At what level of serum total creatine kinase activity can measurement of serum creatine kinase MB isoenzyme activity be omitted in suspected myocardial infarction?

The purpose of this study was to establish a discriminatory limit for serum total creatine kinase activity (CK activity) below which CK isoenzyme fractionation is unnecessary. We looked at 2610 serum samples from 1077 consecutive patients with suspected acute myocardial infraction (AMI). The CK activity was determined according to the Scandinavian recommended method. Isoenzymes of CK were separated by agarose gel electrophoresis, followed by fluorometric scanning. When the threshold for CK activity was 150 U/l, none of the samples had a creatine kinase MB isoenzyme activity (CK-MB activity) equal to or higher than 30 U/l (the diagnostic level), which has been found to differentiate between patients with AMI and those without AMI. Only 14 patients (1.3% of all patients investigated) had CK-MB activity peaks between 10 U/l (detection limit) and 30 U/l. Of these, AMI was only diagnosed in one. We recommend that CK-MB activity should be measured only when CK activity is higher than 150 U/l. This would make about 50% of all CK-MB measurements unnecessary.     

Analytical and clinical evaluation of creatine kinase MB mass assay by IMx: comparison with MB isoenzyme activity and serum myoglobin for early diagnosis of myocardial infarction.

We analytically and clinically evaluated Abbott's IMx assay for creatine kinase (CK) isoenzyme MB (CK-MB) in serum. Over a 1-year period, the method was more specific but less precise than catalytic isoenzyme measurements by electrophoresis or immunoinhibition. Sera from different individuals without electrophoretic evidence of CK-MB but containing macro CK type 1 (n = 20), mitochondrial CK (n = 5), or CK-BB (n = 5) were scored as CK-MB negative by the IMx. Likewise, CK-MB-negative by the sera remained so after addition of purified human CK-MM (< or = 7600 U/L) or CK-BB (< or = 8100 U/L). For 39 patients admitted for suspicion of uncomplicated acute myocardial infarction (precordial pain for < or = 4 h), the diagnostic performance of the IMx CK-MB assay on admission and 4 h later was superior to that of total CK activity and compared well with that of CK-MB activity measured by electrophoresis or immunoinhibition. An admission, myoglobin showed a higher diagnostic sensitivity, specificity, and predictive value than did CK-MB and was the most informative test. Diagnostic performance on admission and 4 h later was further improved by considering positivity for myoglobin and for CK-MB by IMx and for the change in each over the first 4 h of hospitalization as criteria. Twelve hours after admission, diagnostic performance was further improved for all CK and CK-MB methods but began to decline for myoglobin.     

Serum CK-MB isoenzyme after aortic and mitral valve replacements

A release of the MB fraction of creatine kinase (CK) enzyme into the serum due to myocardial manipulation and trauma occurs in patients undergoing cardiac surgery. Thus, the appearance of CK-MB activity as such is not sufficient to indicate of perioperative myocardial infarction. The mean (+/- SD) serum CK-MB isoenzyme level was 95 +/- 103 U/l 18 hours after aortic or mitral valve replacement in 76 patients. Thirteen patients undergoing closure of an atrial septal defect served as controls. They had a significantly lower (p less than 0.01) isoenzyme level postoperatively: 45 +/- 39 U/l. Two patients had the ECG changes of definite myocardial infarction after valve replacement and they also showed high CK-MB values, while the other patients with high enzyme level had no ECG signs suggesting acute infarction. CK-MB values correlated with the aortic cross-clamping time (r = 0.39, p less than 0.001) and weakly with the precordial ECG voltage of SV1 + RV5 (r = 0.25, p less than 0.01). While these findings may reflect the sensitivity of a thick myocardial wall to ischaemia during surgery, the postoperative recovery was not related to the serum CK-MB level.     

