• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

Effect of Macro-Creatine Kinase and Increased Creatine Kinase BB on the Rapid Diagnosis of Patients With Suspected Acute Myocardial Infarction in the Emergency Department

Posted on: Saturday, 20 August 2005, 03:00 CDT

Although there are more sensitive and earlier diagnostic markers for the diagnosis of acute myocardial infarction (AMI), measurement of creatine kinase (CK) MB isoenzyme (CKMB) using the immunoinhibition method is still widely used in stat laboratories. In this study, 3,290 patients with the prediagnosis of AMI underwent physical examinations, electrocardiography, and repetitive measurements of CK, CKMB activity, and CKMB mass, and 304 of them were diagnosed as having AMI. Electrophoresis of CK and CKMB mass was performed for the samples from 415 patients whose CKMB activity values were found to be increased and were not correlated with total CK levels. According to CKMB activity, CK electrophoresis, and CKMB index (100 CKMB activity/CK) values, macro-CK (MCK) and/or increased CKBB levels were detected in 27 cases (MCK-I in 10 cases, MCK-II in 9, increased CKBB in 5, and both MCK-II and increased CKBB in 3). CKMB activity was found to be increased for all except one patient (96.3%), and the CKMB index was >25% in 25 (92.5%) of 27 cases. CKMB mass values were within the normal range in 25 of the cases with MCK. Two patients with MCK-I were diagnosed as having AMI because of increased CKMB mass and positive electrocardiography findings. The incidence of MCK and/or high CKBB levels (0.82%) in the whole group was similar to that reported for a normal population. MCK existence and increased CKBB levels may cause misleading diagnoses if CKMB mass measurements and/or CKMB index values are not used together for patients with suspected AMI.

Introduction

The term acute coronary syndrome refers to ischemic processes involving myocardium, ranging from angina, unstable angina, or myocardial infarction (MI) to extensive tissue necrosis. These disorders have principally been assessed by means of symptoms, electrocardiography(ECG), and the use of some biochemical markers reflecting the status of the myocardium, in accordance with the recommendations of the World Health Organization after their introduction. Although it is not specific to myocardium, creatine kinase (CK) and the MB isoenzyme (CKMB) (EC 2.7.3.2) have been the most promising biochemical markers of myocardial injury in the past. CKMB levels, in combination with myoglobin levels and physical signs of the patient, have been used to evaluate the course of reperfusion after thrombolytic therapy. Recently, cardiac isoforms of troponin T and I were reported to be highly sensitive markers of MI and good candidates for risk stratification of patients with acute coronary syndrome. However, some promising markers, such as C-reactive protein and serum amyloid A, glycogen phosphorylase-BB isoenzyme, and soluble fibrin, seem to have potential use in the near future for the prediction of plaque disruption, ischemia, and thrombosis risk, respectively. Biochemical markers directed toward diagnosis of MI, determination of coronary risk, and monitoring of the reperfusion state are expected to gain more significance in parallel with future scientific advances.1-3 However, measurements of total CK activity and its MB fraction are still the most commonly used tests in the stat laboratory, despite the previous introduction of more sensitive and earlier diagnostic markers for MI, such as CKMB mass, cardiac troponin T, cardiac troponin I, and myoglobin, for cost and/or technical reasons.3-7

CK is composed of three different isoenzymes, which are formed of two subunits (M refers to muscle and B refers to brain) with the molecular mass of ~ 80 kDa for each moiety, catalyzing the phosphorylation of creatinine irreversibly (CK-1or CKBB, CK-2 or CKMB, and CK-3 or CKMM).7 CKBB is mainly found in brain, prostate, intestine, lung, urinary bladder, uterus, placenta, and thyroid. CKMM and CKMB are present in both skeletal and cardiac muscle. CKMB accounts for 25 to 46% of total CK activity in cardiac muscle and is found in a very small amount in skeletal muscle.7,8

Some studies reported two atypical variants of macro-CK (MCK) with a considerably greater molecular mass (>200 kDa). MCK type I (MCK-I) generally occurs as a result of the formation of immune complexes between the CKBB isoenzyme and the light chain of monoclonal IgG. However, MCK type II (MCK-II) is determined electrophoretically within the section close to the cathode.910

Therefore, in cases with MCK, indirect inhibition may give rise to false-positive high CKMB activity, because of the increase in the neglected CKBB fraction.10-12 Studies on CKBB and MCK carried out with subjects with possible acute MI (AMI) are limited, although investigations of MCK incidence in broad populations have been performed. In this study, patients admitted to the emergency care unit with clinical suspicion and ECG findings were diagnosed as having MI according to ECG, clinical, and biochemical findings. Thereupon, this study also aimed to perform serum CK electrophoresis and CKMB mass measurements for cases where CKMB and CK were not thoroughly correlated and to investigate false-positive tests of MCK and CKBB and their effects on diagnosis.

