Factor Analysis of the Brazilian Questionnaire on Adherence to Ketogenic Dietary Therapy: Keto-Check

Background: several strategies are used to assess adherence to ketogenic dietary therapies
(KDTs), the most commonly used being ketonemia or ketonuria, despite their limitations. The
purpose of this article is to carry out an exploratory and confirmatory factor analysis on the proposed
Keto-check (adherence’s KDT Brazilian questionnaire). Methods: there was a methodological study
of a quantitative nature, complementary to the analysis realized previously, with a complimentary
sample. The factorial analysis was performed with Factor software for parallel exploratory analysis,
replicability, and confirmatory factor analysis. Graphical representation was created according to
the number of factors resulting from the analysis. Results: 116 questionnaires were reached by
complementary data collection (n = 69 actual data, complementing n = 47 previous data) through
online forms. A polychoric correlation matrix suitability analysis resulted in a significant Bartlett
statistic (p = 0.0001) and a Kaiser–Meyer–Olkin (KMO) test of 0.56. The parallel factorial analysis
resulted in two factors, graphically represented as “efficacy” and “adherence”. A confirmatory factor
analysis, considered fair, indicated an RMSEA of 0.063, NNFI resulted in 0.872, CFI in 0.926, and GFI
in 0.897. Conclusion: this study confirms the validity of Keto-check through a more detailed analysis.
Adherence is the key to improving the effectiveness of KDTs; therefore, improving knowledge about
it can lead to a better healthcare approach.