Serum creatine kinase isoenzymes

Correct answer = D. The CK isoenzyme pattern at admission showed elevated MB isozyme, indicating that the patient had experienced a myocardial infarction in the previous 12 to 24 hours. [Note 48 to 64 hours after an infarction, the MB isozyme would have returned to normal values.] On day 2, 12 hours after the cardioconversions, the MB isozyme had decreased, indicating no further damage to the heart. However, the patient showed an increased MM isozyme after cardo-conversion. This suggests damage to muscle, probably a result of the convulsive muscle contractions caused by repeated cardioconversion. Angina is typically the result of transient spasms in the vasculature of the heart, and would not be expected to lead to tissue death that results in elevation in serum creatine kinase. 

VoL LVn [6]. Determination of Creatine Kinase Isoenzymes in Human Serum by an Immunological Method Using Purified Firefly Luciferase. A. Lundin. 

Chazan R, Tadeusiak W, Jaworski A, Droszcz W. Creatine kinase (CK) and creatine kinase isoenzyme (CK-MB) activity in serum before and after intravenous salbutamol administration of patients with bronchial asthma. Int J Clin Pharmacol Ther Toxicol 1992 30(10) 371-3. 

ST92 Lianidou, E.S., Christopoulos, T.K. and Diamandis, E.P. (1990). Assay of creatine kinase isoenzyme MB in serum with time-resolved immunofluorom-etry. Clin. Chem. 36, 1679-1683. 

Panteghini M. Serum isoforms of creatine kinase isoenzymes. Clin Biochem 1988 21 211-8. 

Toxicity elevation of serum creatine kinase (CK-MM). In clinical studies (mostly open label), 40% of patients had serum creatine kinase (CK) levels above the upper limit of normal (ULN), and 11% had CK levels that were three times the ULN or more. In cases where CK was fractionated, only the muscle isoenzyme (MM) was elevated. The time to occurrence was sporadic, but the greatest incidence of CK elevation was during the first 2 months of treatment. Elevated CKs were more often seen in males, in patients who were being treated with antidepressants or anti-epileptics, and in patients treated with intrathecal morphine. Most patients who experienced elevations in CK, even for prolonged periods of time, did not have limiting side effects. However, one case of symptomatic myopathy with EMG findings and two cases of acute renal failure associated with rhabdomyolysis and extreme CK elevations (17 000-27 000 lU/L) have been reported. It is recommended that physicians monitor serum CK in patients undergoing treatment with ziconotide periodically. 

The patient, a 63-year-old Caucasian female, was hospitalized on 4 April 2002 though 10 April 2002 for a non-ST segment elevation myocardial infarction (non-Q-wave MI per chart documentation). She had a negative adenosine stress test after the initial event. Her serum cardiac-specific troponin I (cTnl) concentration 24 hours after her onset of chest pain was 1.4 pg/L (upper limit of normal is 0.3 ng/mL), and her creatine kinase (CK) MB level was 12.5 pg/L (upper limit of normal 6.0 ng/mL). Three days post-event her cTnl level was 0.5 pg/L and her CK-MB level was 4.5 pg/L (Fig. 5-1). MB refers to one of the isoenzyme forms of CK found in serum. The form of the enzyme that occurs in brain (BB) does not usually get past the blood-brain barrier and therefore is not normally present in the serum. The MM and MB forms account for almost all of the CK in serum. Skeletal muscle contains mainly MM, with less than 2% of its CK in the MB form. MM is also the predominant myocardial creatine kinase and MB accounts for 10%-20% of creatine kinase in heart muscle. 

Agarose gel electrophoresis (typically 0.7-1 % agarose w/v) is increasingly used in clinical laboratories in place of cellulose acetate, for example in zone electrophoresis of serum proteins, isoenzyme analysis of lactate dehydrogenase and creatine kinase, and immunoelectrophoresis. 