Creatine kinase isoenzyme MB assay by electrophoresis

A method for determination of the creatine kinase isoenzyme MB (CK-MB) is reported: separation of the isoenzymes was done by electrophoresis and the activity of the isoenzyme bands quantitated by scanning fluorometry. Total CK activity was used for calculation of CK-MB level. The precision of the method was satisfactory: coefficient of variation 5-10%. Its accuracy good: CK-MB was consistently found in high concentrations in tissue extracts of myocardium, but was virtually absent in skeletal muscle and could not be demonstrated in serum from patients with skeletal muscle damage. The sensitivity of the method fitted its clinical use: CK-MB was undetectable (less than 5 U/l) in normal sera, below 30 U/l in seventy-six out of seventy-seven patients in whom the diagnosis of acute myocardial infarction (AMI) was disproved, and above 30 U/l in all seventy-two patients with AMI according to WHO criteria. The CK-MB concentration in serum rises to a maximum about 20 h after onset of clinical symptoms of AMI and reaches baseline levels 20-30 h later. The electrophoretic CK-MB method is easy, fast and reliable and is considered as an important diagnostic test for AMI.     

IgA-CK-BB complex with CK-MB electrophoretic mobility can lead to erroneous diagnosis of acute myocardial infarction

This patient, on admission, presented with a tentative diagnosis of myocardial infarction: the electrocardiogram showed a nonspecific ST-segment and T-wave abnormalities, and total creatine kinase (CK; EC 2.7.3.2) activity was slightly increased (238 U/L). However, a high electrophoretic value for CK-MB (50% of total CK activity) and the electrophoretic pattern of lactate dehydrogenase (EC 1.1.1.27) isoenzymes ruled out myocardial infarction. The isoenzyme migrating as CK-MB was found later to contain no immunologically normal CK-M subunits, and it was bound to IgA. A mixture of the patient's serum and a human serum control containing all CK isoenzymes showed altered electrophoretic mobility only for CK-BB, indicating that the patient's serum contained antibodies to the B unit of CK. Elution from a Sephadex G-200 column showed that the peak at which most of the anodic CK was eluted corresponded to a molecular mass of approximately 200 kDa. Evidently this atypical isoenzyme was an IgA-CK-BB complex. Because this macro CK type 1 can mimic CK-MB, it may therefore be a source of confusion.     

Differentiating muscle damage from myocardial injury by means of the serum creatine kinase (CK) isoenzyme MB mass measurement/total CK activity ratio

We immunoenzymometrically measured creatine kinase (CK) isoenzyme MB in extracts of myocardium and in homogenates of five different skeletal muscles. CK-MB concentrations in the former averaged 80.9 micrograms/g wet tissue; in the skeletal muscles it varied widely, being (e.g.) 25-fold greater in diaphragm than in psoas. CK-MB in skeletal muscles ranged from 0.9 to 44 ng/U of total CK; the mean for myocardium was 202 ng/U. In sera from 10 trauma and 36 burn patients without myocardial involvement, maximum ratios for CK-MB mass/total CK activity averaged 7 (SEM 1) ng/U and 18 (SEM 6) ng/U, respectively. Except for an infant (220 ng/U), the highest ratio we found for serum after muscular damage was 38 ng/U. In contrast, the mean maximum ratio determined in 23 cases of acute myocardial infarction exceeded 200 ng/U. Among seven determinations performed 8 to 32 h after onset of symptoms, each infarct patient demonstrated at least one ratio greater than or equal to 110 ng/U. Ratios observed after infarct were unrelated to treatment received during the acute phase. We propose a CK-MB/total CK ratio of 80 ng/U as the cutoff value for differentiating myocardial necrosis from muscular injury.     

