Department of Laboratory Medicine
University of Washington
 
Clinical assay interference and limitations

Methodology: Abbott Axsym Troponin I immunoassay1

Interferences and limitations:

Troponin-I levels can be increased in any condition resulting in myocardial cell damage. For diagnosis of acute myocardial infarction, troponin-I results should be used in conjunction with other information such as other cardiac markers (CK-MB), ECG, clinical observations and symptoms etc. Serial sampling is recommended to detect the temporal rise and fall of troponin-I levels characteristic of acute myocardial infarction.2

The presence of rheumatoid factors or heterophilic antibodies may result in false positive results with the Abbott Axsym Troponin I immunoassay.3,4

Specimens from patients who have received preparations of mouse monoclonal antibodies for diagnosis or therapy may contain human anti-mouse antibodies (HAMA). Such specimens may show either falsely elevated or depressed values when tested with assay kits which employ mouse monoclonal antibodies.5,6 These specimens should not be assayed for Troponin-I using this assay. Please contact the Laboratory Medicine Resident on call 598-6190 if you need to have Troponin-I measured in a patient that has received preparations of mouse monoclonal antibodies.

Clinical specificity in selected groups without myocardial injury (cutoff > 2 ng/mL):1

Skeletal muscle injury: 96.3%
Chronic renal failure: 96.4%
Same day surgery: 96.0%

References:

1. Abbot Axsym Troponin-I assay package insert, 3C29, 1997, Abbott Laboratories.

2. Keffer JH. The cardiac profile and proposed practice guideline for acute ischemic heart disease. Am J Clin Pathol 1997;107:859-860.

3.Fitzmaurice TF, Brown C, Rifai N, Wu AHB, Yeo K-TJ. False increase of cardiac troponin I with heterophilic antibodies. Clin Chem 1998;44:2212-2214.

4. Galambos C, Brink DS, Ritter D, Chung HD, Creer MH. False-positive plasma troponin I with the AxSYM analyzer. Clin Chem 2000 Jul;46:1014-5

5. Schroff RW, Foon KA, Beatty SM, et al. Human anti-murine immunoglobulin responses in patients receiving murine monoclonal antibody therapy. Cancer Res 1985;45:879-885.

6. Primus FJ, Kelley EA, Hansen HJ, et al. "Sandwich"-type immunoassay of carcinoembryonic antigen in patients receiving murine monoclonal antibodies for diagnosis and therapy. Clin Chem 1988;34:261-264.




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Created: February 28, 2002
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