Title: Periodontal Inflamed Surface Area (PISA)— Psychometric Evaluation and Biological Correlates of a Promising Index for Measuring Periodontal Inflammation
Description: Periodontal inflammation is a hallmark of periodontitis and a primary driver of progressive periodontal tissue destruction. In addition, inflammation is hypothesized as a critical mechanistic intermediate linking periodontal disease to systemic inflammation and extra-oral disease outcomes. However, most of the commonly used measures of periodontitis, for research and/or surveillance purposes, focus on quantifying the periodontal tissue loss (i.e., gingival recession (GR) and clinical attachment loss (CAL)). There are few indices that focus on quantifying periodontal inflammation in the periodontal literature, and there are inherent limitations in the way they are calculated. The Periodontal Inflamed Surface Area (PISA) is a composite measure that incorporates bleeding on probing (BOP) and other measures of periodontal disease to quantify the amount of periodontal inflamed surfaces. This dissertation examined PISA as a useful measure that attempted to quantify periodontal inflammation, and it is divided into three parts.

The first paper is a scoping review focused on reviewing the relevant literature around PISA since its introduction to the literature in 2008. The second paper is an empirical paper that examined the psychometric properties of PISA compared to other measures of periodontitis. The third paper is another empirical study that explored how PISA correlated with some biological features of periodontitis, including the subgingival microbial profile, systemic immune response, and selected dysbiosis indices. The empirical papers utilized data from two population-based cohorts: the Oral Infections, Glucose Intolerance, and Insulin Resistance Study (ORIGINS) and the Washington Heights Inwood Community Aging Project's Ancillary Study of Oral Health (WHICAP-OH). The review found that PISA was primarily utilized in studies that looked at oral-systemic health connections, with results that mostly confirmed the associations between periodontal disease and systemic health. However, most evidence suffered from methodological concerns that could limit the validity and generalizability of results.

The psychometrics analyses showed that PISA had good sensitivity, specificity, and accuracy in identifying patients with periodontitis. The latent factor analyses suggested a multi-level three-factor model showing PISA to cluster with bleeding on probing in the same factor that indicates an inflammation component of the unobserved periodontal disease status. The third paper showed that PISA was significantly associated with alpha diversity indices (Shannon's, Simpson's, and Faith's phylogenetic diversity) and two of the dysbiosis indices in both cohorts. The strength of associations and amount of variance explained in some of the biological features were higher for PISA than other measures of periodontitis. The evidence from this dissertation suggests that PISA is a valuable index that describes periodontal inflammation and has good psychometric properties. Future research can explore the replication of our methods in other cohorts to expand the validity and utility of PISA in periodontal literature.