Multiplexed Analysis of Human Cytokines by Use of the FlowMetrix System

Abstract

reference values (FastTake ϭ 0.984YSI ϩ 13.3 mg/L, n ϭ 284, S y͉x ϭ 123 mg/L, r 2 ϭ 0.98).By linear regression analysis, results for site 1 compared well to those for site 2. For glucose concentrations measured at site 1, FastTake correlated well with plasma glucose values measured by the YSI (FastTake ϭ 0.987YSI Ϫ 8.4 mg/L, n ϭ 143, S y͉x ϭ 122 mg/L, r 2 ϭ 0.963).Site 2 demonstrated similar linear regression statistics (FastTake ϭ 0.98YSI ϩ 35.6 mg/L, n ϭ 141, S y͉x ϭ 122 mg/L, r 2 ϭ 0.975).Error grid analysis (5) (Fig. 1a) was used to show the clinical accuracy of FastTake for both sites.Over the range of glucose tested, 97.9% of the results fell within zone A (defined as "clinically accurate"), and 2.1% fell within zone B (defined as "deviating from the reference method by Ͼ20% but would lead to benign or no treatment error").Individually, the error grid results were very similar for the two sites, with site 1 and site 2 yielding 97.2% and 98.6%, respectively, in Zone A. For both locations, the remaining data points fell in zone B. During the studies, the clinical performance of the two test strip lots was observed to be identical based on error grid analysis (Fig. 1a).Across the range of observed patient hematocrits (30 -59%), the Fast-Take meter bias relative to the YSI reference was observed to be independent of hematocrit concentration (Fig. 1b).Precision and sample volume testing were conducted at LifeScan to further evaluate the FastTake prototype.Venous whole blood samples were collected from healthy donors in heparinized tubes.Because the product is not intended for use with venous blood samples, to simulate capillary blood, the Po 2 was measured (Ciba Corning Model 278 Blood Gas System, Chiron Diagnostics) and maintained between 60 and 70 mmHg.Precision was evaluated on 2 days using 10 meters and whole blood from two donors.Over the glucose concentrations tested (ϳ500, 800, 1500, 3000, and 5000 mg/ L), within-run precision (CV) ranged from 2.7% to 5.3% (n ϭ 20) for day 1 and 2.8% to 4.6% (n ϭ 20) for day 2.Sample volume testing was also conducted over 2 days by use of five meters and whole blood from two donors.Replicates (n ϭ 3) were tested on each meter at three glucose concentrations (ϳ700, 1800, and 3600 mg/L) with different sample volumes of 2.5, 3, 4, 5, 10, and 25 L. Testing at 2.5 L indicated that 95.6% of the data fell within Ϯ20% of the reference method at the three glucose concentrations tested.For blood volumes of 3.0 L and above, Ͼ97.8% of the laboratory data fell within Ϯ20% of the reference.These studies indicate that the FastTake system provides rapid, accurate, reproducible results in both the laboratory and clinical settings.Although the product is not intended for use with samples containing lower concentrations of oxygen, such as venous blood, the system performance was consistent at sea level and at the lower atmospheric oxygen testing environment encountered in the Denver clinic.System performance in a clinical setting was also found to be consistent throughout the glucose and hematocrit ranges observed.