Simultaneous presence of IgA- and IgG-CK-BB in a patient without myocardial infarction

Analytical and clinical evaluation of new diagnostic tests for myocardial damage

As with any new test, novel cardiac markers must meet basic analytical and clinical performance issues. For sensitivity and specificity, it is important to know what protein forms are released into blood after injury, and which of these forms are measured by the assays in question. When commercial tests become available, the choice of the measurement platform will be important in the timely delivery of results. The cut-off concentration used is also important, and requires careful selection of the patient groups to be studied. If the intent of the marker is to be used to diagnose acute myocardial infarction (AMI), data from normal subjects should not be included. However, low cut-off limits can be useful for detection of minor myocardial injury if the new assay is highly sensitive and specific. New tests are needed in the area of early diagnosis of AMI, detection of reinfarction or myocardial extension after AMI, risk stratification of patients with unstable angina, and therapeutic monitoring of patients with congestive heart failure. The most promising new markers are glycogen phosphorylase BB, free fatty acid binding protein, and brain natriuretic peptide.

[Macro creatine kinase type 1 as a cause of increase of CF-MB isoenzyme. Apropos of 7 cases]

INTRODUCTION

The macro-creatine kinase type 1 is a complex of IgG linked to the BB fraction of the creatine kinase enzyme. Its presence in serum interferes with the immunoinhibition methods normally used in emergency room laboratories that produce false elevations of the creatine kinase MB isoenzyme, and which may cause a misunderstanding in the evaluation of patients who are suspected of having ischemic cardiopathy.

PATIENTS AND METHOD

We have studied seven patients using an immunoinhibition method. They showed high levels of creatine kinase MB isoenzyme with normal values of creatine kinase enzyme. Electrophoresis was performed on all patients to determine the presence of creatine kinase enzyme.

RESULTS

The electrophoresis showed in all the cases the presence of a macro-creatine kinase type 1 responsible for this interference. The clinical and analytical evaluation, as well as the radiological and electrocardiographical evaluation of this patients did not show any acute coronary disease.

CONCLUSIONS

The macro-creatine kinase type 1 has been related to the existence of underlying cardiovascular pathology; a fact that was confirmed in three patients. With the immunoinhibition methods, the macro-creatine kinases usually, occurs with high values of creatine kinase MB isoenzyme (normally above 50% of the total activity of the creatine kinase) with normal creatine kinase levels. This fact, although strongly suggesting its presence, creates the necessity of using more sensitive methods to prevent these interferences. Likewise, we recommend using the electrophoresis of the creatine kinase enzyme to determine the nature of these interferences.