Validation of Salivary Antimicrobial Peptides as Diagnostic Periodontal Biomarkers

We have previously shown that salivary concentrations of the Antimicrobial Peptides (AMPs) HNP1-3 and S100A8 may be useful biomarkers of periodontal disease, and may discriminate between gingivitis and periodontitis.   The aim of this study is to test the validity of these putative biomarkers by testing their ability to identify patients with periodontitis in an independent cohort of subjects.

Methods:

70 unstimulated saliva samples (47 with Chronic Periodontitis, 23 with Gingivitis) were tested by ELISA for HNP1-3 & S100A8.  ROC curves were constructed to determine cut off points for optimum utility to discriminate between periodontitis and gingivitis.  In addition both markers were combined to give a single combined cut off point by normalising each biomarker to percentage of cut off point value, (such that x + y = combined cut off point). 

Results:

Within the independent cohort application of predetermined cut off points for HNP1-3 detected severe periodontitis with 83.45% specificity and 44% sensitivity and for S100A8 79% specificity, 32 % sensitivity against controls.  A combined test for HNP1-3 + S100A8 increased specificity to 92%, with 32% sensitivity.   Results were independent of diabetic status of subjects.

Conclusions:

Application of predetermined cut off points of HNP 1- 3 and S100a8 detected periodontitis cases with moderate specificity and low sensitivity.  A composite biomarker of HNP 1- 3 + S100a8 gave markedly superior specificity than either biomarker individually, but the sensitivity of the test remained low.