Expression of dose-response curves in standard units

This method (De Savigny and Voller, 1980) has the advantages that the absorbance values are transformed into quantitative units on a continuous scale, that the sera are tested at a single dilution and that the results are proportional to the titres. However, as with all absorbance-based methods, it is not valid at high absorbance values. Furthermore, a rigorous quality control is required and the dose-response curves are assumed to be parallel. 

A variant of this method was described by Malvano et al. (1982) standard unit response curves are constructed with aliquots of a highly positive serum diluted with a negative sample. This approach is based on the assumption that dose-response curve parallellism eliminates the necessity to employ many different sera for the calibration curve. This positive serum is then calibrated against a WHO standard serum and the antibody content of the positive serum is expressed in international units (lU). Calibration samples of the positive serum diluted with a negative serum are included as internal markers for between-run, between-laboratory and between-method normalizations to provide analytical consistency to the measurements. 

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