The relationship of gingival fluid leukocyte elastase activity to gingival fluid flow rate

Recent studies have suggested that leukocyte elastase activity (EA) in tissue exudates is an indicator of inflammatory disease. We assayed gingival fluid (GF) EA with a selective peptide substrate and compared it to GF flow rate with regard to its ability to detect differences in the clinical status of existing inflammatory periodontal disease in 56 human subjects. Compared to healthy sites (Gingival Index = 0, 1 to 3 mm) and mild gingivitis sites (GI = 1, 2 to 5 mm), mean GF EA was significantly (P < 0.05) higher at periodontitis sites with deep probing depths (GI = 2, 6 to 9 mm depth), but not at periodontitis sites with intermediate probing depths (GI = 2, 4 to 5 mm). When expressed as specific EA (i.e., normalized to GF protein content), mean EA was also significantly higher at deep periodontitis sites compared to healthy sites and mild gingivitis sites. In addition, specific EA was significantly higher at periodontitis sites with intermediate probing depths than at healthy sites. As predicted by previous studies, these significant increases in specific EA were associated with significant increases in mean GF flow rate. In contrast to specific EA, however, mean GF flow rate was significantly higher at gingivitis sites than at healthy sites. A strong correlation was observed between GF flow rate and specific EA (rs = 0.737, P = 0.0006). Thus, GF flow rate and GF EA appear to be related indicators of inflammation, but GF flow rate may be more sensitive to early inflammatory changes leading to mild gingivitis.