Decision limit for troponin I and assay performance

Area of Science:

• Clinical Chemistry
• Cardiovascular Diagnostics
• Biomarker Assay Performance

Background:

• Redefinition of acute myocardial infarction (AMI) emphasizes troponin diagnostics.
• New guidelines lower diagnostic cut-offs to the 99th percentile, requiring high assay precision (10% CV).
• The Bayer ACS:180 troponin I assay is evaluated for risk stratification at a 0.1 microg/L cut-off.

Purpose of the Study:

• Assess the appropriateness of the Bayer ACS:180 assay at a 0.1 microg/L cut-off for individual patient risk stratification.
• Determine the functional sensitivity of the troponin I assay.
• Evaluate the impact of sample quality on assay performance.

Main Methods:

• Analysis of assay imprecision at the 0.1 microg/L decision limit.
• Determination of functional sensitivity at 10% inter-assay coefficient of variation (CV).
• Assessment of sample quality by monitoring duplicate precision checks.

Main Results:

• Assay imprecision at 0.1 microg/L could alter risk group assignment for 8% of patients upon re-analysis.
• Functional sensitivity of the ACS:180 troponin I assay was found to be 0.27 microg/L (at 10% CV).
• Poor sample quality, typically fibrin particles, caused 0.39% of routine samples to fail precision checks.

Conclusions:

• Inconsistent risk assessment can occur in a small but significant proportion of cases when using the Bayer assay at 0.1 microg/L.
• Maintaining high sample quality is crucial for reliable troponin I measurements.
• The current performance characteristics of the assay may limit its utility for precise risk stratification at the specified cut-off.