Imprecision of quantification of serum protein fractions by electrophoresis on cellulose acetate

We studied the precision of densitometric quantification of the protein zones resolved by cellulose acetate electrophoresis. Replicate analyses of patients' samples by a single technologist showed mean CVs ranging from 2.9% for serum albumin to 9.5% for alpha 1-globulin. There were marked differences in measurements obtained by replicate analysis of the same samples by two experienced technologists. We calculated what changes in fractional concentrations would be analytically significant and concluded that densitometry of cellulose acetate electrophoretograms can only be semi-quantitative. We suggest that visual interpretation of high-resolution electrophoretic patterns by a trained observer can replace densitometry in most cases.