Evaluation of a New System for the Kinetic Measurement of Serum Glutamic

A new spectrophotometric method for the determination of serum glutamic oxalacetic transaminase (SCOT) is described which uses standardized technics and prepackaged reagents. A study was made of this new method in three laboratories and was compared with the routine methods, using identical serum specimens. The new procedure gave good reproducibility and precision. In all methods studied there was evidence of failure of linearity of response at the two highest activity levels examined. IN OIIMAL VALUES in clinical chemistry are dependent upon the age, sex, dietary status, and other characteristics of the population which is examined. Many of the apparent variations in normal ranges from different laboratories are, however, functions of the methodology, technical facility, and differences in reagent preparation, rather than variations in patient population. This is especially true in clinical enzymology where standards for the materials being measured do not exist. Colorimetric technics in enzymology offer procedural ease, but some authors have questioned their reliability (1). Spectrophotometric technics offer increased precision, but are not used in small laboratories because of the instability and cost of the reagents, and the sophistication of instrumentation required. This paper describes a system for the analysis of serum glutamic ovalacetic transaminase * (SOOT) which gives results that are re-producible from laboratory to laboratory. The spectrophotometric technic described is an adaption of that of Henry et a! (2), using a sample of 50 l or less for the 25-mm analysis. This method was com