Clinical Chemistry, Vol 6, 233-242, Copyright © 1960 by the American Association for Clinical Chemistry

Determination of Creatinine in Small Quantities of Plasma

Observations on Two Methods

¹ Clinical Investigation Center, U. S. Naval Hospital, Oakland, Calif.

Two technics for the determination of creatinine in plasma have been described. One consists of an adaptation of the method reported by Van Pilsum, in which certain modifications dealing primarily with the color reaction have been introduced. This method depends on the conversion of creatinine to methylguanidine and employs the Sakaguchi reaction for guanidine groups. It is highly specific and is recommended when accuracy is the predominant requirement. The method has been employed in experimental studies performed on small animals and in renal clearance studies in which the most accurate approximation of glomerular filtration is needed. The appropriate dilution can be made from the original sample if a high creatinine value is anticipated. A second procedure, consisting of an adaptation of the conventional picric acid method, is described. Although less specific, the method is simple, rapid, and can be performed with conventional equipment. It is recommended for routine use.