Methods

For this study, 3,290 patients with clinically suspicious conditions (age, 28-86 years; 922 female subjects and 2,368 male subjects) who had been admitted to the Emergency Department of Glhane Military Medical Academy and hospitalized between March 1999 and January 2002 were accepted. According to World Health Organization criteria for the diagnosis of MI,1,13 these subjects were evaluated with ECG studies, serum total CK and CKMB levels were measured at least 4 to 6 hours after angina onset, and the activities of these enzymes were determined every 4 to 6 hours until the diagnosis became accurate. cases with cardiogenic shock, cardiac arrest, deflbrillation, or angina for >24 hours were not included in the study. The patients with abnormal CK and CKMB values were separated into groups, i.e., those with definite MI, those who underwent follow-up monitoring after coronary surgery,14 those with well-known muscular pathology, and those with MCK and CKMB increases. In addition, to evaluate MCK and CKBB levels, CK electrophoresis was carried out for 415 subjects who had high enzyme activities of CK and CKMB and an abnormal CKMB index [CKMB index = 100 (CKMB activity/CK)].

CK activity was measured with an Hitachi 917 autoanalyzer at 37C by using a commercially available CK N-acetylcysteine kit (Boehringer Mannheim, Mannheim, Germany). Normal values of CK in serum are <190 U/L.

For the immunoinhibition CKMB assay, serum samples were incubated with reagent containing antibody against CK M subunits, which were completely inhibited. Creatinine phosphate was added to start the reaction, and residual CK B subunit activity was measured (normal values in serum are <25 U/L). The reagent used for the assay was CKMB N-acetylcysteine (Boehringer Mannheim). CKMB mass assays were carried out with an ADVIA Centaur analyzer (Bayer Corporation, Tarrytown, New York) using direct chemiluminometric immunoassay technology where constant amounts of two antibodies were used.

Fig. 1. Electrophoretic patterns of MCK-I, MCK-II, and CKBB.

CK electrophoresis was performed with a Titan Gel PC-CK isoenzyme kit (Helena Laboratories, Beaumont, Texas). This application was evaluated by the electrophoretic separation of CK fractions on agarose gels and screening in fluorescence mode with an electrophoresis data center densitometer (Helena Laboratories). A control marker containing CKMM, CKMB, and CKBB was used for each run.

Results

Of 3,290 patients whose total CK and CKMB activities were measured after clinical and ECG findings, 304 (9.24%) were diagnosed as having an AMI and were given the required treatment. According to the results of CK electrophoresis applied to the samples in 415 cases in which CK and CKMB levels were high and the CKMB:CK ratio was abnormal, MCK-I and MCK-II were determined in the samples from 10 and 12 patients, respectively, and 5 patients had increased CKBB activity. For two subjects with MCK-II, CKBB activity was found to be increased. The electrophoretic appearance of CK isoenzymes for patients with MCK-I and MCK-II and high CKBB activity is shown in Figure 1. Clinical and analytical data obtained for these patients are given in Table I.

Activity levels of CKMB were found to be increased for 381 (11.6%) of 3,290 patients, but 282 (92.8%) of 304 patients with AMI were found to have higher CKMB levels. Although the other 22 patients with AMI showed an increasing trend in the levels of CKMB activity measured within the first 12 hours, this result was not above the cut-off value. From this point of view, they were finally diagnosed as having an AMI with the evaluation of ECG findings, clinical status, ongoing increases in CKMB activity and CKMB mass, and other criteria related to AMI. They were also assessed with the tests (CKMB activity, CKMB mass, and total CK activity) performed because of hospitalization, i.e., coronary bypass and other surgical operations and coronary angiography performed for 47 (11.3%) patients with abnormal CKMB and CK levels. In seven cases, increases in CKMM related to various muscular diseases (muscular dystrophy or sclerodermatomyositis) were determined by usingthe clinical appearance of the patients. Among patients with muscular pathology, CK and CKMB activity results were found to be false positively increased after surgery and the CKMB: CK ratio was <5%. Through the evaluation of false-positive CKMB levels for 99 (3.0%) patients without AMI, MCK and high CKBB levels were found for 26 of them and a CKMB index of >25% was detected for all of them except for one patient with MCK-II, who was found to have <25% (Fig. 2).

