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.     

Creatine kinase isoenzymes in the diagnosis of acute cranio-cerebral trauma

The cerebrospinal fluid (CSF) creatine kinase (CK) activity and isozymic spectrum (EC 2.7.3.2) have been examined in patients with craniocerebral injuries of varying severity. The CK activity has been elevated in all the patients. Three isoforms have been detected: CK-BB, CK-MB, and CK-MM. CK-BB has been detected in all the patients in the presence of the total CK activity; this is explained by the isozyme release from the brain tissue during the injury and as a result of functional and structural impairment of the cellular membranes in intensification of lipid peroxidation. The CK-MM activity is due to blood admixture in the CSF and to impaired hematoencephalic barrier during the injury. The presence of CK-MB in the CSF of patients without cardiac symptoms probably results from a recombination of CK-BB and CK-MM isoforms and is of no diagnostic significance. Measurements of the total and isozymic CK activity in the CSF of patients with craniocerebral injuries may become a test for the laboratory diagnosis of the trauma severity and course.     

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.     

Immunochemiluminometric assay of creatine kinase MB with a monoclonal antibody to the MB isoenzyme

Previous two-site immunometric assays for creatine kinase (CK; EC 2.7.3.2) MB isoenzyme have been based on formation of a "sandwich" complex involving CK-MB and antibodies that recognize the CK-MM and the CK-BB isoenzymes. Single-incubation model assays of CK-MB with these antibodies were susceptible to interferences by CK-MM and CK-BB. We produced two anti-CK-MB monoclonal antibodies and studied their suitability for two-site assays. Both antibodies were compatible with anti-CK-MM and anti-CK-BB, but not with each other. Using anti-CK-MB as the tracer antibody eliminated the interference by both CK-MM and CK-BB. Labeling anti-CK-MB with acridinium ester and immobilizing anti-CK-BB on paramagnetic particles, we developed a rapid and highly sensitive chemiluminescent/magnetic separation CK-MB assay. As little as 1 microgram of CK-MB per liter was detectable after 10- or 30-min incubation at room temperature, and the standard curve was linear up to 400 micrograms/L. Results for serum samples by the new assay correlated well (r = 0.94) with those by Corning electrophoretic and the Hybritech Tandem-E immunoenzymometric CK-MB methods. Sera containing macro CK-1 or high concentrations of CK-MM and CK-BB did not interfere. The combined advantages of a more-specific antibody, paramagnetic solid phase, and chemiluminescent label endow this two-site CK-MB assay with performance characteristics and ease of use superior to those of previous assays.     

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.     

Highly sensitive enzyme immunoassay for human creatine kinase MM and MB isozymes

A sensitive enzyme immunoassay system for measurement of MM and MB forms of human creatine kinase (CK) was developed using purified monospecific antibodies to the M subunit and to the B subunit of CK. The CK-MM assay system consisted of polystyrene balls with immobilized F(ab')2 fragments of anti-M and the same antibody Fab' fragments labeled with beta-D-galactosidase from Escherichia coli. The CK-MB was assayed with the polystyrene balls with either antibody (anti-M or anti-B) F(ab')2 fragments and the other antibody (anti-B and anti-M, respectively) Fab' fragments labeled with galactosidase. The assays were highly sensitive and 3 pg of CK-MM and CK-MB were measurable. The CK-MM assay was specific to the M subunit of creatine kinase, and it cross-reacted about 15% with CK-MB, but not with CK-BB. The CK-MB assay did not cross-react with CK-MM nor CK-BB. Therefore, concentrations of CK-MM could be estimated by subtracting the cross-reacting values of CK-MB. Coefficients of variation in within-run and between-run precision studies for serum CK-MM and CK-MB were less than 9%. Serum levels in healthy adults of various ages (16-59 yr old) were ranged from 35.2-132 ng/ml for CK-MM and from 0.40-1.77 ng/ml for CK-MB. There was apparently no statistical significance among the sex- and age-related differences. Concentrations of CK-MM and CK-MB in various human tissues were also determined. The CK-MM was present abundantly in the heart and the tissues composed of striated muscles (skeletal muscle, diaphragm and proximal esophagus). The CK-MB was distributed not only in the heart but also in the striated muscle tissues at a relatively high level.     

