|Year : 2020 | Volume
| Issue : 3 | Page : 250-253
High creatine kinase-muscle brain levels greatly exceeding total creatine kinase levels in a 2-month-old infant
Vatsala Khurana, Elvia Jamatia, Reena Rani, Binita Goswami
Department of Biochemistry, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi, India
|Date of Submission||20-Jan-2020|
|Date of Acceptance||28-May-2020|
|Date of Web Publication||05-Oct-2020|
Dr. Elvia Jamatia
Department of Biochemistry, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi - 110 002
Source of Support: None, Conflict of Interest: None
The measurement of creatine kinase muscle brain (CK-MB) by the method of immunoinhibition has various drawbacks, which are posing as a hindrance in its role as a sensitive diagnostic indicator. A 2-month-old infant presented with symptoms of difficulty in breathing and cough. A chest X-ray done showed an incidental finding of a cardiac anomaly, and ultrasonography cranium showed a well-defined cystic lesion seen in the frontal horn of the bilateral lateral ventricle and signs of a resolving hemorrhage. The CK-MB level (761U/L) was greatly exceeding the CK levels (427U/L). This raise in CK-MB may be due to the presence of CK-BB or macro-CK in the plasma. Electrophoresis of the CK enzyme is, therefore, the best way to resolve the shortcomings of immunoinhibition. Macro-CK and CK-BB should hence also be kept in mind when the physician makes a diagnosis on the basis of such a laboratory report.
Keywords: Atypical creatine kinase, creatine kinase-BB, creatine kinase-muscle brain, immunoinhibitionmethod, macro creatine kinase
|How to cite this article:|
Khurana V, Jamatia E, Rani R, Goswami B. High creatine kinase-muscle brain levels greatly exceeding total creatine kinase levels in a 2-month-old infant. Indian J Health Sci Biomed Res 2020;13:250-3
|How to cite this URL:|
Khurana V, Jamatia E, Rani R, Goswami B. High creatine kinase-muscle brain levels greatly exceeding total creatine kinase levels in a 2-month-old infant. Indian J Health Sci Biomed Res [serial online] 2020 [cited 2020 Dec 2];13:250-3. Available from: https://www.ijournalhs.org/text.asp?2020/13/3/250/297194
| Introduction|| |
Creatine kinase (CK) is a dimeric enzyme (82 kDa) that catalyzes the reversible phosphorylation of creatine (Cr) by adenosine triphosphate. CK is widely distributed in tissues, with the highest activity in the skeletal muscle, heart muscle, and brain tissue with much smaller quantities in the bladder, placenta, gastrointestinal tract, thyroid, uterus, kidney, lung, prostate, spleen, liver, and pancreas. Due to the high concentration of CK in the muscle tissue, its levels are seen to be elevated when there is damage to skeletal or cardiac muscle as in cases of myocardial infarction (MI), muscular dystrophy, and rhabdomyolysis. Central nervous system disorders such as strokes, seizures, nerve degeneration, and central nervous system shock also present with a raised level of CK. Because enzyme elevation is found in numerous disorders, the separation of total CK into its various isoenzyme fractions is considered a more specific indicator of various disorders than total levels. Generally, the clinical relevance of CK activity depends more on isoenzyme fractionation than on total levels. The three isoenzymes have been designated as CK-BB (brain type), CK-muscle brain (MB) (hybrid type), and CK-MM (muscle type).
Assay methods for CK isoenzymes are generally divided into the following five categories: Electrophoresis, ion-exchange chromatography, immunoinhibition, immunoprecipitation, and radioimmunoassay. All of these methods are sensitive and specific to CK-MB estimation with varying sensitivity levels of 10 IU/L, l-5 IU/L, and 3 IU/L for electrophoresis, ion-exchange column chromatography, and immunoinhibition, respectively. Of these, electrophoresis is the most reliable and accurate technique but is very time consuming and semi quantitative.
Here, we have utilized the immunoinhibition technique as it is rapid, quantitative, and specific. Currently, immunoinhibition is a widely used method for the estimation of MB isoenzyme of CK in India because of its ability to give faster results in a short period with an autoanalyzer, making it the most feasible to use the method in the emergency laboratory services as it is rapid and quantitative. In this method, antibodies against both the muscle (M) and brain (B) subunits have been used to determine CK-MB activity. Anti-M inhibits all M activity but not B activity. CK activity is measured before and after inhibition. Activity remaining after M inhibition is a result of the B subunit of both MB and BB activity. The residual activity after said inhibition is multiplied by 2 to account for MB activity (50% inhibited). The major disadvantage of this method is that it detects BB activity, which, although not normally detectable, will cause falsely elevated MB results when BB is present. In addition, the atypical forms CK-Mi and macro-CK are not inhibited by anti-M antibodies and may thus cause erroneous results for MB activity.
Here, we present a case of a 2-month-old infant with extremely high CK-MB levels exceeding total CK levels, discuss the various laboratory methods for the evaluation of CK-MB, and possible reasons for its false-positive elevation.
| Case Report|| |
A 2-month-old infant presented with symptoms of difficulty in breathing and cough.
Birth history revealed that he was a preterm vaginal delivery at home delivered in the 6th month of gestation with a birth weight of 1.16 kg. There was a history of neonatal intensive care unit admission for 14 days.
