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Multicentre evaluation of the Express Plus clinical chemistry analyzer

The Express-Plus (Chiron, Medfield, USA) is an open, discrete, selective, bichromatic random access clinical chemistry analyzer. The instrument accepts up to 26 reagents on board at one time and assays up to 180 tests per hour for single reagent applications. The analitical performance of the instrument was tested in two hospital laboratories according to ECCLS guidelines for evaluation with respect to imprecision, accuracy, linearity, carry-over, interferences and comparision studies with another instruments. The study comprised 21 analytes including enzymes, substrates, proteins, lipids and electrolytes. The imprecision of the system was acceptable with intra-assay variation coefficients equal or below 4 percent, except for ALT, as well as with inter-assay variation coefficient equal or below 5 percent, except for triglycerides, CK, magnesium, inorganic phosphorus, Apo-A1 and Apo-B, which were slightly higher. Recovery for method assigned control sera values was, with few exceptions, within 5 percent. The manufacturers claims regarding method linearity were as stated or exceeded. No reagent- or specimen-related carry-over was found. Interference studies confirmed influence of hemoglobin on creatinine and glucose, as well as bilirubin on trygliceride, cholesterol, creatinine and glucose, and lipemia on glucose and AST measurement. Comparisson studies were performed on the following analysers: Abbott Spectrum, Beckman Synchron CX4, Olympus AU600, Hitachi 705 and AAS-SP9 and the data statistically processed by Passing & Bablock non- parametric regression procedure. The results showed a high degree of accordance (coefficients of correlation ranging between 0.925 and 0.999). However, statistically signifcant differences for slopes and/or intercepts were found for the following analytes: AST, CK, Apo-A1, albumin, bilirubin, creatinine and iron, which can be explained by differences in the reagent formulation, method employed or calibration. The evaluation showed that Express Plus clinical chemistry analyzer is reliable and overall practicability of the instrument was judged to be satisfactory. It is recomended to be used in small-to-medium size laboratories.

multicentre evaluation ; Express Plus

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