An Intradialysis Diagnostic Test for Restless Legs Syndrome: A Pilot Study

Background

Restless legs syndrome (RLS) is common in dialysis patients, but a simple diagnostic test is not available.

Study Design

Diagnostic test study.

Setting & Participants

32 patients with RLS and 29 patients without RLS in 2 dialysis centers.

Index Test

The suggested immobilization test (SIT) was performed during dialysis for at least 30 minutes, and periodic limb movements (PLMs) were assessed by means of electromyography of the anterior tibialis muscles using a Holter monitor as an electromyographic monitoring device. We also assessed changes in number of leg movements on the 30-minute SIT (SIT-PLM) after 4 weeks of treatment with the dopamine agonist pergolide.

Reference Test or Outcome

Clinical review by a neurologist, International RLS Rating Scale (IRLSRS) score, and changes in IRLSRS score after pergolide treatment.

Results

PLMs on the 30-minute SIT during dialysis were identified in 20 of 32 patients with RLS and 3 of 29 control participants. Sensitivity and specificity of PLMs on the 30-minute SIT during dialysis for RLS diagnosis were 63% and 90%, respectively. SIT-PLM correlated with IRLSRS total score at diagnosis (r = 0.53; P = 0.03), suggesting that SIT-PLM measures the general severity of RLS in uremic patients. Treatment with the dopamine agonist pergolide significantly reduced the IRLSRS total score (from a mean of 24.9 ± 9.1 [SD] to 9.5 ± 6.8; P < 0.01) and SIT-PLM (from 41.9 ± 24.2 to 11.3 ± 12.3; P < 0.01), but correlation between changes in SIT-PLM and those in IRLSRS score was not significant (r = 0.27; P = 0.3).

Limitations

Poor correlation may be caused by the small sample size. Time available for the SIT was limited because of the patient's condition during dialysis. Time of day during SIT, mental-alerting activities during SIT, or hemodialysis therapy itself may influence the severity of PLMs.

Conclusions

A Holter-monitored SIT during dialysis is a valid method for the diagnosis of RLS and to evaluate the effect of treatment with pergolide in uremic patients.

Index Words: Restless legs syndrome, uremic, dialysis, periodic limb movements, immobilization, Holter, pergolide