Immunoenzymetric assay for creatine kinase MB with subunit-specific monoclonal antibodies compared with an immunochemical method and electrophoresis

Results of an immunoenzymetric assay (TANDEM-E CKMB) for creatine kinase (CK; EC 2.7.3.2) MB isoenzyme, in which subunit-specific monoclonal antibodies are used, were compared with those by an immunochemical method (Isomune-CK) and electrophoresis (Corning agarose gel). The study involved 200 patients; greater than 500 samples were analyzed by all three methods. The analytical performances were acceptable. Between-method correlation coefficients ranged from 0.881 to 0.975. Two reference intervals were established for the immunoassays: 0-4 micrograms/L (TANDEM) and 0-4 U/L (Isomune) for "normal" patients; 0-9 micrograms/L (TANDEM) and 0-14 U/L (Isomune) for noninfarct patients. Agreement with respect to increased CK-MB as defined by the reference intervals for the noninfarct patient was 96% between TANDEM and electrophoresis, 90% between Isomune and electrophoresis. All three methods are acceptable for use in determining CK-MB, but the overall diagnostic efficiencies for the mass or activity concentration of the isoenzyme and for its proportion of total CK activity, based on the predictive value model, are 92% (electrophoresis, 0-7 U/L), 90% (electrophoresis, 0-4%), 92% (TANDEM, 0-9 micrograms/L), 88% (TANDEM, 0-3% index), 88% (Isomune, 0-14 U/L), and 83% (Isomune, 0-4%). All three methods can detect CK-MB in serum, but its presence is not necessarily diagnostic of acute infarct. We recommend using the actual concentration of CK-MB to evaluate patients with suspected acute myocardial infarct, and the percentage of CK-MB when total CK is very high.     

肌酸激酶同工酶质量判定肌病心肌损害的局限性

目的 通过对比小儿心肌炎、肌病时血清中肌酸激酶同工酶(CK-MB)质量与肌钙蛋白I(cTnI)和肌红蛋白(Mb)的动态变化,观察CK-MB质量在判定心肌损伤中的意义.方法 测定40例心肌炎患儿(其中有20例为暴发性心肌炎)和38例肌病患儿的肌酸激酶(CK)、CK-MB活性、CK-MB质量、cTnI、Mb、心电图以及脉冲多普勒超声心动图;肌病组同时进行肌电图、遗传代谢病筛查以及基因检测.以同期本院发育儿科门诊除外甲状腺功能减低症的10例身矮待查儿童为对照.结果 ①健康对照组儿童CK(U/L)为95.0±27.0,CK-MB活性(U/L)为22.6±1.3,CK-MB质量(μg/L)为2.4±0.3,cTnI(μg/L)为0.012±0.001.②心肌炎组患儿治疗前CK(1 033.0±408.0)、CK-MB活性(101.2±31.5)、CK-MB质量(38.2±13.2)、cTnI(5.544±1.554)均较健康对照组明显升高(均P＜0.01);随着治疗时间延长,各项指标逐渐下降;治疗2周后CK(59.3±25.1)、CK-MB活性(24.6±13.2)、CK-MB质量(3.3±2.9)、cTnI(0.125±0.128)均恢复至正常水平(均P＞0.05).治疗1周后CK、CK-MB质量增高率即较治疗前明显下降[CK:5.9％(1/17)比56.4％(22/39);CK-MB质量:8.3％(1/12)比61.1％(22/36),均P＜0.01],CK-MB质量恢复先于cTnI,增高率出现明显差异[8.3％(1/12)比73.7％(14/19),P＜0.05].③肌病组治疗前CK(10 193.0±1 447.0)、CK-MB活性(311.7±44.4)以及CK-MB质量(229.2±47.9)均较健康对照组明显升高(均P＜0.01),但cTnI不高(0.021±0.002);治疗2周后CK(5 735.6±6 187.8)、CK-MB活性(170.7±143.0)、CK-MB质量(207.4±136.6)仍维持在高水平,cTnI(0.230±0.150)则维持在正常水平;各项指标的增高率与治疗前均无显著差异[CK:85.7％(6/7)比97.4％(37/38); CK-MB活性:85.7％(6/7)比97.4％(37/38);CK-MB质量:100.0％(2/2)比94.1％(32/34);cTnI:0(0/1)比6.4％(2/31),均P＞0.05].结论 ①在心肌炎时,CK-MB质量与cTnI一致,急性期升高,恢复期降至正常,但CK-MB质量观察窗短于cTnI.②在肌病时,CK-MB质量与cTnI 分离,前者治疗前后均升高,后者正常,故用测定CK-MB质量来判定肌病患儿是否有心肌损害意义有限.     

