Ian Perhaps the following will help To me what is most important is knowing the reference method the creatinine method is aligned with. The largest issue is knowing if both or either are using calibrator values that are traceable to IDMS/MS Most clearance equations were validated with non idms traceable creatinine. This means that if a IDMS creatinine is introduced doing calculations will be impacted This is true regardless if Jaffe or enzymatic For enzymatic the idea of 'no interference' is of course not true. There are far fewer cases however. The US web site NKDEP has helpful information and guidance on back calculations Best wishes and happy new year Joe I ________________________________ From: Clinical biochemistry discussion list <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Sent: Thu Dec 31 06:02:19 2009 Subject: Enzymatic creatinine assay and chemotherapy Dear all We are changing our creatinine assay from a Jaffe based method to an enzymatic assay in the New Year. We have had a query from our Pharmacy about the use of the Cockcroft Gault formula for calculating chemotherapy dosage with creatinine measured by the new assay. What do other laboratories, who also measure creatinine with an enzymatic method, recommend? Best wishes for 2010 Ian Ian Holbrook Department of Clinical Biochemistry York Hospital Wigginton Road York YO31 8HE 01904 725786 ------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content. ACB Web Site http://www.acb.org.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/