Supporting information and resources
Total protein is a non-specific measure of the total amount of all proteins present in a solution. It is used to examine changes in overall protein secretion in blood or saliva that are associated with disease states, or to look for differences in the ratio of specific proteins (or other analytes) to total protein that exist in different oral fluids or that occur in response to physiological changes or disease states. (1,2,3,4,5,6) Total protein is also sometimes used to normalize concentrations of various salivary proteins such as SIgA in different samples, since concentrations can vary significantly in response to stimulation or alterations of saliva flow. (5) It has been suggested, however, that this practice may be misleading because of differences that exist in the control of secretion of individual salivary proteins among the different salivary glands. (7,8,9) Changes in total protein in saliva and gingival crevicular fluid have been examined in relation to the presence of periodontal disease, and it may have some use as a marker of certain disease conditions. (10,11) Our laboratory uses a Pierce bicinchoninic acid assay (BCA assay), which is compatible with various chemicals in buffers that can cause interference in other protein determination methods, such as the older Lowry method.