Interlaboratory survey of Enzyme Analyses iii. Does College of American Pathologists' survey serum mimic clinical specimens?

Participants in the last College of American Pathologists Enzyme Surveys in 1978 were asked that they provide results for lactate dehydrogenase (LD), alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine kinase (CK), for the six interrelated Enzyme Survey serum specimens, and were also asked to provide results for the same enzymes from six healthy persons and from 50 patients. Extensive data analysis revealed that porcine LD and CK in the Survey serum had kinetic properties similar to the native enzymes in fresh human serum. On this basis, we were able to merge the normal data from laboratories using diverse methods and to establish a "universal" reference range for these two enzymes. Survey serum may serve as a bridge for the clinical comparison of very diverse methods for determining LD and CK, possibly for AST and ALT, but not for ALP.

Intralaboratory survey of alkaline phosphatase methods.

Three sets of interrelated specimens containing alkaline phosphatase (ALP) were analyzed: CAP 1977 Enzyme Survey serum, human serum supplemental with calf intestinal ALP, and human serum with increased human liver ALP. Five quite distinct ALP methods were used. In addition, fresh serum from volunteer blood donors and serum from patients with increased serum ALP activities were examined by each of these five methods. Conversion factors for the five different methods based on results from calf-intestine-supplemented interrelated specimens could not be used to interconvert results for fresh human serum. However, the interrelated specimens with increased human liver ALP made interconversion of results for fresh human serum possible.

Apparent mitochondrial creatine kinase in the serum of a patient with metastatic cancer to the liver.

Creatine kinase (CK, EC 2.7.3.2) activity in the serum of a patient with metastatic carcinoma migrated as two distinct bands cathodal to the origin and to CK-3 on agarose gel electrophoresis. The more cathodal isoenzyme (CKm-2) is of high molecular mass, is precipitated by ammonium sulfate at 30% of saturation, and is not retarded by Sephadex G-100. Treatment with urea at a concentration of 6 mol/L caused CKm-2 to elute with proteins of lower molecular mass on a G-100 column and shifted the electrophoretic migration to a position just cathodal to the origin (CKm-1). Antibody to CK-1 and CK-2 did not affect the activity of either CKm-1 or CKm-2. Similarities between these cathodal bands of CK activity and mitochondrial CK suggest the mitochondrial origin of these isoenzymes. These cathodal CK isoenzymes reacted unpredictably with different commercial reagent systems for determination of CK activity in serum or in agarose gel.