Evaluation of the i-STATTM 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-STATTM system, which is designed for point of care testing and employs a hand-held chemistry analyzer and disposable cartridges, which in the configuration tested, are capable of measuring sodium, potassium, chloride, urea, glucose, and hematocrit in approximately 65 μL of blood in 90 s. Methods: Linearity and imprecision in hematocrit measurement were assessed using whole blood, while that for the other analytes were evaluated with aqueous solutions. The accuracy of the i-STATTM system was judged by assay of patient specimens obtained both by venipuncture and fingerprick and correlated with the Kodak Ektachem 700XR and the microhematocrit methods. Results: Linearity was obtained over the clinically 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. Linear regression analysis revealed minimal systematic errors. The standard error about the regression line (S ) 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 ranged from 0.018 for hematocrit to 0.755 for glucose. Conclusions: The analytical performance of the i-STAT was deemed acceptable by calculation of total error and comparison with published performance standards. Our study has shown the i-STATTM system to be reliable, robust, and simple to operate. Moreover, the compactness of the analyzer and the requirement for only small volumes of whole blood will make it a valuable diagnostic tool in point of care settings.