Negative interference by ethamsylate in enzymatic assay of serum creatinine involving peroxidase-coupled reaction.

and 2.0% for patients’ samples having mean total CO2 of 7 and 35 mmol/L, respectively (n = 27). Least-squares linear-regression analysis of the total CO2 values obtained from the potentiometric (x) and new enzymatic slides (y) for 113 clinical samples (range 15-41 mmol/L) showed the following relationship: y = 0.92 x + 0.35 (r = 0.976, P <0.01) (4). Only samples assayed within 5 miii of each other by the two methods were included in the comparison. Post-production evaluation confirmed the above results: an analytical range of 5-40 mmol/L, and a relationship to the potentiometric method represented by the equation y = 0.93 x + 1.06 (r = 0.971, P <0.01, n = 59). Importantly, nitrate/nitrite did not interfere in the new enzymatic slide, no effect on total CO2 values being noted with as much as 15 mmol/L cerous nitrate added to patients’ sera. Furthermore, we observed no interference from icteric (bilirubin 270 mg/L), lipemic (triglyceride 8850 mgfL), or hemolyzed (hemoglobin 3000 mg/L) samples. The latter finding is notable because some enzymatic total CO2 methods are prone to interference from hemolyzed samples (5). The new enzymatic total CO2 slides were stable for at least 36 days when stored on the Ektachem instrument. Overall, the enzymatic CO2 slide appears to be a viable alternative to the potentiometric method and is not subject to significant nitrate ion interference. It also eliminates the maintenance requirements inherent to potentiometry (and recommended by the manufacturer) such as regular cleaning of the electrolyte reference fluid (ERF) reservoir and warming of the ERF reservoir temperature before use.