1. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Department of Clinical Biochemistry , Echevarne Laboratory , Sant Cugat del Vallés , Spain
2. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Servicio de Análisis Clínicos . Hospital La Paz-Cantoblanco-Carlos III , Madrid , Spain
3. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). External Quality Assurance Programmes , Spanish Society of Laboratory Medicine , Barcelona , Spain
4. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Clinical Laboratories Corporate Manager , Catalan Institute of Health (ICS) , Barcelona , Spain
5. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Servei d’Anàlisis Clíniques , Hospital Universitari Son Espases , Palma , Spain
6. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Department of Clinical Laboratory , University Hospital Germans Trias I Pujol , Badalona , Barcelona , Spain
7. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Unidad extraanalítica , Laboratorios Hospital Universitario Cruces , Baracaldo , Vizcaya , Spain
8. Extra-analytical Quality Commission of the Spanish Society of Laboratory Medicine (SEQC ). Department of Clinical Laboratory , University Hospital Arnau de Vilanova, IRBLleida , Lleida , Spain