Nonspecific binding is binding of the assay antibodies which is not correlated with the specificity of the antibodies. Also analytes can bind non-specifically.
There are two kinds of nonspecific binding which normally occurs in the lab and which can not be distinguished from each other easily.
On the one hand there is nonspecific binding to surfaces like ELISA wells or Western blotting membranes. The results are e.g. high background or false positive results in ELISA. The second reason for nonspecific binding also can lead to high background in ELISA. Reason is binding to substances in solution which are present in high concentration e.g. albumin or immunoglobulin. This effect can be prevented by using modern buffer like LowCross-Buffer®. Even nonspecific binding of analytes can also cause wrong low results instead of false positive results. This happens if the analyte is partially and nonspecifically bound to albumin or other constituents of the sample. The so masked analyte can not be detected by the assay antibodies. In this case LowCross-Buffer® can help as well.