A. Dasgupta et al., Negative interference of bilirubin and hemoglobin in the MEIA troponin I assay but not in the MEIA CK-MB assay, J CL LAB AN, 15(2), 2001, pp. 76-80
Troponin I is a sensitive and specific marker for the diagnosis of myocardi
al infarction. Several commercially available immunoassays measure the conc
entration of troponin I in serum. The microparticle enzyme immunoassay (MEI
A) for troponin I (Abbott Laboratories, Abbott Park, IL) is widely used in
clinical laboratories, including our hospital laboratory. We studied the ef
fect of bilirubin and hemolysis on the MEIA for troponin I and compared our
assay with a newly available chemiluminescent assay (CLIA) for troponin I
(Bayer Diagnostics, Tarrytown, NY). We also measured CK-MB concentration us
ing the MEIA CK-MB assay. One serum pool was prepared by combining several
specimens of one patient with elevated troponin I and with a diagnosis of m
yocardial infarction. Other serum pools were prepared by combining sera wit
h similar troponin I values. All serum pools showed normal bilirubin concen
trations and had no hemolysis. Then we supplemented aliquots of serum pools
with various concentrations of bilirubin (5.0, 10.0, 15.0, and 20.0 mg/dL)
. After supplementation, troponin I concentrations were measured again usin
g the MEIA and CLIA. We observed a statistically significant decrease in tr
oponin I concentration in the presence of bilirubin with the MEIA. For exam
ple, in serum pool 1, the troponin I concentration was 16.3 (bilirubin: 0.8
mg/dL). In the presence of 5.0, 10.0, 15.0 and 20.0 mg/dL of added bilirub
in, the cardiac troponin I concentrations were 13.9, 13.4, 13.3 and 13.0 ng
/ml respectively. We observed similar negative interference of bilirubin in
troponin I measurement by the MEIA in other pools. The troponin I value de
creased slightly (not statistically significant) in one pool and did not ch
ange in two other pools in the presence of bilirubin when we measured tropo
nin I concentration using the CLIA. Interestingly, bilirubin did not interf
ere with the MEIA OK-MB assay. Moderate hemolysis did not have any effect o
n the troponin I assay using either the MEIA or CLIA. However, gross hemoly
sis (hemoglobin > 40 mg/dL) interfered with both assays for troponin I. (C)
2001 Wiley-Liss, Inc.