Analytical Evaluation of the Xpress and Hospital Blood Glucose Monitoring Systems.

Abstract

Diabetes treatment requires self-monitored blood glucose (SMBG), considered an integral part of the therapy.1,2 Therefore, the accuracy of assays performed using glucose meters is of clinical importance. We evaluated the analytical performance of the StatStrip Xpress and the StatStrip Hospital glucose meters utilizing test strips containing glucose oxidase and the amperometric measurement technique (Nova Biomedical, Waltham, MA) including accuracy, imprecision, strips lot-dependent variability, and the hematocrit (HCT) effect. Glucose concentrations were measured in 200 fresh EDTA whole blood samples with glucose concentration from 27 to 401 mg/dL and HCT from 35% to 45% checked using the Sysmex XE-2100 hematology analyzer (Sysmex Corporation, Kobe, Japan). Glucose oxidase method on the chemistry analyzer Maxmat PLII (Maxmat SA, Montpellier, France) was used as a comparator. For the evaluation of the HCT effect EDTA blood samples with glucose concentrations from 31 to 338 mg/dL were used. Adding or removing defined aliquots of plasma prepared the series of secondary samples with HCT from 20% to 60% for glucose measurements.3 Results obtained using both studied glucose meters correlated significantly with each other (r = .99, P < .001, N = 200). The within-run imprecision CVs found for the Xpress and the Hospital were equal to 2.7% and 3.3%, respectively. The between-run imprecision CVs assessed using control materials during the 20-day period amounted to 3.9% and 4.6%, 3.7% and 3.9%, and 2.4% and 3.3% at mean glucose concentration of 61.4 mg/dL, 112.3 mg/dL, and 293.5 mg/dL, respectively. The mean relative lot-dependent difference found for 2 pairs of strips lots was equal to 2.9% and 5.1%. Across the whole range of concentrations (200 samples) both glucose meters yielded higher concentrations as compared to the laboratory method with the positive mean intermethod difference amounting to 5.2% and 2.6%, and the glucose meters error amounted to 2.9% and 2.6%, respectively. The Passing–Bablok agreement test indicated good concordance of results for the Hospital, whereas consistency of the Xpress was poorer. The analysis carried out for 2 groups of samples with glucose < 100 mg/dL and ≥ 100 mg/dL yielded similar results (see Table 1). The error grid analysis yielded all measurement points in zone A and B with 95% and 96.5% of results in zone A, respectively. For glucose concentrations < 100 mg/dL, a bias below ±15 mg/dL was found for 94.7% and for 95.9% of samples, respectively. In the case of 126 samples with glucose ≥ 100 mg/dL, bias below ±15% was found for 95.2% and for 96% of results, respectively. Thus, the accuracy of obtained results meets the ISO 15197:2013 requirements.4 Glucose concentration changes per 1% increase in HCT amounted to −0.17 and −0.46 mg/dL, respectively. Table 1. Comparison of Blood Glucose Concentrations Measured Using the maxmat plii Line Glucose Analyzer and the Xpress and Hospital Glucose Meters. The evaluated meters yielded significantly correlated results fitting the recommendations of the ADA, ISO, and FDA.4,5 The bias from the laboratory method is of minor clinical significance as indicated by the error grid analysis. The HCT effect found for both meters is negligible. Thus, the Xpress and the Hospital can be considered a coherent blood glucose monitoring system suitable for the point-of-care testing and SMBG.