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.     

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.     

Immunoenzymometric assay of creatine kinase with monoclonal antibodies to the MB isoenzyme compared with electrophoresis

We compare a "second-generation" immunoenzymometric assay (Tandem-E CKMB II) for creatine kinase (EC 2.7.3.2) MB with its electrophoretic (Beckman Paragon system) determination. In the former, two monoclonal antibodies are directed against the B and M subunits. We evaluated 502 samples from 253 patients. Precision, linearity, and analytical recovery for both assays were excellent. The two methods correlated well (r = 0.936). The reference interval for individuals with no suspected cardiac disorder was 0-6.0 micrograms/L; that for non-infarct patients was 0-18.0 micrograms/L. Peak CK-MB values determined by the two assays agreed for 95% of the patients, in terms of exceeding the normal reference interval or not. Diagnostic efficiencies were 86% (Tandem) and 88% (electrophoresis). The immunoenzymometric assay showed no cross reaction with other CK isoenzymes. Both assay methods performed well in detecting CK-MB, although there were some false positives by both methods, as judged from electrocardiographic results. When total CK for the Tandem assay exceeds 2000 U/L, we recommend calculation of a ratio (CK-MB, micrograms/L:total CK, U/L).     

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.     

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.     

Production of recombinant human creatine kinase (r-hCK) isozymes by tandem repeat expression of M and B genes and characterization of r-hCK-MB

BACKGROUND: Serum creatine kinase-MB isoenzyme (CK-MB) is widely used as a marker of myocardial injury. We prepared recombinant human CK (r-hCK) MB isoenzyme and examined its potential for use as a control material for assay of CK-MB in serum. METHODS: cDNAs encoding CK-M and CK-B subunits were inserted into the same plasmid vector, followed by transformation of Escherichia coli. The resulting three types of CK isoenzymes were purified by conventional chromatography. RESULTS: The ratio of MB to MM to BB was 50:40:10 on the basis of CK activity. Highly purified CK-MB with a specific activity of 533 U/mg was produced in a yield of 5.7 mg/g of packed cells. Purified r-hCK-MB had the isoelectric point (pI 5.3) and molecular size (46 kDa for the subunit) of native CK-MB. Its immunoreactivity in an ELISA using antibody against native heart enzyme was similar to that of cardiac CK-MB. The r-hCK-MB retained >90% activity for at least 4 months at 11 degrees C in a delipidated serum matrix in a liquid form at a concentration of 118 U/L. CONCLUSIONS: r-hCK-MB shows key properties of the native cardiac isoenzyme and may be useful as a control and calibrator for serum assays of CK-MB.     

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.     

Separation of CK isoenzymes on DEAE-sephadex A-50 at neutral pH

The MM, MB and BB isoenzymes of human creatine kinase (CK) were separated by elution from micro-columns of DEAE-Sephadex A-50 with Tris buffer containing increasing concentrations of NaCl at pH 7.0, instead of pH 8.0 as has commonly been used. Since pH 7.0 is close to the pH optimum of CK, this allowed the use of four times larger aliquots of the eluates for the estimation of CK activity and, consequently, a 4-fold increase in sensitivity. Using serum specimens from patients with acute myocardial infarction, there was a good correlation of the CK-MM (r = 0.99) and CK-MB (r = 0.93) activities obtained with the two buffer systems. Similarly, normal sera had CK-MB and CK-BB activities of less than 2 U/l with both buffer systems. Comparison of the composition of serum proteins in the eluates by conventional electrophoresis revealed that although the distribution of CK isoenzymes separated by the two buffer systems was similar, the distribution of proteins at pH 7.0 showed an appreciable shift of protein from the MB to the MM eluates.     