Reassessment of creatine kinase BB as a marker for cancer of the prostate, breast, and lung

We used an enzyme-linked immunoabsorbent assay to measure creatine kinase (CK; EC 2.7.3.2) BB in the sera of 58 cancer patients. A pre-incubation step with an anti-CK-M antibody-coated bead removed M chain components, and CK-BB was quantified with use of an anti-CK-B antibody-coated tube. No cross reactivity was observed with mitochondrial CK or CK-MM; CK-MB cross reacted slightly (1.6%). Macro CK type 1 was measured as CK-BB. Average analytical recovery of purified CK-BB added to serum was 97.7%. Although the enzyme activity of CK-BB is labile, our studies show that this protein is antigenically stable for 12 months when stored frozen. The upper limit of normal for CK-BB concentration was 0.3 micrograms/L (95th percentile, n = 25). Of the 20 cases of breast cancer of various stages, none showed any increases of serum CK-BB. Only two of 18 patients with prostatic carcinoma (stage D), and two of 10 patients with oat-cell carcinoma of the lung had increased concentrations of CK-BB in the serum. Ten patients with squamous cell cancer of the lung had normal concentration of the enzyme. Thus the CK-BB isoenzyme is not frequently increased in cancers of the prostate, lung, and breast, and it has little apparent value as a tumor marker for these diseases.     

影响肌酸激酶同工酶活性检测结果的因素探讨

目的探讨应用酶免疫抑制法检测血清肌酸激酶（CK）同工酶——CK—MB酶活力单位时,引起临床假阳性的因素,以科学合理地解释每一检测结果及解决方法。方法采用回顾性研究,分析125例非心肌梗死患者,应用酶免疫抑制法检测血清标本中CK、CK—MB酶活力单位,分析可能引起检测值CK—MB酶活力单位假性升高的影响因素。结果86例成人非心肌梗死患者中,总CK活力相对较低,癌症患者、脑梗死患者、变态反应疾病患者CK—MB假阳性比例较大,其中CK—MB占CK总活力大于5％有59例,其中53例在6％～21％,6例大于38％;38例新生儿中CK活性范围为145～1974U／L,其中1例新生儿呼吸窘迫综合征患儿CKMB占CK总活力达90％;另1例溶血标本也引起假阳性。结论应用酶免疫抑制法检测非心肌梗死患者CK—MB酶活力单位假性升高的影响因素,可能是血清中存在巨CK、CK—BB、AK等,影响试剂单克隆抗体与肌酸激酶中的M亚基结合,存在未被抑制的CK—M、M亚基同时与B亚基参加酶促反应,而且因计算时结果乘以2,更加扩大误差,是该方法学缺点造成的错误结果,不能作为诊断依据。     

Appearance of a cathodic band in the electrophoretogram of blood creatine kinase isoenzyme-MM fraction during hypoxia in rats

In electrophoretograms of creatine kinase (CK; EC 2.7.3.2) in patients' blood, a band, presumably of mitochondrial origin, is occasionally observed on the cathodic side of the CK-MM fraction. We studied the implications of this phenomenon in rats exposed to hypoxic conditions. In the hypoxic cardiac muscle, the proportions of CK-MB and CK-MM were not significantly different from controls, but that of the mitochondrial CK was lower. In the corresponding blood, the cathodic mitochondrial CK band appeared, but disappeared as the animals recovered from hypoxia. The CK-MB isoenzyme was increased in the blood of the control rats, as obtained by heart puncture, but no mitochondrial fraction was detected. We believe that changes in myocardial mitochondria during hypoxia are related to the appearance of the cathodic band. Cytoplasmic CK-MB, unlike mitochondrial CK, markedly increased in the rats' blood during the recovery stage rather than during the hypoxia.     

