Construção, parâmetros psicométricos e acurácia da escala para suspeição diagnóstica de crises não epilépticas psicogênicas

Abstract

Psychogenic non-epileptic seizure (PNES) is a conversive disorder usually seen in emergency department and neurology services, that diagnosis consists in its distinction from epileptic seizure (ES), which can be a challenge depending on the evaluator’s experience. Diagnosis instruments for PNES can help in identify high risk patients and can provide early referral of these individuals to a video-electroencephalogram (VEEG), the gold standard diagnostic method. In this study, we created a PNES diagnostic suspicion scale – the SSPNES - based in anamnesis data, and we evaluated its psychometric abilities. The development process was realized in three steps: I – Instrument construction; II – Pilot phase; III – Empirical phase. An integrative literature review and the use of a basic theoretical model were essential for the construct adequacy in items. In empirical phase, patients hospitalized for VEEG monitoring participated of this study and were prospectively evaluated by the scale. The final sample consisted of 158 individuals with a mean age of 33 years (SD±12) and with a female sex predominance (66,5%). Participants were divided in two groups: patients with ES (N=103) and patients with PNES or patients with mixed PNES plus ES (N=55). A 15 items final version of SSPNES was created, taking into account statistical data, clinical experience and applicability of the instrument. Item Response Theory (IRT) analysis, using Rasch model and Cronbach’s alpha coefficient of 0.77, confirm the structural validity of SSPNES. When compared to gold standard diagnosis, the scale’s discrimination power was 0.92 (P<0.001, CI 95%: 0.87-0.96) for a score equal or greater than 20 points, which represents an accuracy of 87% of patients. SSPNES instrument created is unprecedented and easy to apply. This study indicates that using 15 specific questions, it is possible to obtain helpful information for suspected PNES, contributing to better care of these individuals with an early referral for VEEG monitoring and suggesting caution in some situations of refractoriness to antiepileptic treatment.