Clinical and analytical evaluation of two immunoassays for direct measurement of creatine kinase MB with monoclonal anti-CK-MB antibodies

We examined the clinical and analytical performance of two immunoassays (Becton Dickinson CK-MB; Ciba-Corning Magic Lite CK-MB) in which monoclonal anti-CK-MB antibodies are used for directly measuring creatine kinase (EC 2.7.3.2) isoenzyme MB (CK-MB) in serum, and also one electrophoretic method (Ciba-Corning). Within- and between-assay precision for both immunoassays was good at the upper reference limits (less than 10% CV). Analytical recoveries ranged from 102 to 114%. Both immunoassays were free from interference by CK-BB, mitochondrial-CK, macro-CK, adenylate kinase, and CK-MM. Retrospectively, we evaluated four categories of patients, using both immunoassays and electrophoresis: normal controls, acute myocardial infarction (AMI) patients, severe skeletal muscle trauma patients, and acutely ill patients known not to have AMI. In general, there were excellent correlations among all three methods. CK-MB activity (U/L) measured by the Becton Dickinson immunoassay was approximately 50% of the mass concentration (microgram/L) of the Magic Lite immunoassay and 50% of the activity concentration (U/L) determined by electrophoresis. Both immunoassays were easy to perform and sensitive to the low CK-MB concentrations often found with low total-CK activities.     

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.     

Changes in serum CK-MB mass after coronary artery bypass surgery

We assessed the release of creatine kinase MB as both mass and activity during the postoperative period following cardiac surgery. CK-MB mass was determined by enzyme immunoassay using reagents obtained from Hybritech. CK-MB activity was determined both by agarose electrophoresis and by an immunochemical method. Fifty-five patients who underwent coronary artery bypass surgery and 52 control subjects who had orthopedic surgery were selected for study. Serial serum samples were collected following surgery and total LD, CK, AST, LD-1, CK-MB mass, and CK-MB activity determined. Results were compared to each other and to surgical parameters. All patients exhibited significant CK-MB mass and activity after surgery and peak serum levels were 6-94 micrograms/L and 12-84 U/L, respectively. CK-MB mass correlated with CK-MB activity on paired samples (r = 0.94). Total AST and CK activities correlated with CK-MB mass (r = 0.60, and 0.63, respectively). Peak levels of CK-MB mass correlated significantly with peak MB activity (r = 0.88), peak LD-1 (r = 0.62), peak AST (r = 0.71), and time on pump (r = 0.54). Similar correlations were also seen between peak CK-MB activity and these parameters. No relationship could be identified between extent of CK-MB mass release and number of grafts, degree of hypothermia, or minimum PaO2. The time course of CK-MB mass release exhibited 85% concordance with CK-MB activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

Immunochemical extraction and automated measurement of plasma creatine kinase MB isoenzyme and creatine kinase MB2 isoform

Measurement of creatine kinase MB (CK-MB) and its isoforms CK-MB₂ and CK-MB₁ are now applied in the diagnosis of acute myocardial infarction (AMI). The most common approach for analysis includes RIA, IRMA, and electrophoresis, all of which may be time-consuming. This study examines determination of CK-MB and CK-MB₂ by a rapid immunochemical extraction method followed by an automated measurement for both analytes. The automated method was sensitive to 2 U/L, linear to 180 U/L, and gave excellent interassay precision (<10% CV). Interference studies indicated that bilirubin, hemolysis, and lipemia caused analytical problems as did the presence of high activities of other CK isoenzymes, notably CK-MM and CK-BB, requiring dilution of samples prior to analysis. Application of immunochemical extraction gave a reference interval of CK-MB (0–2.5 U/L) and CK-MB₂ (0.1–1.4 U/L) for blood donors (20–60 years), peak levels for ruled-out AMI patients of CK-MB (0.5–7.3 U/L) and CK-MB₂ (0.3–4.9), peak levels for ruled-in AMI patients of CK-MB (80–174 U/L) and CK-MB₂ (80–155 U/L). Coronary artery bypass patients (n = 24) and all trauma patients (n = 14) also demonstrated elevations in CK-MB and CK-MB₂, whereas only five of the trauma patients demonstrated increased CK-MB by IRMA. In patients (n = 7) having increased total CK and normal CK-MB by IRMA, the extraction assay for CK-MB and CK-MB₂ yielded increased values in all patients. This new approach to CK-MB and CK-MB₂ analysis can be performed within 30 minutes of sample receipt. J. Clin. Lab. Anal. 11:163–168, 1997. © 1997 Wiley-Liss. Inc.     

