Quantitative analysis of samples using a a Point-to-Point linear regression suitable for Concentrations are determined for samples outside the range of the standards by extrapolating the first and last point pairs. sigmoidal data. All samples are first corrected by the mean of the blank group measurements. The standard data points are plotted (concentration vs. corrected measurement) and a a Point-to-Point linear regression is made through these points. The concentrations of the unknown samples are determined from the fit. It is important to note that concentrations can only be determined for samples which fall within the range of the determined upper and lower asymptotes of the fit (the a and d parameters).

Quantitative in vitro assay for human IgM rheumatoid factors (autoantibodies of the IgM class against human IgG) in serum or plasma. This method calculates concentration of antibodies in the serum samples using point-to-point plotting of the extinction values measured for the 3 calibrators (standards) against the corresponding units (linear/linear). Samples greater than the first calibrator are marked as “> Standard1”.