Sleep laboratory diagnosis of restless legs syndrome

Polysomnographic recordings and the Suggested Immobilization Test (SIT) are frequently used to support the clinical diagnosis of restless legs syndrome (RLS). The present study evaluated the discriminant power of 5 different parameters: (1) index of periodic leg movements during sleep (PLMS), (2) index of PLMS with an associated microarousal (PLMS-arousal), (3) index of PLM during nocturnal wakefulness (PLMW), (4) SIT PLM index and (5) mean subjective leg discomfort score during the SIT (SIT MDS) in 100 patients with idiopathic RLS and 50 healthy control subjects. Both groups differed significantly on each parameter studied. Furthermore, while the SIT PLM, the PLMS and the PLMS-arousal indices revealed a poor ability to discriminate patients from controls, the PLMW index and the MDS both showed high sensitivity (87 +/- 7 and 82 +/- 8, respectively) and specificity (80 +/- 11 and 84 +/- 10, respectively) for diagnosing RLS. The combination of these 2 parameters correctly classified 88% of all subjects with a sensitivity of 82% and a specificity of 100%.