Activity concentration and mass concentration (monoclonal antibody immunoenzymometric method) compared for creatine kinase MB isoenzyme in serum

Results of the "Tandem-E CKMB" immunoenzymometric procedure (y) for creatine kinase (CK; EC 2.9.3.2) were compared with electrophoresis (x) for 160 serum samples from patients suspected of having sustained myocardial infarctions. The results correlated well: y, microgram/L (Tandem assay) = 1.3x-6.3 U/L(electrophoresis) (r = 0.95). CK-MB mass measurement was more stable than enzyme activity after storage and appeared to be more sensitive. Sera from 86 other people, which had no detectable CK-MB upon electrophoresis, gave a mean CK-MB value of 1.1 microgram/L (SD 1.3, range 0-8) with the Tandem assay. To determine whether these low values represented actual isoenzyme, we tested for possible interference by heterophile antibodies in the patients' sera by preincubating the samples with mouse serum before the Tandem assay. The mouse serum did not interfere with the assay of sera that had substantial quantities of CK-MB by electrophoresis. However, in five of six samples that were negative by electrophoresis, the CK-MB values were substantially smaller, indicating that the values measured were false-positives caused by the presence of heterophile antibodies directed against mouse proteins, an interference that could be eliminated by pretreatment with mouse serum.     

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.     

Creatine kinase isoenzymes in human cerebrospinal fluid and brain

Extracts of normal brains obtained at autopsy and cerebrospinal fluid (CSF) from patients with global brain ischemia were analyzed for creatine kinase (CK; EC 2.7.3.2) isoenzymes. We used both qualitative and quantitative assays (electrophoresis and immunoinhibition). Brain extracts contained CK-BB isoenzyme and mitochondrial CK. In 54 CSF samples free of blood contamination and with total activities ranging from 7 to 2010 U/L (mean 202 U/L), virtually all of the CK activity was due to CK-BB, and none to CK-MM or CK-MB. We conclude that brain contains CK-BB and mitochondrial CK, but lacks CK-MM and CK-MB. After cardiac arrest, CK-BB is released into the CSF. Any CK-MM in the CSF is probably from blood contamination, in which case immunoinhibition with anti-CK-M antibodies accurately quantifies CK-BB.     

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.     

Macro creatine kinase type 1 with electrophoretic mobility identical to that of the MB isoenzyme

We describe the case of an elderly woman whose symptoms and electrocardiographic pattern initially suggested acute myocardial infarction. The value for total serum creatine kinase (EC 2.7.3.2; CK) was 737 U/L (reference interval: 22-269 U/L), and electrophoresis for CK isoenzymes demonstrated two bands, the more anodal migrating to the CK-MB region and the second migrating between the CK-MB and CK-MM regions. The above-normal total CK and electrophoretic pattern persisted during her 11-day hospital course. The QuiCK-MB (International Immunoassay Labs.) and Tandem-E CK-MB (Hybritech) immunoassays, however, showed CK-MB mass measurements within the normal range. In further investigation with a mixture of patient's serum and human-serum-based control containing all CK isoenzymes, the electrophoretic mobility of only CK-BB was altered, proving that the patient had antibody to the B unit of CK in her serum. Immunofixation revealed the more anodal band to be a CK-IgA lambda complex, and the more cathodal band, a CK-IgG kappa complex. Mixing the patient's serum with polyclonal antibody specific for CK-B slowed the electrophoretic mobility of only the more anodal band. Polyclonal antibody specific for CK-M had no effect on either band. Evidently, this patient had two different types of macro CK type 1, both containing CK-BB. We conclude that macro CK type 1 can mimic CK-MB and be a source of confusion.     

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.