TABLE I

LABORATORY RESULTS AND CLINICAL DIAGNOSES FOR PATIENTS WITH MCK- I, MCK-II, AND HIGH CKBB LEVELS

The CKMB index was found to be <5% for 48 (88.8%) of 54 patients who had undergone a surgical operation and for all patients with muscular pathology. That is, the CKMB index was determined to be <5% or >25% for 84 (75.6%) of 111 patients with abnormal CK and CKMB activity. In the present study, CKMB mass assays were normal for patients with MCK and increased CKBB values. CKMB mass values were found to be increased for two patients with AMI (Fig. 2).

Sensitivity, specificity, and predictive values were calculated using the results for 3,290 patients with or without MI. The CKMB mass was evaluated as being more sensitive and specific than any other markers in the first 24 hours after the appearance of symptoms. However, the low specificity of the CKMB assay was found to be increased with the use of the CKMB index and became closer to that of the CKMB mass (Table II).

Fig. 2. Comparison of CKMB levels and CKMB index values for all patients.

Discussion

Although various incidence studies of MCK-I, MCK-II, and high CKBB have been reported, clinical conditions and the mechanisms related to MCK have not yet been highlighted.8,15,16 MCK-I is formed particularly by the combination of CKBB and the light chain of monoclonal IgG. Although this reaction is based on an antigen- antibody interaction, this is not related to CKBB abnormalities. A similar interaction can occur between CKMM and IgA.7,17 No specific etiology was shown for the existence of MCK-I, but it is commonly found among both healthy people and patients with autoimmune diseases (particularly ulcerative colitis), cardiovascular diseases, and gastrointestinal diseases.8,9,16-19 MCK-I electrophoretically lies between CKMM and CKMB and is also called anodal MCK.

TABLE II

SPECIFICITY, SENSITIVITY, POSITIVE PREDICTIVE VALUE, AND NEGATIVE PREDICTIVE VALUE FOR ALL SUBJECTS

MCK-I has been reported to be determined with incidences of 0.61% and 0.53% in randomly selected groups, 0.23% in blood donor groups, and up to 6% among hospitalized patients.7,19,20 MCK-I is commonly seen in pathological conditions including intestinal adenoma, various types of carcinomas, myocardial injury, and other cases with the prognosis of high mortality rates. MCK-II is also known as mitochondrial CK or cathodal CK, which has high energy activity and enzyme kinetics.21 It has been suggested that MCK-II might be associated with end-stage malignancies and hepatic failure (particularly cirrhosis). The incidence of MCK-II was found to be 0.5 to 2.6% and 0.4 to 1.2% among hospitalized patients and in population screening, respectively.9,10,21-23 It was reported that MCK prominently interferes with measurement methods using immunoinhibition or an ion-exchange reaction.9,11,12 In this study, although no pathology was observed in 9 of 27 cases with MCK, the incidence of MCK (0.7%) in cases with suspected MI was rather close to the value found in the normal population.

In our study, CK levels were found to be increased in 4 of 10 MCK- I cases and 1 of 11 MCK-II cases. In a wide population study, Lee et al.9 found that total CK activities were increased in 60% of MCK-I cases and were within normal ranges in 75% of MCK-II cases.

Sensitivity and specificity values of CK and CKMB assays were found to be correlated with results of similar studies.1-3,13 According to the CKMB and CK results, low positive predictive values might be the reason for the large number of false-positive cases, because of patients who applied to the coronary emergency service with clinical MI suspicion or were then hospitalized. Therefore, the number of increased CKMB results could be prominently lowered by using CKMB mass, CKMB index, and repetitive measurements.

In this study, it was found that the increased number of cases with false high CKMB levels or CKMB index might be attributable to MCK and CKBB in given cases. In addition, CKMB mass values were determined to be within the normal range by using the chemiluminescence method in all cases with MCK and increased CKBB. This condition was evaluated with such great care that the ineffectiveness of MCK and CKBB increases found with the chemiluminescence measurement of CKMB mass might be assessed in cases with undifferentiated pathologies. Similarly, some authors reported that CKBB and MCK had no or little effect on CKMB analysis with a chemiluminometric analyzer.24-26

Although previous studies emphasized that MCK-I interfered with CKMB measurements using the immunoinhibition method, this study indicated that MCK-I, MCK-II, and CKBB increases caused false increases of CKMB and a false CKMB:CK ratio.19,27-33 In normal healthy populations, MCK and increased CKBB have a very low incidence; however, the incidence was greater (5.35%) among 448 cases with abnormal clinical and laboratory findings.

