Suggested immobilization test in RLS clinical trials: A systematic review and methodological appraisal

Area of Science:

• Neurology
• Sleep Medicine
• Clinical Trials

Background:

• Restless Legs Syndrome (RLS) symptoms are assessed using the suggested immobilization test (SIT) in controlled settings.
• The methodological evolution and application of SIT in RLS efficacy trials are examined.
• SIT metrics are compared against conventional outcome measures for RLS assessment.

Purpose of the Study:

• To systematically review the methodological evolution of the suggested immobilization test (SIT).
• To investigate the utilization of SIT in randomized controlled trials (RCTs) for Restless Legs Syndrome (RLS) efficacy.
• To compare the performance of SIT metrics against traditional outcome measures in RLS studies.

Main Methods:

• A systematic review of RLS placebo-controlled RCTs utilizing SIT was conducted across four databases.
• PROSPERO registration (CRD42024542580) and data extraction up to January 2024.
• Cohen's d effect size calculated to compare IRLS, PSG PLMI, SIT discomfort score, and SIT PLMI.

Main Results:

• Nine RCTs were included from 882 screened studies, with most conducted in Europe.
• SIT methodology has evolved since 1988, incorporating multiple tests and a refined discomfort scale.
• SIT PLM index showed superior performance over PSG PLMSI; IRLS had a larger effect size than SIT DS.

Conclusions:

• The suggested immobilization test (SIT) and its modified version (mSIT) robustly assess RLS symptoms.
• SIT/mSIT are underutilized in RLS efficacy trials despite their comprehensive assessment capabilities.
• mSIT offers depth, precision, and complementary data to conventional RLS outcome measures in treatment evaluations.