Regarding the use of cystatin C for determination of GFR, I had a chat to a woman standing next to a poster at the AACC a couple of weeks ago. It was the poster from abstract 258 in Clin Chem, 45, number 6, Supplement, 1999 concerning the use of cystatin C for this purpose. My memory tells me that the author told me they were using it in children but not adults, but as I review the abstract I wonder if I heard her correctly... A call to Antwerp may help. Graham Jones Staff Specialist in Chemical Pathology St Vincent's Hospital, Sydney %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%