[1] Univ Porto, Sch Med, Dept Clin Epidemiol Predict Med & Publ Hlth, P-4100 Oporto, Portugal
[2] Univ Porto ISPUP, Inst Publ Hlth, Oporto, Portugal
[3] Hosp Sao Joao Med Ctr, Dept Clin Pathol Serv, Oporto, Portugal
[4] Univ Porto, Sch Med, Dept Biochem, P-4100 Oporto, Portugal
[5] Mario Negri Inst Pharmacol Res, Dept Epidemiol, Milan, Italy
[6] Univ Milan, Dept Med Sci & Publ Hlth, Milan, Italy