The lack of standardization of cardiac troponin I assay systems.
The lack of standardization of cardiac troponin I (cTnI) assay systems has meant an inability to compare absolute values between methods, and non-traceability of cTnI measurement in clinical laboratories. The present study tested whether a common calibrator for cTnI would harmonize values between different methods. Twenty fresh-frozen plasma samples and a common calibrator were analyzed in duplicate using the Dade Behring Stratus II, Chiron ACS:180, Abbott AxSYM, and Beckman Coulter Access immunoassay systems. Uncorrected cTnI values varied up to 60-fold between systems, and when correlated to the Stratus, linear regression slopes were 0.97 (ACS:180), 4.86 (AxSYM), and 0.03 (Access), verifying the differences in calibration. After correction for calibration differences by reference to the common calibrator, among-assay CV ranged from 2.7% to 55%, and was >25% for eight samples. However, the exclusion of Access results reduced the CV to 32% with only four outliers. The results show that comparable cTnI values between methods are possible by the use of a common calibrator. The lack of method harmonization for some samples may be due to non-equal antibody immunoreactivity of different plasma cTnI forms. The complete standardization of cTnI measurement requires both a secondary reference material and standardization of manufacturers' cTnI antibodies.
Tate
J R
JR
Chemical Pathology Department, Princess Alexandra Hospital, Brisbane, Queensland, Australia. tatej@health.qld.gov.au
Heathcote
D
D
Rayfield
J
J
Hickman
P E
PE
D019963:Clinical Chemistry Tests / Q000592:standards*; D006801:Humans; D009206:Myocardium / Q000378:metabolism*; D011786:Quality Control; D015203:Reproducibility of Results; D019210:Troponin I / Q000097:blood*
D019210:Troponin I