Cardiospecificity of the 3<Superscript>rd</Superscript> generation cardiac troponin T assay during and after a 216 km ultra-endurance marathon run in Death Valley

Background The reasons for the appearance of cardiacspecific troponin (cTnT) after strenuous exercise are unclear. The aim of the present study was to evaluate the cardiospecificity of the 3^rd generation cardiac cTnT assay during and after an ultra-endurance race of 216 km at extreme environmental conditions in Death Valley. Study design and methods We measured serially cTnT, creatine kinase (CK), activity and mass of the isoenzyme MB of CK (CK-MB_act and CK-MB_mass), and myoglobin in 10 well-trained athletes before, repeatedly during and after the race. Results Six of 10 participants finished the race within a preset time of 60 hours. Postrace values of biochemical markers CK, CK-MB_act, CKMB_mass, and myoglobin were significantly increased compared to baseline (p<0.05). CK-MB_act increased from (median (25^th/ 75^thpercentile) 12 (10/13) U/L to 72 (32/110) U/L, CK-MB_mass from 3.9 (2.9/5.6) U/L to 65 (18/80) U/L and CK increased from median 136 (98/ 228) U/L to 3,570 (985/6,884) U/L respectively. Pre-race myoglobin was 27 (22/31) μg/l compared to 530 (178/657) μg/l after the run. One runner developed significant exercise-induced rhabdomyolysis with spontaneous recovery. cTnT values remained below the 99^th percentile reference limit in all athletes including the runner who developed significant rhabdomyolysis (peak CK 27,951 U/L). Conclusions Strenuous endurance exercise, even under extreme environmental conditions, does not result in structural myocardial damage in well-trained ultra-endurance athletes. We found no crossreactivity between cTnT and CK, neither in exercise-induced skeletal muscle trauma nor after rhabdomyolysis underscoring the excellent analytical performance of 3^rd generation cTnT assay.     

Semi-automated direct colorimetric measurement of creatine kinase isoenzyme MB activity after extraction from serum by use of a CK-MB-specific monoclonal antibody

This semi-automated colorimetric assay for the MB isoenzyme of creatine kinase (EC 2.7.3.2) is based on a monoclonal antibody ("Conan-MB") specific for this isoenzyme and is a modification of a previously published method (Vaidya et al., Clin Chem 1986;32:657-63). A 0.64-cm bead coated with 2 to 3 micrograms of antibody is incubated with 100 microL of serum and 10 microL of 0.2 mol/L beta-mercaptoethanol for 1 h at room temperature, to extract CK-MB. The beads are washed with de-ionized water and incubated with CK substrate for 45 min at 37 degrees C. A solution containing trans-1,2-diaminocyclohexane-N,N,N', N'-tetraacetic acid, p-iodonitrotetrazolium violet, and diaphorase is added and the resulting colored product is measured at 492 nm. The standard curve is linear to 200 U of CK-MB per liter, and analytical recovery is 97-113%. Total assay CV for low (9.7 U/L) and high (50.7 U/L) quality-control materials was 14.1% (n = 1878) and 11.6% (n = 1842), respectively. CK-MB activity correlated well (r = 0.978, n = 226) with CK-MB measured by a two-site mass immunoassay, and 99.4% of samples with CK-MB greater than or equal to 12 U/L (n = 347) were verified by electrophoresis on agarose.     

Early elevation of S-100B protein in blood after cardiac surgery is not a predictor of ischemic cerebral injury

BACKGROUND: We hypothesized that early changes in S-100B levels after cardiac surgery are nonspecific and mostly reflect damage to tissues outside the brain rather than ischemic brain damage. METHODS: We measured serum levels of S-100B at several times perioperatively in 21 patients undergoing cardiac surgery. In addition, we measured levels of neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), creatine kinase (CK), the cardiac isoenzyme of CK (CK-MB), and myoglobin (MB) in these patients. RESULTS: Early increases in serum S-100B concentration were significantly (p<0.01) correlated with increases in markers of tissue injury outside the brain: S-100B/CK: r(2)=0.69; S-100B/CK-MB: r(2)=0.64; S-100B/myoglobin: r(2)=0.60; S-100B/NSE: r(2)=0.51; CK/NSE: r(2)=0.60; CK-MB/NSE: r(2)=0.59; and myoglobin/NSE: r(2)=0.54. CONCLUSIONS: Our findings indicate that increases in S-100B in the early phase after cardiac surgery are not due to release of S-100B from brain alone but also from tissue outside the brain.     