The present weight/height ratio came to be more than the 99th centile. Developmental milestones for age were achieved. On examination, the child was active with a clear chest and normal bilateral breath sounds. The rest of the systemic examination was within the normal limits. The patient was put on oxygen via nasopharyngeal prongs and started on i/v antibiotics Ciprofloxacin and Gentamycin. Regular feeds were given through Ryle's tube as the child was unable to breastfeed adequately.
A chest X-ray was done on the 2nd day of admission, which showed a nonhomogeneous opacity in the right upper and middle zone. There was upper mediastinal widening present may be due to thymus or a cardiac anomaly. Bilateral costophrenic angles were clear.
An ultrasound of the cranium done on the 3rd day of admission showed a well-defined cystic lesion seen in the frontal horn of bilateral lateral ventricle of size 6 mm × 3 mm (both sides) seeming to extend in caudothalamic groove likely a sign of a resolving hemorrhage. The rest of the ventricular system, and posterior fossa was normal. On the 4th day, ciprofloxacin was changed to i/v Ceftriaxone.
The CK-MB level (761U/L) was greatly exceeding the CK levels (427U/L). [Table 1] shows the report of all other blood investigations done for the patient. A provisional diagnosis of pneumonia with anemia was made.
| Discussion|| |
The immunoinhibition, which is currently the most widely used method, may give falsely elevated CK-MB results in the following circumstances:
- The presence of CK BB in the serum can give falsely elevated CK MB values, as seen in healthy infants and children who have physiologically high CK BB levels in comparison to healthy adults. Pathological conditions that can lead to a rise in CK BB may be central nervous system damage, tumors, and childbirth
- Macro CK is another variant that can lead to falsely high CK-MB values by this method. Type 1 macro CK is the immune complex of CK with many types of immunoglobulins. This has been noted for its correlation with autoimmune diseases, especially the myositis group. Type 2 macro CK is a mitochondrion-derived macro CK present in malignancy, especially small-cell lung cancer, gastrointestinal cancer, and colorectal cancer
- CK MM is the main isoenzyme of CK present in skeletal muscles, but 1% is contributed by CK MB also. Hence when skeletal muscle damage occurs, there is an elevation in the absolute levels of CK MM and CK MB, but the relative index (% CK MB) was still <1%
- Mild-to-strenuous activity, intramuscular injections may contribute to elevated absolute CK and CK-MB levels, but the %CKMB (relative index) remains normal. This shows that the source of the rise of this isoenzyme was skeletal muscle and not the cardiac muscle.
In the case presented above, the possible causes of an erroneously elevated CK MB level may be any one or combination of the following:
- As the patient has a history of premature delivery, he might have had neonatal asphyxia making him liable to the presence of type 2 macro CK in his serum, which interfered with CK MB measurement 
- The cystic lesion in his brain suggestive of a resolving hemorrhage may have led to elevated levels of CK BB and its crossing the blood-brain barrier to be present in the patient's serum, an isoenzyme whose presence is believed to be negligible for accurate CK MB estimation by immunoinhibition method 
- Certain lesions of the lungs such as tuberculosis and malignancy, also lead to an elevated CK MB values due to interference by the CK BB isoenzyme.
It is now essential to come up with a better method for evaluation and expression of CK MB levels to obviate the use of unnecessary expensive and invasive diagnostic procedures and misdiagnosis of MI. The various methods which are found in the literature are mentioned below:
- It is suggested that elevated CK-MB levels not consistent with the patient's condition be evaluated with electrophoresis, or better yet, with an immunoprecipitation step before electrophoresis. Immunoprecipitation is another immunological method in addition to immunoinhibition, which uses precipitating antibodies against CK-MM or CK-BB. Although this method is specific and sensitive, it requires a few hours to precipitate immune complexes and, thus, is not recommended for routine analyses in emergency laboratories 
- The solid phase separation techniques, as mentioned and compared with the immunoinhibition method by Gadsden et al. These are highly sensitive and show an excellent correlation with electrophoresis when based on specificity 
- Use of highly specific monoclonal anti-MiCK antibodies as described by Hoshino et al. in order to improve the accuracy of the CK-MB activity assay 
- A radiometric immunochemical method as described by Usategui-Gomez et al., which compared well with CK MB electrophoresis giving a sensitivity of 100% and specificity of 92%
- Certain immune enzyme methods proved to be much better than the immunoinhibition method, as described in a comparative study done by Berny et al.
- It was suggested by Vivekanandan and Swaminathan that reporting %CK-MB rather than the absolute CK-MB results will help in the detection of macroCK (or CK variants) and also improve the reliability of CK MB as a cardiac biomarker.
Physicians need to be made aware of the possible causes of an elevated CK MB value in the absence of cardiac pathologies to avoid wastage of precious time and resources and for the utilization of the prognostic value of variant CK isoenzymes. In such situations, it is recommended to:
- Find out which method was used for the estimation of CK MB
- Get other available cardiac biomarkers evaluated to confirm the diagnosis. (lactate dehydrogenase, troponins, myoglobin, aspartate aminotransferase)
- Take a complete history from the patient to assess the probability of the presence of CK MB/Macro CK in the serum
- Macro CK type 1 is usually present in patients with autoimmune processes, whereas macro CK type 2 is most commonly found in patients with malignant proliferation
- The most common causes of CK-BB elevations are central nervous system damage, tumors, and childbirth.
Confirm the presence of various isoenzymes and atypical forms of CK in the serum by electrophoresis.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Department of Biochemistry, Maulana Azad Medical College, New Delhi.
Conflicts of interest
There are no conflicts of interest.
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