Acute-phase protein detection and quantification in gingival crevicular fluid by direct and indirect immunodot

The development of an assay for markers of active periodontitis, obtained directly from gingival crevicular fluid (GCF) and simply quantified, would be of great importance to the dental practitioner. The purpose of this study was to evaluate direct and indirect immunodot techniques as to their potential in easily quantifying acute-phase proteins within periodontally diseased and healthy site GCF. Indirect immunodots (GCF eluates dotted onto nitrocellulose membrane) using monoclonal antibodies and a radioactive isotope label were used to identify and establish relative amounts of C-reactive protein (CRP) and alpha-2-macroglobulin (A2M) in 2 diseased and 2 healthy sites in 24 periodontitis patients. Periodontally diseased sites were found to contain significantly lower concentrations of A2M than healthy sites (p less than 0.001), but CRP levels did not vary significantly between healthy and diseased locations. Using a direct immunodot assay (GCF absorbed directly into nitrocellulose membrane strips), A2M levels quantified with radioactive isotopes at healthy and diseased sites could be correlated with A2M levels determined by enzyme-linked antibody-colormetric probes at those same sites. Such a direct sampling and quantification system shows promise for future "in-office" diagnostic methodology.