Discrepancy between Cardiac Troponin Assays Due to Endogenous Antibodies
Leo Lam1,2, Lisa Aspin3, Robert Campbell Heron1
1Department of Chemical Pathology, LabPlus, Auckland City Hospital, Auckland, New Zealand.
Clinical Chemistry
|February 8, 2020
Summary
Autoantibodies against cardiac troponin I (cTnI) can interfere with clinical assays, leading to inaccurate results. This study found that macro-cTnI, a common form of these autoantibodies, significantly impacts cTnI assay performance and causes discrepancies between different high-sensitivity assays.
Area of Science:
- Clinical Chemistry
- Immunology
- Cardiovascular Diagnostics
Background:
- Analytical interference from autoantibodies against cardiac troponin (cTn) I is known in experimental settings.
- The impact of these endogenous antibodies on clinical cTn assays has not been systematically studied.
Purpose of the Study:
- To investigate the effects of endogenous autoantibodies on multiple clinical cardiac troponin I (cTnI) and cTnT assays.
- To determine the prevalence and impact of macro-cTnI on cTn assay performance in a clinical setting.
Main Methods:
- Six cTn assays (5 cTnI, 1 cTnT) were used to measure cTn levels in 223 clinical specimens.
- Immunoglobulin depletion using protein A was performed to identify macro-cTnI, with validation by gel filtration and PEG precipitation.
- Assay comparisons were conducted with and without macro-cTnI specimens.
Main Results:
- Macro-cTnI was detected in 55% of the specimens.
- Discrepancies between cTnI assays were reduced after excluding macro-cTnI samples.
- Different slopes were observed in Passing-Bablok regression analysis between hs-cTnI assays for patients with and without macro-cTnI.
- While most macro-cTnI cases did not affect cTnT recovery, 28% showed reduced recovery.
Conclusions:
- The presence of macro-cTnI is a significant factor contributing to observed discrepancies among high-sensitivity cTnI assays.
- Macro-cTnI can impact the accuracy of cTn assays, potentially affecting clinical interpretation.
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