[Validity and consistency of a new scale (Faces Pain Scale) and of the Spanish version of the CHEOPS scale to evaluate postoperative pain in children]. / Validez y consistencia de una nueva escala (facial del dolor) y de la versión en español de la escala de CHEOPS para evaluar el dolor postoperatorio en niños.

BACKGROUND: one of the most used scales for the evaluation of children's pain is the CHEOPS. This is complex, reliable but not commonly used in spanish. We decided to create a new Pain Facial Scale to be considered to be used in spanish. OBJECTIVE: to compare the validity and consistency of two different scales for the evaluation of post-operative pain in children. METHODS: process, comparative, longitudinal, homodemic, and prolective study. It was elaborated a simple and easy scale, to evaluate the post-operative pain in children. 5 experts evaluated their appearance and content. The original version of CHEOPS was translated to the Spanish by an expert; later this version was corrected and re-translated by a native Anglo-Saxon speaker, the result submitted for evaluation by 5 experts. The validity and consistency of both scales were evaluated by two investigators in a blind way. We used Cronbach's α for the internal consistency of CHEOPS, coefficient of intraclass correlation for the external consistency (inter observer's variability), effect size for sensitivity to the change of category, change of status for internal validity and Spearman's correlation for the convergent analysis. RESULTS: there was great external consistency, and a good and high internal validity, for the Spanish version of the CHEOPS scale, and an excellent internal validity for the Facial Pain Scale, as well as an excellent internal validity for both scales. CONCLUSIONS: two scales can be used to evaluate the post-operative pain in children between 4 and 8 years old.