Validation of the Brazilian Portuguese version of the Stanford cataplexy questionnaire

Cataplexy is a sudden and involuntary episode of loss of muscle tone during wakefulness. Cataplexy cannot be easily recognized when clinical features are atypical or when the physician is unfamiliar with its characteristics. The unstructured clinical interview is the only standard diagnostic method, but the use of a targeted questionnaire can help in the diagnosis of cataplexy. The Stanford cataplexy questionnaire is a self-administered 51-question questionnaire. This validation consisted of an initial translation and back-translation of the questionnaire from English into Brazilian Portuguese, followed by a pilot study with 10 participants for the cultural adaptation of the scale. 155 consecutive patients aged 18–85 completed the questionnaire. The Brazilian version of the Stanford cataplexy questionnaire showed similar results to the original version with good metric properties (area under the curve), high internal consistency (Cronbach's alpha equal to 0.87), good reliability and reproducibility. The Brazilian Portuguese version of the Stanford Cataplexy questionnaire presented good accuracy satisfactory psychometric properties in identifying cataplexy.