Direct measurement of creatine kinase-MB activity in serum after extraction with a monoclonal antibody specific to the MB isoenzyme

Fusion of splenocytes from A/J mice immunized by creatine kinase (EC 2.7.3.2)-MB isoenzyme (CK-MB) with SP2/0-Ag14 myeloma cell line generated hybridomas producing monoclonal antibodies specific to CK-MB. One of these monoclonal antibodies ("Conan-MB") was used to develop a direct assay for CK-MB activity. In the assay, serum is incubated for 30 min at room temperature with "Conan-MB" immobilized on latex beads. The beads are then washed, and CK-MB activity bound to the antibody is measured after incubation with CK enzyme reagent for 30 min at 37 degrees C. Results with the assay correlated well (r = 0.997) with those for CK-MB concentration as measured by a two-site immunoassay. Neither CK-MM, CK-BB, mitochondrial CK, nor a hemolysate of erythrocytes interfered. Use of this unique monoclonal antibody allows rapid, precise, and direct determination of CK-MB activity.     

Stability and electrophoretic characteristics of creatine kinase BB extracted from human brain and intestine

Creatine kinase (CK; EC 2.7.3.2) isoenzyme BB extracted from brains of rats reportedly undergoes modification at 37 degrees C, leaving an electrophoretic variant that accounts for most of the residual CK activity. This variant, called CK-BB', migrates on electrophoresis similarly to creatine kinase isoenzyme MB. Using electrophoresis and immunoinhibition with antiserum to creatine kinase isoenzyme MM, we found CK-BB to be the only identifiable cytoplasmic isoenzyme in surgical samples from human brain and intestine. In contrast, we found that some samples of brain obtained at autopsy contain CK-BB'. We also found that CK-BB extracted from human brain was converted to CK-BB' upon incubation in serum or plasma at 37 degrees C. We found a similar development of CK-BB' in incubation mixtures of serum or plasma containing CK-BB obtained from surgical samples of human intestine. The development of CK-BB' during infarction of the gastrointestinal system may thus be a source of false-positive CK-MB in the laboratory verification of myocardial infarction when electrophoresis is used as the only method to identify CK isoenzymes.     

Influence of autoantibodies to creatine kinase-BB on assays for MB isoenzyme

We describe the influence of autoantibodies that bind creatine kinase BB (CK-BB) on the methods for MB isoenzyme. If these autoantibodies are present in patients' sera, they cause the formation of macro CK type 1 (immunoglobulin-linked CK-BB). In some of these cases they can bind not only endogenous CK-BB but also CK-MB without significantly affecting enzyme activity. Although these antibodies show distinctly less affinity for CK-MB than for CK-BB, they nevertheless bind CK-MB in these particular sera, because their concentration exceeds that of CK-BB isoenzyme. If a person with such autoantibodies has an acute myocardial infarction, the immunoinhibition method for CK-MB, which does not discriminate between CK-MB and CK-BB, will recognize the increase and peak of CK-MB with time, although persistent macro CK activity will be superimposed on the typical isoenzyme pattern. However, isoenzyme electrophoresis and recently introduced immunoenzymometric assays for CK-MB in these cases may be less sensitive for detecting myocardial infarctions, because the typical increase in CK-MB activity may be identified later in the progression of symptoms, or even be missed.     

Evaluation of hypoxic brain injury with spinal fluid enzymes, lactate, and pyruvate.

