EVALUATION OF THE I-STAT(TM) SYSTEM - A PORTABLE CHEMISTRY ANALYZER FOR THE MEASUREMENT OF SODIUM, POTASSIUM, CHLORIDE, UREA, GLUCOSE, AND HEMATOCRIT

Objective: To evaluate the analytical performance of the i-STAT(TM) sy stem, which is designed for point of care testing and employs a hand-h eld chemistry analyzer and disposable cartridges, which in the configu ration tested, are capable of measuring sodium, potassium, chloride, u rea, glucose, and hematocrit in approximately 65 mu L of blood in 90 s . Methods: Linearity and imprecision in hematocrit measurement were as sessed using whole blood, while that for the other analytes were evalu ated with aqueous solutions. The accuracy of the i-STAT(TM) system was judged by assay of patient specimens obtained both by venipuncture an d fingerprick and correlated with the Kodak Ektachem 700XR and the mic rohematocrit methods. Results: Linearity was obtained over the clinica lly relevant range for all analytes. Total imprecision as expressed by the coefficient of variation (CV) was less than 3.5% for all analytes at both high and low concentrations except for a low concentration of urea where a CV of 9.4% was obtained. Li near regression analysis rev ealed minimal systematic errors. The standard error about the regressi on line (S-y/x) ranged from 0.017 for hematocrit to 2.262 for chloride in the assay of venous blood, whereas in the assay of capillary blood the S-y/x ranged from 0.018 for hematocrit to 0.755 for glucose. Conc lusions: The analytical performance of the i-STAT was deemed acceptabl e by calculation of total error and comparison with published performa nce standards. Our study has shown the i-STAT(TM) system to be reliabl e, robust, and simple to operate. Moreover, the compactness of the ana lyzer and the requirement for only small volumes of whole blood will m ake it a valuable diagnostic tool in point of care settings.