We compared the clinical concordance of estimated glomerular filtration rate (eGFR) based on 3 whole blood creatinine assays with the eGFR calculated from a reference plasma creatinine assay. Whole blood creatinine on the Radiometer ABL800 FLEX (Radiometer A/S, Bronshoj, Denmark) demonstrated the best correlation and concordance to plasma creatinine/eGFR compared with the i-STAT (i-STAT, East Windsor, NJ) and StatSensor (Nova Biomedical, Waltham, MA). The i-STAT had better sensitivity (compared with Radiometer) but poorer specificity for prediction of plasma eGFR less than 60 mL/min/1.73 m(2). The StatSensor demonstrated lower concordance of whole blood to plasma eGFR but offered a slope and an intercept offset feature that partially compensates for this effect. The optimal device for use in rapid determination of eGFR from whole blood creatinine may depend on whether it is more important in a given practice to optimize sensitivity, specificity, or overall concordance for determining plasma eGFR less than 60 mL/min/1.73 m(2).