OBJECTIVE: To investigate the prognostic importance in neurologic recovery of the lumbar cerebrospinal fluid (CSF) variables creatine kinase (CK) and brain-type creatine kinase isoenzyme (CK-BB), lactate dehydrogenase (LDH) and its isoenzymes (LDH 1-5), CSF acid phosphatase, beta-D-N-acetylglucosaminidase activity, and CSF lactate, pyruvate, sodium, potassium, and calcium concentrations in patients who experienced cardiac arrest. DESIGN: Prospective clinical study with blood and CSF samples collected 4, 28, 76, and 172 hrs after resuscitation. SETTING: Medical ICU in a university hospital. PATIENTS: Twenty consecutive victims of out-of-hospital cardiac arrest. Eight patients recovered neurologically and 12 patients remained comatose or neurologically disabled until death. MEASUREMENTS AND MAIN RESULTS: CSF CK, CK-BB, LDH, and LDH isoenzyme 1-3 concentrations in all disabled patients were markedly increased at 76 hrs after the resuscitation. However, these variables were not changed in the recovered subjects. Patients (n = 7) with a mean CSF CK level of 25 +/- 33 (SD) U/L, CK-BB 23 +/- 33 U/L, and CSF lactate 3.8 +/- 0.9 mmol/L at 28 hrs after cardiac arrest remained unconscious and died. In the recovered patients, the mean CSF CK concentration was 2.0 +/- 1.5 U/L (p less than .001) and CSF lactate concentration 2.5 +/- 0.5 mmol/L (p less than .002). The lactate concentration was highest at 4 hrs after resuscitation, declining thereafter. Patients with a mean CSF total LDH level of 609 +/- 515 U/L and acid phosphatase 2.4 +/- 1.2 U/L 76 hrs after resuscitation died without regaining consciousness. In the recovered patients, the mean total CSF LDH activity was 82 +/- 58 U/L (p = .003) and CSF acid phosphatase was 0.8 +/- 0.5 U/L (p = .01) 76 hrs after resuscitation. CONCLUSIONS: CSF CK, CK-BB, and CSF lactate concentrations reflect a patient's outcome most reliably when measured within 28 to 76 hrs of the cardiac arrest. Similarly, CSF LDH, its isoenzymes 1-3, and CSF acid phosphatase concentrations, when measured at 76 hrs, can be used to monitor the patient's outcome after cardiac arrest. When correlated with Glasgow Coma Scale scores, the closest negative correlation was again seen in CSF CK and CK-BB at 28 and 76 hrs, as well as in LDH, LDH1-3, and acid phosphatase values at 76 hrs. The negative correlation between CSF lactate and Glasgow Coma Scale scores was most distinct at 28 hrs.     

Comparison of enzymatic characteristics of creatine kinase BB from human healthy and tumor stomach tissues

Creatine kinase (ATP: creatine N-phosphotransferase, EC 2.7.3.2, CK) BB isoenzyme from stomach tumor tissue was partially purified and its characteristics were compared with those from healthy tissue. Molecular mass of tumor CK-BB was estimated to be 82 000 by polyacrylamide gel electrophoresis. Tumor CK-BB was separated into 2 main subbands around pH 4.5 and 11, minor subbands around pH 5-7.5 by agarose isoelectric focusing. The isoenzyme reacted with anti-human brain CK-BB antibodies and formed a hybrid, CK-MB, with CK-MM prepared from healthy human skeletal muscle. The above physicochemical and immunological characteristics of tumor CK-BB were the same as those of normal CK-BB from normal stomach tissue. Optimum pH of tumor CK-BB was more acidic than that of normal CK-BB. Affinity for creatine phosphate and heat sensitivity of tumor CK-BB were slightly lower than those of normal CK-BB. Tumor CK-BB was more stable after iodoacetamide and urea treatments.     

Clinical role of recurrently elevated macro creatine kinase type 1

The typical creatine kinase (CK) isoenzymes include CK-BB, CK-MB, and CK-MM. Macro CK type 1, one of the atypical CK enzymes, has been identified in human serum, but the clinical significance still remains uncertain. In our laboratory, 105 patients who expressed serum macro CK isoenzyme type 1 were identified from March 2004 to March 2007. We found that macro CK type 1 recurred after at least one month in 16 patients. Clinical diagnoses were myopathy in 14 patients, sepsis in one, and acute coronary syndrome in one. The averages of serum total CK and macro CK type 1 were 9,132 and 1,925 (U/L), respectively. The linear regression analysis between recurrent macro CK type 1 and total CK revealed a good correlation (y=3.5054x+2381.3, R(2)=0.7822, P<0.001). Three patients had critical illness, including one respiratory failure and two mortalities. Good linear correlation is documented between total CK and recurrent macro CK type 1. In conclusion, the macro CK type I isoenzyme recurred primarily in patients with myopathy.     

Monoclonal antibody inhibiting creatine kinase MM3 but not isoform MM1

Monoclonal antibody CKM-G01 inhibited greater than 99% of the activity of porcine and human creatine kinase(CK)-MM isoenzyme purified from muscle. However, it inhibited only 54% of CK-MM in human serum. Chromatofocusing of serum CK-MM showed that CKM-G01 inhibited 100% of MM3 but not isoform MM1. CKM-G01 inhibited CK-MM2 by 57%. CKM-G01 specifically inhibited only the original CK-M subunit and not the subunit modified by removal of C-terminal lysine by carboxypeptidase N. CKM-G01 can be used for assay of CK isoforms. We devised a new diagnostic reagent involving it, which requires no analytical separation of isoforms, based on the immunoinhibition method, and applied it to early diagnosis of acute myocardial infarction. The "inhibition index," (inhibited CK activity/total CK activity) x 100, increased more rapidly than did total CK and CK-MB. Evidently this diagnostic reagent can be used for easy, early diagnosis of acute myocardial infarction.     

