Point-of-Care Measurement of Serum Creatinine in the Intensive Care Unit

Objective: To test the precision and limits of agreement of point-of-care testing (POCT)-based measurement of serum creatinine (Cr) in critically ill patients. Methods: We studied 250 paired blood samples from 82 critically ill patients from a general intensive care unit by simultaneous POCT and central laboratory testing (Jaffe method). Correlation, precision, bias, and limits of agreement were assessed. Possible confounders for interference of noncreatinine chromogens were evaluated by multivariate linear regression analysis. Results: The mean difference in serum Cr measured by central laboratory and POCT was +9.6 mu mol/L (95% limits of agreement: -11.2 to +30.4 mu mol/L). The mean percentage difference between the two techniques was 8.7% (95% limits of agreement -7.8% to +25.1%). On multivariate regression, the difference in serum Cr was increased with greater hemoglobin and lactate levels but decreased with greater bilirubin, albumin, and calcium levels. Conclusions: Compared with the central laboratory testing, POCT-based measurement of serum Cr in critically ill patients carried a small negative bias. This difference appeared affected by the blood levels of biochemical variables known to affect the Jaffe method. POCT-based Cr measurement appears sufficiently accurate for clinical use.