AIM: We present two cases with clearly discrepant results of clinical examination and cardiac troponin I (cTnI) and cardiac troponin T (cTnT) concentrations. In similar cases with discrepant results, the possibility of interference should be considered. METHODS: Due to the suspicion of the presence of macrotroponin I in both of the presented cases, the patients were invited to our laboratory and both cTnI (Architect i1000, Abbott) and cTnT (Cobas 8000, Roche) concentrations were analysed. The samples were treated by preincubation in a heterophilic antibodies blocking tube (HBT) and analysed. Precipitation with polyethylene glycol solution (PEG) and molecular weight separation by gel filtration on Sephadex G100 was performed and concentrations of cTnI were analysed. RESULTS: In the same blood sample, the cTnT and cTnI concentrations were 7 and 1782 ng/L, respectively, in Case 1, and 6 and 96 ng/L, respectively, in Case 2. Incubation of samples in HBT had no significant effect. CTnI concentrations after precipitation with PEG - presented as the percentage of initial concentrations - were 7.4% in Case 1 (and 26.8% in the control sample) and 1.4% in Case 2 (and 56.0% in the control sample). These results indicate a significant decrease in both cases, supporting presence of macrotroponin I. Finally, analyses of cTnI concentrations after gel filtration also supported the presence of macrotroponin I. CONCLUSION: The present cases show that the presence of macrotroponin can lead to unnecessary investigation of the patient. When the possibility of interference is suspected, cooperation with laboratory staff to help with interpretation or to perform more detailed analysis is crucial.

Department of Sports Medicine Faculty of Medicine in Pilsen Charles University Prague Pilsen Czech Republic

Faculty of Medicine in Pilsen Charles University Prague Pilsen Czech Republic

Institute of Clinical Biochemistry and Haematology University Hospital in Pilsen Pilsen Czech Republic

Zobrazit více v PubMed

Davidson DF, Watson DJ. Macroenzyme detection by polyethylene glycol precipitation. Ann Clin Biochem 2003;40(5):514-20. DOI

Thygesen K, Alpert JS, Jaffe AS, Chaitman BR, Bax JJ, Morrow DA, White HD and The Executive Group on behalf of the Joint European Society of Cardiology (ESC)/American College of Cardiology (ACC)/American Heart Association (AHA)/World Heart Federation (WHF) Task Force for the Universal Definition of Myocardial Infarction. Fourth universal definition of myocardial infarction (2018). Circulation 2018;138(20):e618-51. DOI

Bohner J, von Pape KW, Hannes W, Stegmann T. False-negative immunoassay results for cardiac troponin I probably due to circulating troponin I autoantibodies. Clin Chem 1996;42(12):2046. DOI

Michielsen ECHJ, Bisschops PGT, Janssen MJW. False positive troponin result caused by a true macrotroponin. Clin Chem Lab Med 2011;49(5):923-5. DOI

Kavanagh L, McKenna TJ, Fahie-Wilson MN, Gibney J, Smith TP. Specificity and clinical utility of methods for the detection of macroprolactin. Clin Chem 2006;52(7):1366-72. DOI

Pettersson K, Eriksson S, Wittfooth S, Engström E, Nieminen M, Sinisalo J. Autoantibodies to cardiac troponin associate with higher initial concentrations and longer release of troponin I in acute coronary syndrome patients. Clin Chem 2009;55(5):938-45. DOI

Aliste-Fernández M, Sole-Enrech G, Cano-Corres R, Teodoro-Marin S, Berlanga-Escalera E. Description of interference in the measurement of troponin T by a high-sensitivity method. Biochem Med (Zagreb) 2019;29(2):021001. DOI

Vafaie M, Biener M, Mueller M, Schnabel PA, André F, Steen H, Zorn M, Schueler M, Blankenberg S, Katus AH, Giannitsis E. Analytically false or true positive elevations of high sensitivity cardiac troponin: a systematic approach. Heart 2014;100(6):508-14. DOI

Adamczyk M, Brashear RJ, Mattingly PG. Prevalence of autoantibodies to cardiac troponin T in healthy blood donors. Clin Chem 2009;55(8):1592-3. DOI

Braun SL, Pongratz DE, Bialk P, Liem S, Schlotter B, Vogt W. Discrepant results for cardiac troponin T and troponin I in chronic myopathy, depending on instrument and assay generation. Clin Chem 1996;42(12):2039-41. DOI

Komrskova J, Franekova J, Jabor A. Macro-complexes and possibilities of their detection. Klinická biochemie a metabolismus. 2019;27(48):172-6. (In Czech)

Lippi G, Cadamuro J, von MA, Simundic AM. Practical recommendations for managing hemolyzed samples in clinical chemistry testing. Clin Chem Lab Med 2018;56(5):718-27. DOI

Mair J, Giannitsis E, Mills NL, Mueller C, Study Group on Biomarkers of the European Society of Cardiology Association for Acute CardioVascular Care. How to deal with unexpected cardiac troponin results. Eur Heart J Acute Cardiovasc Care 2022;11(4):e1-3. DOI

Mair J, Lindahl B, Müller C, Giannitsis E, Huber K, Möckel M, Plebani M, Thygesen K, Jaffe AS. What to do when you question cardiac troponin values. Eur Heart J Acute Cardiovasc Care 2018;7(6):577-86. doi: 10.1177/2048872617708973 PubMed DOI