手足口病患儿联合检测肌酸激酶同工酶MB、心肌肌钙蛋白Ⅰ在合并病毒性心肌炎诊断中的价值

目的探讨手足口病患儿联合检测血清中肌酸激酶同工酶MB（CK—MB）、心肌肌钙蛋白Ⅰ（cTnI）水平对诊断合并病毒性心肌炎的价值。方法将188倒HFMD患儿分为确诊合并精毒性心肌炎组、疑似舍并病毒性心肌炎组、无合并病毒性心肌灸组。所有惠儿清晨空腹采集静脉血,检测血清中的肌酸激酶同工酶MB（CK—MB）、心肌肌钙蛋白Ⅰ（cTnI）水平,对结果进行统计分析。结果确诊合并病毒性心肌炎组与疑似合并病毒性心肌炎组血清中CK—MB、cTnI均高于无合并病毒性心肌炎组,差异有统计学意义（P〈0．05）;确诊合并病毒性心肌炎组血清中CK—MB、cTnI与疑似合并病毒性心肌炎组比较差异无统计学意义（P〉0．05）。确诊组与疑似组两项检测中的总异常率均分别高于两纽中CK—MB、cTnI单独检测异常率（P〈0．05,P〈0．05）。结论CK—MB、cTnI在HFMD中诊断合并病毒性心肌炎有重要意义;HFMD患儿同时检测血清中CK—MB、cTrI水平,可以提高合并病毒性心肌炎的捡出率。     

A sensitive bioluminescent immunoinhibition test for CK-B subunit activity and a CK-MB specific ELISA compared: correlation with agarose electrophoresis and influence of CK-isoenzyme profile on results

Searching for alternatives to the imprecise spectrophotometric tests for low-concentration creatine kinase (EC 2.7.3.2) isoenzyme MB (CK-MB), we investigated the analytical performance of two potentially superior approaches--a bioluminescent immunoinhibition assay (I, LKB-Wallac) and an ELISA (enzyme-labeled immunosorbent assay) technique (II, Hybritech)--in comparison with an electrophoretic method (III, Beckman). Only I showed good between-day precision (CV 8.3%) at the upper reference limit, allowing reproducible assay of CK-B subunit activity down to at least 3 U/L. In conditions where CK isoenzyme assays remained unaffected by CK-MM concentrations, test results were proportional to the amount of CK-MB in the sample up to at least 50 U/L for I, 120 micrograms/L for II, and 100 U/L for III (r greater than 0.998 by linear regression analysis). For CK-MB-positive samples, the data by I correlated more closely with values by III (n = 24; r = 0.994) than did results by II (n = 15; r = 0.909), but both methods were equally effective in discriminating between samples with or without electrophoretically supranormal CK-MB activity (93% sensitivity). II was entirely CK-MB specific, whereas CK-B activity by I was consistently (18/18) increased in CK-MB-negative samples containing CK-BB (n = 6; r = 0.996) or macro CK, types 1 or 2 (n = 12; r = 0.930). I is highly sensitive for screening for increased non-MM CK activity, the nature of which should be subsequently clarified by electrophoresis.     

