Background: Creatine kinase isoenzyme MB (CK-MB) activity using the immunoinhibition method has been
measured in clinical laboratories. However, the presence of mitochondrial CK (MtCK) abnormally increases CK-MB activity
when measured using the conventional method, which can lead to misdiagnosis of acute myocardial infarction
(AMI). A new CK-MB activity assay kit that can inhibit MtCK activity was recently developed; here, we describe the performance
of this kit.
Methods: The analytical performance of this new kit was investigated using 338 samples, and the correlation between results
obtained using the new and conventional kits were analyzed.
Results: A good correlation (r > 0.993) was found between results obtained using the new and conventional kits in the sera
from patients with obvious AMI (n = 91). However, a poor correlation exists between results obtained using the new and
conventional kits in samples from patients without AMI. Electrophoretic CK isoenzyme analysis confirmed that the appearance
of MtCK in nearly all samples from patients with malignant tumors makes poor correlation.
Conclusion: Inhibiting MtCK activity is important for diagnosing AMI. The new method may provide a more accurate
value of CK-MB activity for clinical use.