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.     

Transient increase in serum creatine kinase isoenzyme BB activity after prostatectomy in a patient with massive benign prostatic hyperplasia

The activity of creatine kinase isoenzyme BB (CK-BB) in serum is rarely abnormally high (i.e., detectable). An increase in immunoreactive CK-BB or CK-BB activity in patients with prostatic disease has been proposed as an indication of prostatic adenocarcinoma. Here we report the case of an elderly man with massive benign prostatic hyperplasia but no clinical or pathological evidence of prostatic adenocarcinoma, whose serum CK-BB activity was found by agarose gel electrophoresis to be 1 U/L (normal: 0%), 10% of his total CK activity. Serum CK-BB activity was further increased to 16 U/L (20% of total CK activity) 1 h after prostatectomy, but became undetectable by the second day after the operation. The findings suggest that: (a) the source of the serum CK-BB activity was the enlarged prostate gland; (b) abnormally high CK-BB activity in serum of men with prostatic disease does not necessarily indicate the presence of prostatic adenocarcinoma; and (c) myocardial injury could be erroneously diagnosed postoperatively in prostatectomy patients if CK isoenzyme methods are used that do not consistently separate "heart-specific" CK-MB from CK-BB.     

Determination of creatine kinase isozymes in sera and tissues of patients with various lung carcinomas

Three creatine kinase isozymes (CK-BB, CK-MB and CK-MM) were estimated by immunoassay in tumor tissues and in sera of patients with various lung carcinomas. CK-BB was increased in small cell carcinoma, but not in other lung carcinomas. CK-MM and CK-MB were not increased in any types of carcinoma. Serum CK-BB was increased in all types of lung carcinoma examined, while serum CK-MM and CK-MB were within normal limits in all patients. Serum CK-BB of healthy adults was estimated as 0.32 +/- 0.14 (mean +/- SD) ng/ml, ranging from 0.11-0.68 ng/ml. If CK-BB values above 1.0 ng/ml were considered abnormal, elevation occurred in 28/40 (70%) of patients with small cell carcinoma, 25/67 (37%) with adenocarcinoma, 21/51 (41%) with squamous cell carcinoma, 4/11 (36%) with other carcinoma of the lung and 10/42 (24%) with lung tuberculosis. Since serum CK-BB with lung cancer changed in parallel with the clinical course, this isozyme may be a marker for monitoring the clinical course, especially in small cell carcinoma of the lung.     

Simultaneous automated measurement of serum total CK and CK-MM lsoform ratio in serum

We automated a two-step kinetic procedure for determining serum CK-MM isoform ratio using an immunoinhibition method. By measuring the total CK activity and the residual CK activity (serum CK-MM isoform) remaining after the inhibition by tissue CK-MM isoform specific monoclonal antibody reagent (CK-M01) the CKMM isoform ratio is calculated using the difference between total CK and residual CK activities divided by the residual CK activity. Linearities of total CK and residual CK assays were?7750 U/L and 2,500 U/L, respectively; within-run CVs of isoform ratio (N = 10) were 2.8 and 7.0% (mean 0.14 and 0.60), respectively. The MM³/MM¹ isoform ratio obtained with the proposed method (X) correlated well with the results of electrophoretic method (Y) according to the equation: Y = 0.98X ?0.3, r = 0.988. The normal reference range of isoform ratios obtained by assaying 1,222 serum samples from healthy subjects was 0.09–0.75. The isoform ratio increased after onset of chest pain, peaking at 2–6 hr thereafter. A mean isoform ratio of 1.86 was obtained with serum sample from 86 patients diagnosed as having an acute myocardial infarction (AMI). This method is accurate and highly sensitive, as the detection and early diagnosis of AMI can be completed in 10 min. © 1994 Wiley-Liss, Inc.