthstep,thefinalCVIofeachitemcan
the terms questionnaire adherence or questionnaire compli- be calculated from the subtraction of the initial CVI by the
anceorquestionnairequalityoflifeandketogenicdietepilepsy error. The acceptable rateofconsensusinthisstudy,foreach
to identify the main parameters that impact adherence to item analyzed to be considered valid, was 90% or CVI of 0.9.
ketogenic therapy. Thevalidationofthecontentofthetoolwentthroughtwo
The tool was initially built by two professionals (nutri- cycleswiththespecialistssothatitcouldreachtheminimum
tionist and child neurologist specialized in KD for epilepsy) value of the CVI for all items. The answers obtained were
with 11 statements related to factors associated with excel- organized in a Microsoft Excel electronic spreadsheet
lent adherencetotreatment:improvement inqualityof life, (Microsoft Corp., Redmond, WA, USA), with the numerical
reduction of seizures, measurement of ketosis, weighing of and subjective information filled in by the judges. In the
foodconsumed,notcheatingonthediet,usingdrugswithout flowchart illustrated in ►Figure 1, all Delphi phases used in
carbohydrates, always attending consultations, reading this study are observed.
labels of processed foods and consulting a nutritionist about
whatyoucanconsume,andcookingathome.Theinterview-
ee should indicate his/her level of agreement with the
statement on a 5-point Likert scale: (1) Strongly disagree,
(2) Partly disagree, (3) I do not know how to answer, (4)
Partly agree, (5) Strongly agree. Each answer would subse-
quently have a score assigned (indicated above in parenthe-
ses) and the sum of all answers would lead to a score
(minimum value 11, maximum 55). The higher the score,
thebetter the adherencetotreatment, beingcategorized as:
insufficient adherence” from 11 to 35 points; good adhesion
from 36 to 45 points; and excellent adhesion from 45 to 55
points.
To validate the instrument, the Delphi technique was
used, with two cycles. (11) The tool was analyzed byagroup Figure 1 Delphi phases used in this study. Source: prepared by the
of experts who acted as judges, composed of five professio- authors. São Paulo. 2020.
nals with the following inclusion criteria: (1) being a doctor
ornutritionist;(2)havingatitleofspecialist,master,orPhD;
and(3)workingintheareasofcare,managementorteaching Table1 Characterizationofthejudgeswhoparticipatedinthe
and research in KD therapy, with more than 10 years of validation of the instrument’scontent
trainingandprofessionalexperience.Theprofessionalswere
invited to participatebye-mail. Wesentaform,preparedon Characteristics n° %
Google Forms, which contained a brief text explaining the Sex F 5 100.0
research and an informed consent form for participation. Total 5 100.0
Next,weprovidedthenewtoolforverificationofadherence Place of São Paulo 2 40.0
toKDwithquestionsinrelationtoeachstatementusedasto professional
the pertinence and ease of understanding. The responses activity Recife 3 60.0
werepresentedonaLikertscalewithascoreof1to3:1¼no; Total 5 100.0
2¼maybe; and 3¼yes. At the end of each question, we Professional Doctorate degree 2 40.0
providedafieldforsuggestions,sothatthejudgescouldgive qualification Master’s degree 1 20.0
feedbackonthequestions,aswellasenrichthecontentwith title
timely aspects.8 Specialization 2 40.0
For content validation, the agreement rate and the con- Total 5 100.0
tent validity index (CVI) werecalculated. Thelatter is widely Knowledge Doctor 1 20.0
used to calculate the consensus among the judges, since it area Nutritionist 4 80.0
measures the agreement about the evaluated aspects.9
The agreement rate was calculated by dividing the num- Total 5 100.0
ber of positive responses by the total number of responses. Professional Assistance 4 80.0
The CVI can be calculated following four steps. The first, practice area Teaching and 120.0
basedonthejudges’scores(1–3),averagesthescoresforeach research
item.Inthesecondstage,basedontheaverage,theinitialCVI Total 5 100.0
for each item is calculated, dividing by the maximum value
Arquivos de Neuro-Psiquiatria Vol. 80 No. 8/2022 © 2022. Academia Brasileira de Neurologia. All rights reserved.
Ketogenic diet adherence questionnaire Keto-check Neri and Sampaio et al. 797
In the first cycle, the five judges responded and made below 0.40 represent low agreement; and values between
suggestions. The tool was reformulated according to opin- 0.40 and 0.75 represent satisfactory agreement.10
ions, after discussion among researchers. The tool for the Without having access to the answers to the question-
analysis of all the judges was sent again. Calculations were naires applied by the nutritionists, two professionals (one
performed, and the consensus initially proposed was doctor and another nutritionist) from the patient care team,
obtained. with access to medical records (laboratory data, ketosis,
After validating the instrument’s content, two nutrition- nutritional status), indicated the correct answers, according
ists, whoworkinthecareareaandwhohadnotparticipated to their knowledge of patient compliance. This was consid-
in the previous stages of the study, were invited to apply the ered the gold standard to compare the correlation of the KD
tool to 10 patients whohaveundergoneorperformedKDfor adherence questionnaire with the perception of the health
at least 3 months, in follow-up at ICR-HCFMUSP. The ques- professional. For that, the statistical test performed for
tionnaire was applied in duplicate by the 2 nutritionists via comparisons between the classifications was the Fisher
telephone, individually, with an interval between applica- exact test, and for the total value of the questionnaire score,
tions longer than 1 week and shorter than 15 days, without it was Pearson correlation coefficient.
thenutritionistshavingaccesstothepreviousanswersofthe To test the reliability of the questionnaire, data was
same patient. The nutritionists were asked to classify collected in a convenience sample from patients using KD.
patients according to the score obtained for the level of The questionnaire was sent electronically for patients and
adherence to KD. To assess the agreement between the caregivers all over Brazil. They self-completed the question-
evaluators (reproducibility), the Kappa coefficient was naire. In this stage, reliability was verified through internal
used, characterized by different ranges, in which values consistency using the Cronbach αcoefficient, which can be
greater than 0.75 represent excellent agreement; values classified as: when it reaches values above 0.8, almost
Table 2 Percentage of agreement (%C) of the judges and the content validity index in the analysis of the instrument
Question Pertinence Clarity
First round Second round First round Second round
1 CVI 0.9997 0.9997 0,8663 0,9997
%C 100 100 60 100
2 CVI 0.9997 0.9997 0.9330 0.9997
%C 100 100 80 100
3 CVI 0.9997 0.9997 0.8663 0.9997
%C 100 100 60 100
4 CVI 0.9997 0.9997 0.9330 0.9997
%C 100 100 80 100
5 CVI 0.9997 0.9330
%C 100 80
6 CVI 0.9997 0.9997 0.9330 0.8663
%C 100 80 80 100
7 CVI 0.9997 0.9997 0.6663 0.9997
%C 100 100 40 100
8 CVI 0.9997 0.9997 0.9330 0.9997
%C 100 100 80 100
9 CVI 0.9997 0.9997 0.9330 0.9997
%C 100 100 80 100
10 CVI 0.7997 0.9997 0.8663 0.9997
%C 60 100 80 100
11 CVI 0.9997 0.9997 0.9330 0.9997
%C 100 100 80 100
Categorization CVI 0.9997 0.9997
%C 100 100
Abbreviation: CVI, Content Validity Index.
%C: Percentage of agreement among judges.
Arquivos de Neuro-Psiquiatria Vol. 80 No. 8/2022 © 2022. Academia Brasileira de Neurologia. All rights reserved.
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