Therapeutic drug monitoring and drugs of abuse testing on the cobas 6000 analyzer series: analytical performance under routine-like conditions.
BACKGROUND
The analytical performance of the clinical chemistry module c 501 (cobas 6000 analyzer series) was evaluated for therapeutic drug monitoring and drugs of abuse testing using a spectrum of representative assays. Particular attention was paid to potential interactions between reagents using a simulated routine workload.


METHODS
Within-run and total imprecision were assessed using a selection of representative reagents. Deviation from a consensus mean was tested using samples from a proficiency testing scheme. Method comparison using routine samples was carried out against the MODULAR ANALYTICS SWA and COBAS INTEGRA 800 analysis systems.


RESULTS
Total coefficients of variation (CV) ranged from 1.9% to 7.8% for individual drugs, and from 3.2% to 8.6% for drugs of abuse testing. Results from proficiency test samples were between 81% and 125% of the consensus mean for therapeutic drugs. Method comparisons (Passing-Bablok regression) showed overall good comparability to MODULAR ANALYTICS SWA and COBAS INTEGRA 800 systems, with slopes from 0.93 to 1.17 and correlation coefficients r > 0.98. Imprecision in a simulated routine run was tested using a total of 42 methods (10 therapeutic drug monitoring, 9 drugs of abuse testing, 3 enzymes, 12 substrates, 8 specific protein assays). Imprecision in the reference batch run ranged from 0.7% to 5.0% CV for therapeutic drug monitoring assays, except for digoxin (DIG) (7.3%), and from 0.9% to 7.7% for drugs of abuse testing. The CVs of general clinical chemistry and specific protein tests were within the expected limits of 2% and 4%. CV changes in the simulated routine run were within the expected limits for most assays. Negative DeltaCVs (> or = 2%) for DIG, digitoxin (DIGIT), cannabinoids (THC), and phencyclidine (PCP) may indicate improved performance when running these assays in a simulated routine operation. A positive DeltaCV (> or = 3%) was found for amphetamines (AMPHs).


CONCLUSIONS
In conclusion, the cobas c 501 module seems to be well-suited for routine use as consolidated workstation. Except for a potential interaction with AMPH, as indicated by the positive DeltaCV, no significant interferences from different reagents could be observed during this study.
Brandhorst
Gunnar
G
Department of Clinical Chemistry, University Hospital Goettingen, Germany. gunnar.brandhorst@med.uni-goettingen.de
Luthe
Hilmar
H
Domke
Ingrid
I
Knoke
Christiane
C
Rhode
Karl-Heinz
KH
Sauter
Heike
H
Oellerich
Michael
M
D002624:Chemistry, Clinical / Q000295:instrumentation / Q000379:methods*; D016903:Drug Monitoring / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D004364:Pharmaceutical Preparations / Q000032:analysis*; D015203:Reproducibility of Results; D015813:Substance Abuse Detection / Q000295:instrumentation / Q000379:methods*
D004364:Pharmaceutical Preparations