[Variant creatine kinase isoenzymes: frequency and clinical significance (author's transl)]. / Atypische Kreatinkinase Isoenzyme. Inzidenz und klinische Bedeutung.

To estimate the incidence of variant creatine kinase (CK)isoenzymes, 1,191 unselected patients were screened by means of CK:CK - MB ratio. When CK - MB was higher than 20% of the total CK in the immunoinhibition test, and a myocardial infarction could be excluded, a CK-isoenzyme electrophoresis was performed. We found macro-CK-BB-emia in 13 patients, but only three of them had elevated total CK activity. All patients but two were at the typical age of over 60 years; two males were 2 and 9 years old. The clinical diagnosis in macro-CK-BB-emia was predominantly cardiocerebrovascular insufficiency due to arteriosclerosis. In 16 other patients, the presence of an isoenzyme migrating cathodically to CK-MM was found. In this group, a malignant metastatic tumor was found in eight cases, the rest predominantly suffered from severe liver disease. Presence of both variant CK isoenzymes may lead to diagnostic or therapeutic errors due to the altered CK:CK-MB ratio. According to our studies, a variant CK isoenzyme occurs in 2.6% of hospitalized patients, but this will lead to problems diagnosing acute myocardial infarction only in the group with elevated total CK (0.42% of our patients).

Evaluation of a monitor guided nephelometric system.

The most common parameters in the specific protein field, namely the immunoglobulins G, A and M were investigated on the recently developed Immuno Video Nephelometer System (IVNS). This system consists of the nephelometer, a microprocessor controlled program and a monitor screen, where instructions, standard curve and results are displayed. Scattered light of immuno-complexes is measured at equilibrium after incubation of prediluted antigen-antibody mixtures. Data were compared with those obtained by radial immunodiffusion (RID), rate nephelometry (Beckman Immunochemistry System-ICS) and immunoturbidimetry (ENI-Gemsaec). Intrabatch variation on the Immuno Video Nephelometer System was found to be good (CV-2.6-3.7%) and day to day variation was satisfactory (CV-3.3-8.6%). There was also good correlation between the values found on the Immuno Video Nephelometer System and those of the other methods (correlation coefficient of 0.94-0.98). Instrumentation advantages, operation procedure and necessity of antigen excess check are discussed in detail.

Immunoinhibition and automated column chromatography compared for assay of creatine kinase isoenzyme MB in serum.

We examined sera from six different groups of patients for CK-MB activity by means of two commercially available tests, an immunoinhibition method (E. Merck) and the CK-MB test as used with the aca (Du Pont). In the first group of patients (suspicion of myocardial infarction) the correlation between the two methods was good: r = 0.9191, y = 1.068x -- 0.888, x = 18.7 U/L, y = 19.0 U/L. In the second group, patients with high adenylate kinase activity, no interference was detectable on the aca, whereas the immunoinhibition method yielded falsely high CK-MB values. The third group consisted of persons with macro-CK-BB in their serum. In the immunoinhibition test these patients usually showed a high CK-MB:total CK ratio, whereas such results were rarely found for the aca. The fourth group, patients with a different electrophoretic mobility of their CK-isoenzymes (migration of an active band towards the cathode), were detected by the immunoinhibition method (high ratio of CK-MB to total CK), but not with the aca. In the presence of free CK-BB (group five) the immunoinhibition test resulted in "falsely" high CK-MB values, whereas CK-BB was retained on the column of the aca. In skeletal muscle diseases (group six) results by the two methods differed, values for CK-MB on the aca being much higher. It was demonstrated experimentally that this was due to CK-MM with altered surface charge.

Intestinal alkaline phosphatase and the ABO blood group system--a new aspect.

The influence of erythrocytes of different blood groups on the intestinal isoenzyme of alkaline phosphatase (EC 3.1.31.1) was investigated. Binding of the enzyme to erythrocyte membranes was demonstrated by sedimentation experiments, by enzyme electrophoresis, by gel chromatography and immunologically using a modified Coombs technique. We found that red cells of blood group A bind almost all intestinal alkaline phosphatase; erythrocytes of blood group B or O to a much lesser degree. This is in accordance with the fact that intestinal alkaline phosphatase is found more frequently in the serum of individuals of blood group O or B than in serum of persons of blood group A. We conclude that underlying the described blood group dependent differences in synthesis of intestinal alkaline phosphatase lies a mechanism involved in the regulation of the activity of intestinal alkaline phosphatase in human serum.