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False-Positive hs-cTnI in a Patient on Immunotherapy: a Case of Macromolecular Interference
Background:
High-sensitivity cardiac troponin (hs-cTn) is crucial for diagnosing acute coronary syndrome but is susceptible to analytical interference, leading to false-positive elevations (FPE). Macromolecular interferents (e.g., heterophilic antibodies or macrocomplexes) are known causes, especially in immunocompromised patients, such as those receiving immunotherapy [1,2].
Methods:
A 62-year-old male with renal cell carcinoma on toripalimab presented with persistently elevated hs-cTnI levels without clinical signs of myocardial injury. Interference was assessed via polyethylene glycol (PEG) precipitation (using 25% PEG 6000), serial dilution, and alternative platform testing. PEG recovery < 20% indicated macromolecular interference.
Results:
Initial hs-cTnI was 84.4 ng/mL (99th percentile URL = 24.2 ng/mL). Post-PEG, levels fell to 6.7 ng/mL (15.9% recovery), confirming interference. Serial dilution showed non-linearity. An alternate platform returned normal values. Subsequent hs-cTnI results remained normal, supporting transient interference.
Conclusions:
Unexplained hs-cTnI elevations in immunotherapy-treated cancer patients should raise suspicion for macromolecular interference. PEG precipitation, dilution tests, and platform comparisons are effective verifica-tion tools. Clinician-laboratory collaboration is key to preventing misdiagnosis.
