Analytical performance evaluation of the Cobas 6000 analyzer - special emphasis on trueness verification

Consolidation of analyzers is an emerging issue in clinical chemistry. We evaluated the analytical performance of the Cobas 6,000 analyzer (Roche Diagnostics), which is considered a candidate for replacement of current Hitachi 917 analyzers and for consolidation of chemistry and immunochemistry.

The precision, accuracy, linearity and correlation with current field methods were evaluated according to Clinical and Laboratory Standards Institute protocols EP5, EP9 and EP10. A total of 31 routine chemistry assays and 18 immunoassays were studied. Accuracy and linearity were verified for 24 chemistry parameters using value-assigned trueness controls from the Dutch External Quality Assessment Scheme organizers. In addition, traceability to methods endorsed by the Joint Committee of Traceability in Laboratory Medicine was examined.

All analytes met allowable precision criteria, apart from the low level for sodium and folate. Total coefficients of variation ranged between 0.6% and 4.4% for routine chemistry and between 0.8% and 5.8% for immunochemistry, apart from folate (12% at the low end). The correlation coefficients for comparison to current field methods were >0.975, except for magnesium and for six out of 18 immunochemistries. Recovery experiments indicated high recovery for most of the 24 routine chemistry assays.

Considering the excellent precision data and the result equivalence for most assays, it can be concluded that Cobas 6,000 accommodates robust chemistry and immunochemistry, and has good potential for workstation consolidation in medium-sized laboratories.