1. Chronic Fatigue Syndrome Unit, Hospital Universitari Vall d´Hebron, Passeig de Vall Hebron 119–129, 08035 Barcelona, Spain.
2. Clinical Trials & Pharmacovigilance Department, Instituto Grifols S.A. Can Guasch 2, 08150 Parets del Vallès, Barcelona, Spain
3. Chronic Fatigue Syndrome Unit, Centro Médico Delfos, Avinguda de Vallcarca 151, 08023 Barcelona, Spain