A web-based method for computing endpoint titer and concentration of antibody/antigen

Abstract

In this report, we describe a web server for calculating the endpoint titers and concentrations of antibody/antigen (Ab/Ag) from the optical density (OD) taken from ELISA data. The server utilizes a graphical method (Raghava et al 1992) for determining the concentration of either the antibody or the antigen. In order to calculate the endpoint titer, we first fit the OD versus concentration of control data using a least-squares curve-fitting method. Then we fit the OD versus concentration of the standard sample using a graphical method. Finally, we determine the intersection or nearest point of the two curves, which we have called the endpoint titer. In order to calculate concentrations of the antibody/antigen of unknown samples, we have to first fit OD versus the concentration of the known samples using a graphical method and to determine the linear interpolation and hyperbolic formulas. Then we calculate the concentration of the unknown samples from their OD using these formulas. This web server utilizes a CGI program written in Perl and Javascript, which makes the server live and interactive (imtech.res.in/raghava/abag/).