Common salivary protein 1 in saliva of diabetes patients (II)

Background: Human common salivary protein 1 (CSP1) is one of a variety of molecules in saliva but its function remains to be determined. The gold standard method for diagnosis of diabetes mellitus (DM) is to check levels of glucose or HbA1C in plasma or serum. The purpose of this study was to examine whether Salivary CSP1 concentration would be useful alternative for DM diagnosis. Methods: The qualities of monoclonal antibodies (mAbs) to recombinant human CSP1 (rhCSP1) were tested by western blotting (WB) and immunohistochemistry. A sandwich ELISA was fabricated with the qualified capture and detector mAbs for measurement of CSP1 level in saliva. CSP1 levels of healthy adults and DM patients were measured by the sandwich ELISA and their results were statistically analyzed by Student's t-test. The receiver operating characteristic (ROC) curve was constructed and the area under the curve (AUC) was calculated. Results: The tested mAbs recognized a 27-kDa CSP1 of saliva in WB and stained only a salivary gland in immunohistochemistry. Pearson's correlation coefficient with standard curve between OD450nm value vs. CSP level showed good linearity (r2 = 0.995). The median values (25th to 75th percentiles) of saliva CSP1 in 10 healthy adults and 18 DM patients using the sandwich ELISA were 3.92 μg/mL (3.15 - 4.02) and 4.35 μg/mL (3.94 - 5.11), respectively. Statistically, there was a significant difference of CSP1 level in two groups (p = 0.026). The sensitivity value of CSP1 was 64.71 while the specificity value was 88.89 with 0.784 of AUC (p = 0.003). These results suggested that the fabricated sandwich ELISA was a good diagnostic test tool for discriminating DM patients from healthy individuals. Conclusions: The present data showed a significant increase of CSP1 levels for DM patients compared with control group, indicating that CSP1 level in saliva could be used as a potential biomarker of detection or screening of DM patients. However, further studies are necessary to provide scientific and clinical validation.