A Comparison of the i-STAT System and Corning 278 for the Measurement of Arterial Blood Gas Values

Abstract

INTRODUCTION: We compared the performance of a point-of-care measurement system to that of a conventional blood gas analyzer. METHODS: One hundred nineteen arterial blood gas samples from 2 hospitals were analyzed using the i-STAT system and Corning 278 concomitantly. Values were compared using the t test for dependent samples and the Pearson product moment correlations (p < 0.05), and regression equations were calculated to determine the slope and intercept of the regression line for paired values of pH, P_aCO2, and P_aO2. Mean and standard deviations (SD) were also calculated for the difference between the paired results for each variable. RESULTS: Means and SD for the Corning 278 versus the i-STAT for pH were 7.40 (0.06) versus 7.41 (0.07), for P_aCO2 43.0 (9.9) torr versus 43.4 (10.2) torr and for P_aO2 107.9 (73.1) versus 109.7 (76.6) torr. Regression equations were:

i-STAT pH = -0.2174 + 1.0301 × Corning pH

i-STAT P_aCO2 = -0.1724 + 1.0145 × Corning P_aCO2

i-STAT P_aO2 = -2.138 + 1.0373 × Corning P_aO2.

Small, but statistically significant differences between the 2 instruments for pH (p = 0.015) and P_aCO2 (p = 0.017) were obtained but no significant difference for P_aO2 (p = 0.062). Significant correlations between values were obtained with the i-STAT when compared to the Corning 278 for pH (r = 0.9392; p < 0.001), P_aCO2 (r = 0.9804, p < 0.001), and P_aO2 (r = 0.9904, p < 0.001). Mean (SD) differences for the paired results between the 2 systems were -0.005 (0.02) for pH; -0.449 (2.02) torr for P_aCO2, and -1.88 (10.9) for P_aO2. CONCLUSIONS: Results obtained via the i-STAT system correlated well with results obtained with the Corning 278. Small, but statistically significant differences between the 2 instruments on pH and P_aCO2 are probably not clinically important.