The use of Fuller's earth to reduce acetoacetate interference in the measurement of serum creatinine by the Beckman Astra-4 analyser

Several authors have recently re-emphasized the positive interference of acetoacetate in the measurement of creatinine using the Jaff6 reaction [1-3]. On theoretical grounds, the measurement of creatinine in the presence of acetoacetate should be possible using a kinetic method [4]. In practice, however, measurements by some instruments employing a kinetic Jaff6 method suffer from marked interference by acetoacetate. Haekel described a procedure for the measurement of creatinine in the presence of acetoacetate, utilizing the adsorption of creatinine onto Fuller’s earth, and subsequent simultaneous elution and colour development with alkaline picrate [-5 and 6]. One of the variations of his procedure is that it omits a protein precipitation step [5]. In the present work, the procedure omitting a protein precipitation step has been adapted by eluting creatinine from the Fuller’s earth and measuring the creatinine in the eluate using a Beckman Astra-4 analyser (Beckman RIIC Ltd, High Wycombe, Buckinghamshire HP12 3NR, UK).