For practical and financial reasons, many clinical laboratories in Turkey and some other countries still use CKMB activity assays for biochemical diagnosis of AMI.34 As shown in this study, the method has obvious limitations for the detection or exclusion of AMI.

Consequently, it can be reported that, among patients diagnosed with an AMI who applied to the emergency service, no MCK and CKBB increase was detected with a higher incidence than that found in the normal population. It can also be suggested that MCK-I, MCK-II, and increased CKBB be taken into consideration in particular cases with normal ECG findings, high CKMB levels, and changes in the CK-MB:CK ratio. Moreover, CKMB mass determination may decrease the time spent for an accurate diagnosis.

References

1. Joint International Society and Federation of Cardiology/ World Health Organization Task Force on Standardization of Clinical Nomenclature: Nomenclature and criteria for diagnosis of ischmie heart disease. Circulation 1979; 59: 607-9.

2. Loti JA, Stang JM: Serum enzymes and isoenzymes in the diagnosis and differential diagnosis of myocardial ischemia and necrosis. Clin Chem 1980; 26: 1241-50.

3. Christenson RH, Azzazy HME: Biochemical markers of the acute coronary syndromes. Clin Chem 1998; 44: 1855-64.

4. Roxin LE, Cullhed I. Groth T, Halgren T, Venge P: The value of serum myoglobin determination in early diagnosis of acute myocardial infarction. Acta Med Scand 1984; 215: 417-25.

5. Gibler WB, Gibler CD, Weinshenker E: Myoglobin as an early indicator of acute myocardial infarction. Ann Emerg Med 1987; 16: 851-6.

6. Ohman EM, Casey C, Bengston JR, Pryor D, Tormey W, Horgan JH: Early detection of acute myocardial infarction: additional diagnostic information from serum concentrations of myoglobin in patients without ST elevation. Br Heart J 1990; 63: 335-8.

7. Apple FS, Henderson AR: Cardiac function. In: Tietz Textbook of Clinical Chemistry, Chapt 34, pp 1178-1203. Edited by Burtis CA, Ashwood ER. Philadelphia, PA, WB Saunders, 1999.

8. Moss DW, Henderson AR: Clinical enzymology. In: Tietz Textbook of Clinical Chemistry, Chapt 22, pp 657-65. Edited by Burtis CA, Ashwood ER. Philadelphia, PA, WB Saunders, 1999.

9. Lee KN, Csako G, Bernhardt P, Elin RJ: Relevance of macro creatine kinase type 1 and type 2 isoenzymes to laboratory and clinical data. Clin Chem 1994; 40: 1278-83.

10. Sturk A. Sanders GTB: Macro enzymes: prevalence, composition, detection and clinical relevance. J Clin Chem Clin Biochem 1990; 28: 65-81.

11. Loshon CA, McComb RB, Bowers GN Jr: lmmunoprecipitation and electrophoresis used to demonstrate and evaluate interference by CK- BB and atypical-CK's with CK-MB determinations by imrnunoinhibition. Clin Chem 1984; 30: 167-8.

12. Obzansky D, Lett JA: Clinical evaluation of an imrnunoinhibition procedure for creatine kinase MB. Clin Chem 1980; 26: 150-2.

13. World Health Organization: WHO Criteria for the Diagnosis of Acute Myocardial Infarction: Proposal for the Multinational Monitoring of Trends and Determinants of Cardiovascular Disease. Geneva, Switzerland, World Health Organization, 1981.

14. Devine JE, Wiens RD, Halstead JM, Codd JE: Quantitation of CK- MB release: diagnostic utility in coronary artery bypass grafting. Clin Chim Acta 1986; 156: 145-9.

15. Mifflin TE, Bruns DE: University of Virginia case Conference: macroamylase, macro creatine kinase, and other macroenzymes. Clin Chem 1985; 31: 1743-8.

16. Remaley AT, Wilding P: Macroenzymes: biochemical characterization, clinical significance and laboratory detection. Clin Chem 1989; 35: 2261-70.

17. Venta R, Geijo SA, Sanchez AC, et al: IgA-CKBB complex with CKMB electrophoretic mobility can lead to erroneous diagnosis of acute myocardial infarction. Clin Chem 1989; 35: 2003-8.

