STUDY OBJECTIVES: the diagnosis of narcolepsy type 1 (NT1) at its onset in children and adolescents is often difficult, with substantial diagnostic delay. We aimed to test and validate the effectiveness of rapid-eye-movement (REM) sleep latency (REML), the REM sleep atonia index (RAI), and their combination for the automatic identification of pediatric patients with NT1 based on the standard scoring of nocturnal polysomnograms.
METHODS: a retrospective cohort of 71 pediatric patients with NT1 and 42 controls was subdivided in test and validation cohorts. A novel index (COM) was developed as a nonlinear function of REML and RAI. The effectiveness of REML, RAI, and COM in identifying patients with NT1 was assessed with Receiver Operating Characteristic (ROC) curves.
RESULTS: REML, RAI and COM significantly identified patients with NT1 both in the test and validation cohorts. Optimal thresholds that maximized identification accuracy were estimated in the test cohort (REML, 49.5 min; RAI, 0.91; COM, 4.57 AU) and validated in the other cohort. COM performed significantly better in identifying patients with NT1 than either REML or RAI, with ROC area under the curve of 94-100%, sensitivity 85-96%, and specificity 92-100%, and with good night-to-night agreement (Cohen's k = 0.69).
CONCLUSIONS: the analysis of REML, RAI, and particularly their combination in the COM index may help shorten diagnostic delay of NT1 in children and adolescents based on the standard scoring of nocturnal polysomnography.