Serial cardiac troponin differences measured on four contemporary analyzers: relative differences, actual differences...

Area of Science:

• Clinical Chemistry
• Biomarker Analysis
• Diagnostic Accuracy

Background:

• Myocardial infarction diagnosis relies on detecting changes in cardiac troponin (cTn) levels.
• Standardizing serial cTn measurements is crucial for accurate diagnosis.
• z-Values offer a method to standardize serial differences by accounting for analytical and biological variation.

Purpose of the Study:

• To investigate the theoretical distributions of actual differences (Δ), relative differences (%Δ), and z-values for cardiac troponin.
• To compare the agreement in classification of cTn differences across four contemporary measurement platforms.

Main Methods:

• Cardiac troponin (cTn) was measured in 575 sample pairs.
• Measurements were performed on Abbott Architect cTnI, Beckman Coulter Access2 cTnI, Roche Cobas cTnT, and Siemens ADVIA Centaur cTnI platforms.

Main Results:

• Good agreement was achieved using a universal z-value cut-off (κ > 0.79) and method-specific fixed Δ cut-offs (κ > 0.82).
• Suboptimal agreement was observed between cTnI and cTnT methods with fixed %Δ cut-offs (κ < 0.50).

Conclusions:

• Fixed Δ cut-offs perform well at low cTn concentrations.
• Fixed %Δ cut-off values are predicted to perform poorly.
• z-Values are concentration-independent, provide a probability continuum, and allow for a universal decision level across cTnI and cTnT methods.