A multicentre evaluation of the Ektachem DT60-, Reflotron- and Seralyzer III systems.

The analytical performance of the three analytical systems Reflotron, Ektachem DT60 and Seralyzer III was studied according to ECCLS guidelines (1) and partly according to a protocol of the Société Francaise de Biologie Clinique (SFBC) (2) in a multicentre evaluation involving four laboratories. The determination of 11 analytes led to more than 180,000 data. With the Ektachem DT60, imprecision was acceptable for all analytes except for sodium. With the Reflotron, imprecision for glucose and creatinine was wider than the acceptable limits. With the Seralyzer III, imprecision for glucose, uric acid, cholesterol, creatinine and potassium was not within acceptance limits. The recovery of system assigned control sera values was acceptable for all analytes, except for glucose, creatinine and sodium with the Ektachem DT60 system, and for all but glucose and cholesterol with the Reflotron. On the Seralyzer III, the limits of acceptance were exceeded only with the creatinine assay. The recovery of the reference method values with Kontrollogen L caused problems with all three systems and for all analytes. Only 30% of the mean values of Kontrollogen L measured with the Ektachem and with the Seralyzer III were within the limits of acceptance. 40% of the mean values determined with the Reflotron were inside these limits. The upper limits of linearity as claimed by the manufacturers were obtained with all analytes and systems with the exception of cholesterol on all systems and the creatinine assay on the Seralyzer III. The systems under test and several different comparison methods showed good agreement for the analysis of patient samples, except in one laboratory for the analysis of sodium and aspartate aminotransferase with the Ektachem system and potassium with the Seralyzer III. Turbidity showed no significant influence on the measurements of all analytes and all systems. Haemolysis, hyperproteinaemia, and bilirubinaemia affected several methods on all three systems. A start time delay of up to 60 s did not affect the results of the Reflotron, except in the case of the triacylglycerol assay, which was affected by start time delays greater than 45 s. The results of 4 assays on the Seralyzer III were decreased considerably by a delayed start time (triacylglycerols and creatinine above 5 s, aspartate aminotransferase above 35 s and creatine kinase above 15 s). For reliable results from all the assays in each of the three analytical systems, it was necessary to use the prescribed sample volume within certain limits. The practicability of all analytical systems tested was found to be very good. A field study was conducted with the Reflotron system. The analyte concentration was determined in venous blood from various patients. In 25 out of 30 experiments, the results of the "field" laboratories showed a greater spread about the fitting line than those obtained in the "expert" laboratories.