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Accepted
for presentation at the Associated Professional Sleep Societies (APSS)
16th Annual Meeting, Seattle WA, June 8-13, 2002. Validation of the KickStrip® : A Novel Screener for Periodic Limb Movements Disorder (PLMD) Shochat T,1 Oksenberg A,2 Hadas N, 1 Molotsky A, 1 Lavie P3 1Scientific Laboratory Products, Ltd., Tel Aviv; 2 Sleep Disorders Unit, Loewenstein Rehabilitation Hospital, Ra'anana; 3 Sleep Medicine Center, Rambam Medical Center, Haifa, ISRAEL Introduction: The KickStrip® disposable diagnostic device for patients suspected of PLMD has been described previously in detail (1). It is based on the "smart sensor" electronic technology, which includes a strain gauge flex sensor, a CPU with real time software, and a display that presents the score (Kscore), which reflects the number of PLM events per hour of use. In the present study, the Kscore is validated against the PLM index (PLMI) based on inlab polysomnography (PSG). Methods: Eighty-two patients (Male/Femal 65/17 age range - 18-74 yrs) suspected of sleep disorders of any kind from two sleep laboratories (31 from Loewenstein Rehabilitation Hospital (LRH) and 51 from Rambam Medical Center (RMC)) participated in the study. All patients underwent an overnight sleep recording with full PSG, including anterior tibialis electromyogram (EMG) concomitantly with a KickStrip® for each leg. Kscores and PLMI (based on standard scoring criteria) from each leg were collected. Analyses were performed for the data of each of the sleep labs and/or both laboratories combined. Analyses were based on all legs beyond patients (LG analysis) and/or on the higher score of the two legs for each patient (PT analysis). Pearson correlations (r) were computed between Kscores and PLMI. Sensitivity (SENS) and Specificity (SPEC) values were computed for various thresholds (>5, >10, >20, >40) representing increasing severity levels of PLMD. For the entire sample only, receiver-operating characteristic (ROC) curves were plotted by LG and area-under-the-curve (AUC) was computed for the various thresholds to determine overall accuracy. A Bland-Altman plot was produced by PT only, to show the distribution of the differences between the Kscores and PLMI against their means. Results: Table 1 shows results for each lab separately and for both combined. Measures of accuracy generally increased with severity level. Figure 1 shows a Bland-Altman plot of the differences between the methods against their means. A mean bias of -1.27 (95% CI -2.9 to 0.37), indicates a slight overestimation of the severity of the PLMD by the KickStrip® . Conclusions: The comparisons between the KickStrip® Kscores and PLMI based on PSG recordings show high correlations and overall accuracy, excellent specificity at all levels, excellent sensitivity at the severe level and medium to good sensitivity in the mild to moderate levels. Clinically, differences between the methods are trivial. We conclude that the KickStrip® is a valuable device for PLMD home screening and for monitoring the efficacy of drug treament. Reference: (1) Shochat T, Molotsky A, Hadas N, Lavie P. (2001) Signal-validation pilot study of the KickStrip: a novel screener for periodic limb movements in sleep (PLMS). Sleep 24 (Suppl):A400. |
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