E620 Hadberg, A., Hassager, C., Hildebrandt, P. and Christiansen, C. (1990). Comparison of two immunoinhibitory methods with agarose gel-electrophoresis for measuring the MB isoenzyme of creatine kinase in serum from cases of suspected myocardial infarction. J. Clin. Chem. Clin. Biochem. 28, 453-458. 

E632 Jensen, A.E., Reikvam, A., NordgSrd, Pedersen, K.G. and Asberg, A. (1990). Diagnostic accuracy of Kodak creatinine kinase MB, Stratus creatine kinase MB, and lactate dehyrogenase isoenzyme 1 in serum after acute myocardial infarction. Clin. Chem. 36, 1847-1848. 

ST79 Chapelle, J.-P. and El Allaf, M. (1990). Automated quantification of creatine kinase MB isoenzyme in serum by radial partition immunoassay, with use of the Stratus analyzer. Clin. Chem. 36, 99-101. 

The diagnosis of organ disease is aided by measurement of a number of enzymes characteristic of that tissue or organ. Most tissues have characteristic enzyme patterns (Table 8-2) that may be reflected in the relative serum concentrations of the respective enzymes in disease. The diseased tissue can be further identified by determination of the isoenzyme pattern of one of these enzymes (e.g., lactate dehydrogenase, creatine kinase) in the serum, since many tissues have characteristic isoenzyme distribution patterns for a given enzyme. For example, creatine kinase (CK) is a dimer composed of two subunits, M (for muscle) and B (for brain), that occur in three isoenzyme forms, BB(CKi), MB(CK2) and MM(CK3), which catalyze the reversible phosphorylation of creatine with adenosine triphosphate (ATP) as the phosphate donor ... 

A Glycophase DEAE-CPG column has been used to resolve arylsulfa-tase isoenzymes in serum and in concentrated urine samples from healthy controls, patients with colorectal cancer, and patients with malignant melanoma (B16). Creatine kinase MM and BB isoenzymes in brain and in muscle extracts have been resolved by anion exchange, but the MB isoenzyme was not detected either because of denaturation in the chromatographic process or because of adsorption to the column (KI8). The MB isoenzyme has been successfully detected on a DEAE-Glyco-phase column in the serum of a patient who had suffered a myocardial... 

A4. Aleyassine, M., Tonks, D. B., and Kaye, M., Natural fluorescence in serum of patients with chronic renal failure not to be confused with creatine kinase-BB isoenzyme. Clin. Chem. (Winston-Salem, N.C.) 24, 492-494 (1978). 

Szasz, G., W. Gerhardt, and W. Gruber (1978). Creatine kinase in serum 5. Effect of thiols on isoenzyme activity during storage at various temperatures. Clin Chem 24(9) 1557-1563. 

Agarose gels with concentrations of 0.7-1% (m/v) are often used in clinical laboratories for analysis of serum proteins and isoenzymes of diagnostic importance such as lactate dehydrogenase and creatine kinase. 

Another isoenzyme used diagnostically is creatine kinase (CK), which consists of two types of polypeptide subunits. Subunit B is prevalent in the brain, and subunit M predominates in muscle. Normally CK3 (subunits MM) is present at low levels in the blood serum. However, in a patient who has suffered a myocardial infarction, the level of CK2 (subunits MB) is elevated within 4 to 6 h and reaches a peak in about 24 h. Table 16.10 lists some enzymes used to diagnose tissue damage and diseases of certain organs. 

Serum biomarkers of acute coronary syndrome play a critical role in the diagnosis and risk stratification of patients with ACS. Myocardial necrosis observed in patients with ACS releases a variety of proteins into blood that can be used as biomarkers. Antiquated markers include aspartate aminotransferase, lactate dehydrogenase (LD) and its isoenzyme (LDl), myoglobin, and creatine kinase (CK) and its isoenzyme (CK-MB). While some of these markers are still in routine use, there is consensus among experts in the field of cardiology, emergency medicine, and laboratory medicine that cardiac troponin is the gold standard marker for ACS. 

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