The analysis of data from breast cancer estrogen and progesterone receptor assays: Scatchard plots are inferior to direct fitting by computer.

The advantages are illustrated of analyzing breast cancer estrogen and progesterone receptor assays by fitting a receptor-ligand binding model directly to experimental data, rather than using the common graphical transformation known as the 'Scatchard plot'. Analysis of laboratory experiments and the use of simulation show that while both methods give equivalent results, the direct approach has definite advantages. In particular, results are more reliable in the face of increasing experimental error, it is possible to quantify non-specific binding from the primary data rather than having to measure it separately, and the methodology readily lends itself to optimizing the design of experiments.