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Introduction Methodology Results Conclusion AST assay on RX daytona plus Reagent on-board stability Conc. U/L Day 1000 900 800 700 600 500 400 300 200 100 0 0 7 14 21 28 Level 1 QC Level 2 QC Level 3 QC Calibrator Level 4 ANALYTICAL EVALUATION OF THE NEW RANDOM ACCESS BENCH TOP ANALYSER RX daytona plus Brown M., McGivern P ., Campbell J., O’Neill G., FitzGerald S.P . Randox Laboratories limited, 55 Diamond Road, Crumlin BT29 4QY, United Kingdom The availability of fully automated clinical chemistry analysers capable of facilitating quick and precise analysis is beneficial in the process of patient diagnosis. This is relevant to those assays used, for example, in the diagnosis of a cardiac event. This study reports the evaluation of a newly developed fully automated bench top system, the RX daytona plus. This is demonstrated with the evaluation of an aspartate aminotransferase (AST) assay. Elevated levels of AST can signal myocardial infarction. For quantitative in vitro determination of aspartate aminotransferase (AST) activity in serum and plasma, the assay kit AST was used (AS8306). The principle of the assay is as follows: Sensitivity and linearity Stability Method Comparison 12/009, 011/AST AST assay on RX daytona plus Limit of Blank (U/L) Linearity (U/L) 0.5 927 Precision 12/012/AST Specimen type n Mean Within-run precision Total precision U/L SD %CV SD %CV Serum Control L2 80 162 2.23 1.4 2.69 1.7 Serum Control L3 80 38 1.14 3.0 1.29 3.4 Serum Pool 80 850 4.57 0.5 11.62 1.4 Serum Pool 80 19 0.43 2.3 1.08 5.8 The assay is applicable to the fully automated RX daytona plus analyser (RX4040). This system requires 5.3µl of neat sample and reagent volumes of 100µl for reagent R1 and 20µl for reagent R2.The first result is generated after 14 minutes and the system includes dedicated software for data management. The assay was performed following the manufacturer’s instructions.The Calibration serum Level 3 (CAL2351) was used. The kit, calibrators, controls, and RX daytona plus analyser were manufactured by Randox Laboratories Limited (Crumlin, United Kingdom). α-oxoglutarate reacts with L-aspartate in the presence of AST to form L-glutamate plus oxaloacetate. α-oxoglutarate + L-aspartate L-glutamate + oxaloacetate AST The indicator reaction utilizes the oxaloacetate for a kinetic determination of NADH consumption. oxaloacetate + NADH + H + L-malate + NAD + MDH Analytical parameters Sensitivity The Limit of Blank was established by testing 120 replicates of a 0.9% saline solution. Statistics detailed in C.L.S.I. guideline EP17-A ‘Protocols for Determination of Limits of Detection and Limits of Quantitation’ were then applied to the data generated to determine the assay Limit of Blank. Limit of Blank (LoB) is the highest measurement result that is exceeded 5% of the time for a blank sample. Linearity The linearity was determined by assessment of replicates of a 10 point linear dilution series of an AST spiked serum sample with an upper limit of 1000U/L. Stability On-board and calibration stabilities were tested by storing one lot of reagent uncapped on the RX daytona plus analyser for a period of 28 days. Precision Within-run and total precision were assessed by testing serum samples at defined medical levels, 2 replicates twice a day for 20 days. Precision estimates were completed according to CLSI documents EP5-A2. Method comparison A method comparison study was conducted by testing 60 serum samples in duplicate using this assay on the RX daytona plus (Y) and on another commercially available clinical chemistry analyser (X). Linear least squares regression was used for the correlation calculation. The data was collected using 5 separate runs over 5 days. • The results from this evaluation indicate optimal analytical performance of the enzymatic IFCC assay for in vitro quantification of AST in serum and plasma samples on the RX daytona plus analyser using liquid assay components. • The easy to use software of this new developed analyser facilitates the input of assay parameters and testing work lists. • Excellent agreement with other commercially available systems. • Low minimum reaction volume of 100µl is required. • 270 photometric tests per hour can be generated. • Overall the system represents a useful cost-effective analytical tool for the clinical chemistry laboratory. Randox Laboratories Limited, 55 Diamond Road, Crumlin, County Antrim, BT29 4QY, United Kingdom T +44 (0) 28 9442 2413 F +44 (0) 28 9445 2912 E [email protected] I www.randox.com 12/009/AST AST Linearity Mean Result U/L Level 1000 900 800 700 600 500 400 300 200 100 0 0 2 4 6 8 10 12 Mean Mean Linear Fit to Levels 1-3 Linear Fit to Levels 2-4 12/010/AST AST: RX daytona plus vs. analyser A RX daytona plus (U/L) Analyser A (U/L) 900 800 700 600 500 400 300 200 100 0 0 200 400 600 800 Y=1.03x + 4.64 r= 0.999 n=120 Range: 0-817 U/L 12/013/AST
