New continuous-flow analysis for simultaneous determination of creatinine and uric acid in 200 microliters of serum without use of a dialyzer

Abstract

We present a new method for direct continuous-flow (AutoAnalyzer II) measurement of serum creatinine and uric acid. The manifold is simple, inexpensive, and can be constructed in the laboratory. Only 200 microliters of serum is needed; analysis rate is 60 samples per hour. The incorporation of sodium dodecyl sulfate and the simultaneous provision of blank subtraction make it possible to omit the dialysis step. Our method does not require the linearizer, since instrument response and concentration of creatinine and uric acid are linearly related to 200 and 120 mg/liter, respectively. The percentages of steady state, interaction, and recovery are acceptable, Precision is excellent and the results obtained from the new method correlate well with those obtained by the comparison methods. Interferences are few and, when encountered, are generally smaller than in the modified Technicon method. Marked hemolysis interferes only with the uric acid assay; marked turbidity has no effect on results for creatinine. Icteric serum with total bilirubin of 50 and 100 mg/liter interferes significantly with results for creatinine and uric acid, respectively, by the new method.