[1] Vrije Univ Amsterdam, Dept Endocrinol, Ctr Diabet, NL-1007 MB Amsterdam, Netherlands
[2] Univ Amsterdam, Acad Med Ctr, Lab Expt Clin Chem, NL-1105 AZ Amsterdam, Netherlands
[3] Hosp Amstelland, Dept Internal Med, Amstelveen, Netherlands
[4] Hosp Amstelland, Dept Clin Chem, Amstelveen, Netherlands