Clinical effectiveness of the Du Pont aca measurement of creatine kinase MB in serum from patients in a coronary-care unit

We evaluated the clinical effectiveness of measuring creatine kinase (CK; EC 2.7.3.2) isoenzyme MB and lactate dehydrogenase (LD; EC 1.1.1.27) isoenzymes in diagnosis of acute myocardial infarction. We used an agarose electrophoresis method to measure CK and LD isoenzymes and the Du Pont aca column method to measure CK-MB. Serial blood specimens were drawn from 100 patients consecutively admitted to our Coronary Care Unit. Because of the low diagnostic specificity for CK-MB measurements by both agarose electrophoresis and the discrete-analysis method, as compared with reported values, we re-evaluated our isoenzyme data by using Receiver Operating Characteristic curves. Such analysis of the data established optimal decision levels of greater than or equal to 25 U/L and greater than or equal to 18 U/L plus greater than or equal to 6% of total CK for serum CK-MB measured by the agarose electrophoresis and the aca methods, respectively, and an optimal decision level of greater than or equal to 0.92 for the ratio of LD 1/2 measured after agarose electrophoresis. At these decision levels we obtained a sensitivity of 100%, 100%, and 95% and a specificity of 94%, 92%, and 90% for CK-MB (agarose electrophoresis), CK-MB (aca), and the LD 1/2 ratio, respectively.     

Preparation and stability of a liquid creatine kinase isoenzyme control from rabbit serum.

The MB isoenzyme of creatine kinase (CK) may be prepared in vitro from rabbit serum containing only the MM and BB isoenzymes, by means of a hybridization technique. The MM and BB dimers dissociate in 4 mol/L urea, which allows random recombination of M and B monomers. A liquid CK-isoenzyme control can be made from mixtures of rabbit sera obtained after hybridization and stabilized with glycerol and 25 mmol of 2-mercaptoethanol per liter. A liquid control stored at 4 degrees C showed good stability over a three-month period, declining to a mean residual activity of CK of approximately 90% after three weeks and a mean residual activity of MM, MB, and BB of 80--85% after six weeks. At 25 degrees C, CK activity of the liquid control declined to 75--80% after the fourth week. CK-BB at 25 degrees C was the least stable isoenzyme, declining to 75% after the third week and reaching 60% of activity after 12 weeks. CK-MB and CK-MM showed approximately 10--15% less stability at 25 degrees C than at 4 degrees C.     

Mass concentration and activity concentration of creatine kinase isoenzyme MB compared in serum after acute myocardial infarction

We compared three current methods (immunoinhibition, "Isomune-CK" immunoprecipitation, and the Tandem-E CKMB II immunoenzymometric assay) for determination of creatine kinase (CK; EC 2.7.3.2) isoenzyme MB in serum. Although results inter-correlated well, the immunoinhibition assay gave higher activity values. Atypical CK forms did not interfere with the immunoprecipitation and immunoenzymometric methods. In acute myocardial infarction the catalytic properties of CK decreased with the enzyme's age, as reflected by a steady increase in activation energy of the catalyzed reaction. In septicemia patients with very low CK and CK-MB catalytic activity, mean CK-MB mass concentration exceeded the upper reference limit, suggesting an increased rate of loss of activity concentration in these patients' sera. Because of the assay's lesser susceptibility to conformational changes at the active site of the enzyme, we suggest that measurement of CK-MB mass concentration is better suited for infarct sizing than measurement of catalytic activity.     

Creatinine-kinase-MB determination in non-cardiac trauma: its difference with cardiac infarction and its restricted use in trauma situations.

Cardiac injuries can be life threatening. The possibility of late complications urges the practitioner to search for any evidence of cardiac trauma. But the diagnosis of cardiac injury remains difficult. Electrocardiography and cardiac enzyme determination are most widely used, because they are readily available. Many studies advocate creatine-kinase-MB (CK-MB) isoenzyme levels as a sensitive test for cardiac contusion. Others have discarded CK-MB testing as useless in trauma situations. An elevated CK-MB value in haemodynamically stable patients may confuse the individual practitioner. To better clarify its role we investigated the course of CK/CK-MB release after trauma, with no or only a very small chance of cardiac injury and compared it with patients with severe chest trauma having cardiac complications. A total of 25 trauma patients with only skeletal muscle injury were studied. Blood samples were taken during the first 4 days after trauma. These results were compared with those of a group of 91 consecutive patients with severe chest injury, including 10 with cardiac complications. Initial results in skeletal trauma patients were indicative of cardiac injury (CK > 5% of total CK and at least 20 U/l) in 10 patients. These findings were identical to those found in patients with severe chest injury having cardiac complications. CK/CK-MB tests are frequently positive after trauma without cardiac injury, even when selective criteria are used. The time each isoenzyme is released from muscle tissue after trauma greatly influences the outcome of the test. As this release does not occur at the same moment for each isoenzyme, the test result is very much time-dependent. As a result of these findings CK-MB testing tends to cause more confusion than clarification in trauma situations. We therefore eliminated CK-MB testing from our trauma protocol as a screening investigation for cardiac injury.     

