BIOLOGICAL VARIATION OF CARDIAC MARKERS - ANALYTICAL AND CLINICAL CONSIDERATIONS

The analytical, within-subject and between-subject components of varia tion were estimated for serum total creatine kinase (TCK) activity, CK -MB (creatine kinase-MB) activity, CK-MB mass, ratios of CK-MB activit y and CK-MB mass to TCK activity and myoglobin concentration in a coho rt of 16 apparently healthy subjects over 5 days. Analytical goals bas ed on biological variation showed that, for all quantities except CK-M B mass, methodological improvement is warranted. All cardiac markers s howed marked individuality which casts doubt on the utility of convent ional population-based reference values as interpretative criteria. Th e critical differences required for significance of changes in serial results differ markedly from marker to marker and the data allow gener ation of objective criteria for monitoring individuals.