FIG 2.

Detection range. WHO international standard plasma 20/136 (1,000 BAU/mL) was serially diluted with serum dilution buffer (SDB) (1× PBS [pH 7.4], 0.05% ProClin 300, 0.01% phenol red) to simulate samples with antibody concentrations ranging between 0.1 BAU/mL and 1,000 BAU/mL. Simulated samples were tested with ELISA 1 (open circles) (final in-well dilutions of 1:100 for samples and 1:20,000 for the conjugate) and ELISA 2 (filled circles) (final in-well dilutions of 1:2 for samples and 1:50,000 for the conjugate). Dotted lines indicate A₄₅₀-A₆₂₀ values of 0.2 and 0.4, respectively. Solid lines indicate the linear regression fit.