CrCL, 51-CrEDTA etc.

Date: Mon, 22 Nov 1999 10:01:47 +0000 From: James <J.G.Wright@ncl.ac.uk> Subject: CrCL, 51-CrEDTA etc. Dear Nick, Valdimir, James etc. My personal experience is that the Cockcroft & Gault formula is not very good (at least, in cancer patients, I would not recommend its use). The paper by C&G is vulnerable to criticism from many aspects (4% women, questionable methodology) I am not familiar with the paper by Bjornsson, but if it is from 1979, then we again have to be wary that creatinine assays may have changed a lot since then (and certainly have in my experience). Another problem is that we can't really know the creatinine production, or guarantee that we are in steady-state. We have done some work with surrogate markers and gained a modest improvement over the conventional covariates used (SCr, body size measure, sex, age). If we are trying to generate a surrogate for creatinine production using age, weight and gender, then this may well be population-dependent and before using the Bjornsson formula this would have to be considered careful. Perhaps we can all agree that mechanistic considerations suggest we should reciprocate serum creatinine. James PS 51Cr-EDTA clearance and creatinine clearance don't actually measure the same thing. Which we use depends on the drug (and clinical population) - its the drugs clearance that we need a predictor for (not how much creatinine is in their urine).