Sensitive, rapid assay of subforms of creatine kinase MB in plasma

The subforms of creatine kinase (CK; EC 2.7.3.2) in plasma have received recent attention as potential markers for the early diagnosis of acute myocardial infarction. Because changes in CK-MM subforms are not specific for myocardial injury, we developed an assay, based on high-voltage electrophoresis, that is sufficiently sensitive to detect the CK-MB subforms at concentrations substantially below the upper limit of normal (14 U/L). The assay can detect 1.25 U of either MB subform per liter with a precision of 0.20 U/L and gives responses that vary linearly with activity concentration from 0.0 through 30.0 U/L, with an identical signal response for both subforms. When both subforms are present in a serum sample, the assay accurately measures both the relative percentage and the absolute quantity of each: assay activity/known activity was 1.03 for each subform at a total MB subform activity of 5.0 U/L (r = 0.98). Assay time is 25 min, and there is no loss of CK during electrophoresis. Thus, this system can be used to rapidly, sensitively, and precisely quantify the two CK-MB subforms at activities well within the normal reference interval.     

Creatine kinase MB in cases of skeletal muscle trauma

Fifty-eight patients admitted through our emergency room with severe skeletal muscle injury but no obvious cardiac contusions were evaluated for creatine kinase isoenzyme MB (CK-MB). When such patients show an above-normal value for total CK, it is a question of whether or not myocardial injury has been sustained along with skeletal muscle injury when (a) there are no obvious chest contusions or (b) the patient is unconscious and unable to complain of chest pain. Whenever there is doubt concerning the cardiac status of a patient, lactate dehydrogenase (LD) isoenzymes, serial electrocardiograms, and CK isoenzymes are ordered. Our study revealed that serum of 8.6% of the trauma victims had CK-MB values exceeding 5.0 EU/L (reflecting abnormal CK-MB concentrations) as part of their increased total CK. All patients had normal electrocardiographic patterns along with negative results for LD isoenzymes; none had sustained any demonstrable myocardial injury. The CK-MB value must be interpreted together with the total CK value for appropriate diagnosis in patients with skeletal muscle trauma.     

Diagnosis of perioperative myocardial infarction by considering relationship of postoperative electrocardiogram changes and enzyme increases after coronary bypass operation

We report the results of enzyme determinations in sera from 88 patients, 65 of whom showed inconspicuous reconvalescence, 14 who had myocardial infarction within 24 h (MI 1) after bypass surgery, and nine with myocardial infarction between 24 and 48 h postoperatively (MI 2). We wanted to determine whether the consequent measurement of activities of total creatine kinase (CK), CK isoenzyme MB (CK-MB), lactate dehydrogenase, alpha-hydroxybutyrate dehydrogenase, and aspartate aminotransferase, conducted as a part of routine laboratory diagnostics, provided meaningful information for diagnosing infarcts besides that obtained from the electrocardiogram. The postoperative mean values of the enzyme activities in blood were significantly different among the three groups; however, only a combined evaluation of CK and CK-MB by means of a discriminant analysis allowed the prediction of MI (sensitivity: MI 1 = 98.5%, MI 2 = 95.4%; specificity: MI 1 = 71.4%, MI 2 = 81.8%). CK greater than 600 U/L or CK-MB greater than 45 U/L supports the diagnosis of acute MI.