18. Whelan PV, Malkus H: A macro creatine kinase isoenzyme in serum of apparently healthy individuals. Clin Chem 1983; 29: 1411- 4.

19. TozawaT: Enzyme-linked immunoglobulins and their clinical significance. Electrophoresis 1989; 10: 640-4.

20. Laureys M, Sion J-P, Slabbynck H, et al: Macromolecular creatine kinase type 1: a serum marker associated with disease. Clin Chem 1991; 37: 430-4.

21. Rogalsky VY, Koven IH, Miller DR, Pollard A: Electrophoretic characteristics of macro creatine kinase type 2 in serum. Clin Chem 1986; 32: 13-5.

22. Wu AHB, Herson VC, Bowers GN Jr: Macro creatine kinase types 1 and 2: clinical significance in neonates and children as compared with adults. Clin Chem 1983; 29: 201-4.

23. Urdal P, Landaas S: Macro creatine kinase BB in serum, and some data on its prevale\nce. Clin Chem 1979; 25: 461-5.

24. Piran U, Kohn DW, Uretsky LS, et al: Immunochemiluminometric assay of creatine kinase MB with a monoclonal antibody to the MB isoenzyme. Clin Chem 1987; 33: 1517-20.

25. Delanghe JR, De Mol AM, De Buyzere ML, De Scheerder IK, Wieme RJ: Mass concentration and activity concentration of creatine kinase isoenzyme MB compared in serum after acute myocardial infarction. Clin Chem 1990; 36: 149-53.

26. Poirey S, Polge A, Bertinchant JP, et al: CKMB mass test in ischemic myocardial injury: comparison of two tests: Biomerieux Vidas and Sanofl access immunoassays. J Clin Lab Med 2000; 14: 43- 7.

27. Mederios LJ, Walsh D, Gerson B: Interference by macro creatine kinase type-1 with an immunoenzymometric method for quantification of CKMB in serum [letter]. Clin Chem 1986; 32: 710- 1.

28. Huggon AM, Chambers J, Nayem N, Tutt P, Crook M, Swaminathan S: Biochemical markers in the management of suspected acute myocardial infarction in the emergency department. Emerg Med J 2001; 18: 15-9.

29. Girgenti AJ, Brown MT, Arroyo JG: Interference with the determination of serum myocardial creatine kinase (CK-MB) by macro creatine kinase activity. Clin Chem 1980; 26: 977-8.

30. Devine JE: Macro-creatine kinase as interference in CK isoenzyme determinations. Enzyme 1983; 30: 139-44.

31. Strom S, Bendz R: Serum creatine kinase (CK) activity after M subunit inhibition in patients with atypical CK isoenzymes: a comparison to findings in acute myocardial infarction. Clin Chim Acta 1983; 132: 73-81.

32. Gorus F, Claessens V, Goubert P, Laureys MA: Sensitive bioluminescent immunoinhibition test for CK-B subunit activity and a CK-MB specific enzyme-linked immunosorbent assay compared: correlation with agarose electrophoresis and influence of CK- isoenzyme profile on results. Clin Chem 1988; 34: 1474-8.

33. Stein W, Bohner J: Influence of autoantibodies to creatine kinase-BB on assays for MB isoenzyme. Clin Chem 1985; 31:1189-92.

34. Hulting J, Waldenlind L, Onica D, Wallinder H: Creatine kinase-MB mass concentration versus creatine kinase-B activity for the detection of acute myocardial infarction in patients with slightly elevated total creatine kinase activity in serum. J Intern Med 1994; 235: 211-6.

Guarantor: Capt Trker Kutluay, Navy

Contributors: Commander Muhittin A. Serdar, Navy*; Lt Col Serhat Tokgoz[dagger]; Capt Grkan Metinyurt*; Capt Serkan Tapan*; Maj Krsat Erin[double dagger];; Lt Col Adnan Hasimi*; Maj Levent Kenar*; Col Cumhur BilgI[dagger]; Capt Trker Kutluay, Navy*

* Department of Clinical Chemistry, Glhane Military Medical Academy, Ankara, Turkey.

[dagger] Biochemistry Laboratory, Emergency Department, Glhane Military Medical Academy, Ankara, Turkey.

[double dagger] Department of Cardiology, Glhane Military Medical Academy, Ankara, Turkey.

This manuscript was received for review in March 2003. The revised manuscript was accepted for publication in August 2003.

Reprint & Copyright by Association of Military Surgeons of U.S., 2005.

Copyright Association of Military Surgeons of the United States Aug 2005

Source: Military Medicine

More News in this Category