[1] Univ Milan, Res Ctr Metrol Traceabil Lab Med CIRME, Via GB Grassi 74, I-20157 Milan, Italy
[2] Osped Maggiore Policlin, Fdn IRCCS Ca Granda, Cent Lab, Milan, Italy
[3] St Vincents Hosp, SydPath, Sydney, NSW, Australia
[4] Zuyderland Med Ctr, Dept Clin Chem & Haematol, Heerlen, Netherlands
[5] Univ Hosp Padova, Dept Lab Med, Padua, Italy
[6] Haraldsplass Deaconess Hosp, Norwegian Qual Improvement Lab Examinat Noklus, Bergen, Norway
[7] Univ Bergen, Dept Global Publ Hlth & Primary Hlth Care, Bergen, Norway
[8] Haukeland Hosp, Norwegian Porphyria Ctr, Lab Clin Biochem, Bergen, Norway