Owing to the greater use of translated and adapted instruments for measuring oral health on children′s quality of life, there is a need to ensure that such scales (and then items) function in the same way, irrespective of age, sex, socioeconomic status, language, or ethnicity, so they can be used validly and reliably in cross-cultural research. The aim of the present study was to identify whether the Spanish version of the Child Perceptions Questionnaire 11–14 presents differential item functioning.
Child Perceptions Questionnaire 11–14 data from New Zealand (n = 322) and Mexican (n = 335) school-based surveys were compared. Ordinal logistic regression was undertaken in order to identify uniform or non-uniform differential item functioning.
Eleven items showed moderate-to-large uniform differential item functioning in the Spanish version of the Child Perceptions Questionnaire 11–14. Non-uniform differential item functioning was not detected. The psychometric properties of the questionnaire, when removing items showing differential item functioning, showed that the free differential item functioning version was good to excellent.
The Child Perceptions Questionnaire 11–14 Spanish version showed moderate-to-large uniform differential item functioning; however, further research is needed to identify the causes of differential item functioning.