Analytical Concordance of Diverse Point-of-Care and Central Laboratory Troponin I Assays
Albert K Y Tsui1,2, Martha E Lyon3, Sean van Diepen4
1Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada; atsui@ualberta.ca.
Insights
Standardizing cardiac troponin I (cTnI) assays is crucial for acute myocardial infarction diagnosis. A single cutoff value improved concordance across different cTnI testing methods.
Area of Science:
- Clinical Chemistry
- Cardiovascular Diagnostics
- Biomarker Assay Standardization
Background:
- Cardiac troponin I (cTnI) assays are vital for diagnosing acute myocardial infarction (AMI).
- Current 99th percentile cutoffs for cTnI assays lack standardization across different testing platforms.
- This variability hinders consistent AMI diagnosis and patient management.
Purpose of the Study:
- To evaluate the analytical concordance of contemporary cTnI assays with a high-sensitivity assay.
- To assess the feasibility of implementing a single cutoff value for cTnI across various assays.
- To inform the standardization of diagnostic protocols for AMI.
Main Methods:
- Compared 3 point-of-care (POC) and 1 central laboratory cTnI assay against the Abbott high-sensitivity (hs) cTnI assay.
- Analyzed fresh blood samples from 102 coronary care unit inpatients.
- Utilized regression analysis, Bland-Altman plots, and diagnostic contingency tables to assess agreement, correlation, bias, and concordance.
Main Results:
- Most POC cTnI assays showed excellent correlation (r²=0.955-0.970) with the hs-cTnI assay, except for Alere Triage (r²=0.617).
- Proportional bias was observed across all compared cTnI assays.
- Concordance improved from 80-90% at individual 99th percentile cutoffs to 90-95% using a single fixed cutoff (0.03-0.05 ng/mL).
Conclusions:
- Significant analytical discordance exists between cTnI assays at their respective 99th percentile cutoffs.
- A single clinical decision limit for cTnI is supported to standardize diagnostic protocols.
- Despite analytical differences, standardization is feasible and recommended for improved AMI diagnosis.
Background:
Cardiac troponin I (cTnI) 99th percentile cutoffs, used in the diagnosis of acute myocardial infarction, are not standardized across cTnI assays. We compared 3 point-of-care (POC) and 1 central laboratory contemporary cTnI assays against the Abbott high-sensitivity (hs) cTnI to evaluate the analytical concordance and the feasibility of using a single cutoff value for all assays.
Methods:
Fresh blood samples collected from 102 inpatients in the coronary care unit were measured on central laboratory instruments (Beckman Coulter DxI AccuTnI+3 TnI, Abbott Architect hs-TnI) and cTnI POC analyzers (Alere Triage Troponin I, Radiometer AQT90, Abbott i-STAT). Agreement and correlation between the contemporary cTnI assays and hs-cTnI assay were assessed using regression analysis. Proportional bias was assessed using Bland-Altman plots. Concordance between the contemporary cTnI and hs-cTnI assays was determined by diagnostic contingency tables at specific cutoffs.
Results:
Most POC cTnI assays had excellent correlation with the Abbott hs-cTnI method (r 2 = 0.955-0.970) except for Alere Triage (r 2 = 0.617), while proportional bias is evident between all cTnI assays. Overall concordance between POC contemporary cTnI assays and hs-cTnI assay was 80% to 90% at their respective 99th percentile cutoffs. The concordance increased to 90% to 95% when a fixed cutoff of 0.03 to 0.05 ng/mL was used across the assays.
Conclusions:
This study demonstrates poor analytical concordance between cTnI assays at the 99th percentile and supports the notion of a single clinical decision limit for cTnI and consequently standardization of diagnostic protocols despite the analytical differences among these assays.
