Iron-deficient states can be associated with restless legs syndrome (RLS), and serum ferritin is recommended in screening for iron deficiency in RLS.1 2 Dopamine agonists are first-line treatment for idiopathic RLS, but it is not known if patients’ serum ferritin concentrations influence their responses to these drugs. We wanted to determine if patients with idiopathic RLS with lower serum ferritin (⩽50 μg/l) obtain similar benefit from ropinirole to those with “normal” (>50 μg/l) serum ferritin.2 A post hoc analysis of combined data from two pivotal RLS clinical trials revealed equal benefits of ropinirole over placebo in patients with serum ferritin above or below 50 μg/l.

Patients and methods

Data were pooled from two similarly designed, 12-week, randomised, double-blind, placebo-controlled studies of ropinirole in idiopathic RLS: TREAT RLS 1 and TREAT RLS 2.3 4 Serum ferritin concentrations were obtained at baseline in all patients entering both clinical trials. Subject inclusion and exclusion criteria have been described previously.3 4

Ropinirole 0.25–4.0 mg/day, or placebo, was titrated as needed and tolerated, and taken once a day 1–3 h before bedtime. Patient improvement at week 12 on the International Restless Legs Scale (IRLS) was the primary end point, and the proportion of patients responding to treatment on the Clinical Global Impression – Improvement (CGI-I) …