A case report of falsely elevated high-sensitivity cardiac troponin I due to macro-troponin I

This article reports a clinical case of falsely and significantly elevated high-sensitivity cardiac troponin I (hs-cTnI) levels caused by "Macro-Troponin I". A 54-year-old male patient was admitted with a diagnosis of acute non-ST-segment elevation myocardial infarction (NSTEMI). While his hs-cTnI levels rose sharply during the acute phase and subsequently persisted at an extremely high plateau level (>27404 ng/L) without decline for several days, his myoglobin (MYO) and creatine kinase-MB (CK-MB) levels followed the expected pattern of initial elevation followed by resolution. This discrepancy raised suspicion regarding the validity of the hs-cTnI results. Subsequent systematic laboratory verification, including multi-platform assay comparison revealing a vast discrepancy between hs-cTnI and high-sensitivity cardiac troponin T (hs-cTnT) results, non-linear recovery upon serial dilution, and a marked decrease in hs-cTnI to normal levels after polyethylene glycol (PEG) precipitation, confirmed interference from a precipitable macromolecular complex. Furthermore, the interference could not be eliminated by various common heterophilic antibody blocking agents. Based on laboratory results, we confirmed the presence of a macromolecular interference in the patient's plasma, which was highly likely to be macro cardiac troponin I due to its ultra-long half-life.Regarding the origin of macro cardiac troponin I, current research indicates that anti-troponin antibodies exist, which rapidly form immune complexes upon exposure to troponin antigens, thereby interfering with experimental data.Through this case, we demonstrated the presence of macro-complexes interference. The patient ultimately received correct diagnosis and management due to timely recognition of this interference.