Discrimination of refractory periodontitis subjects using clinical and laboratory parameters alone and in combination

The purpose of the present investigation was to use baseline clinical and l aboratory parameters to distinguish subjects refractory to conventional per iodontal therapy. Baseline clinical, microbial and host parameters were com pared in 61 successfully-treated and 27 refractory subjects. Refractory sub jects showed mean full-mouth attachment level (AL) loss and/or >3 sites wit h new AL loss >2.5 mm within 1 year after both scaling and root planing and surgery with systemic tetracycline. Successfully-treated subjects showed m ean AL gain and no sites with new AL loss >2.5 mm after either regimen. Gin gival redness, bleeding on probing, suppuration, supragingival plaque accum ulation, pocket depth and AL were measured at 6 sites per tooth in each sub ject. The levels of 40 subgingival taxa were determined in subgingival plaq ue samples from up to 28 sites in each subject using checkerboard DNA-DNA h ybridization. Serum antibody (Ab) to 85 subgingival species was determined using checkerboard immunoblotting. Levels of serum IgG2 and Gm23 allotype w ere measured using radial immunodiffusion; Fc gamma RIIa and Fc gamma RIIIb receptor haplotypes were determined using PCR and allele specific oligonuc leotide probes. Odds ratios of a subject being refractory were determined b y comparing measured parameters in the 2 subject groups using univariate an d multivariate techniques. 17 of 151 clinical, microbial and immunological variables were significant using chi(2) analysis after adjusting for multip le comparisons. For example, the odds ratios of a subject being refractory were 12.2, 5.4 and 6.9 if the subject had Ab >50 mu g/ml to >9 species; S, constellatus counts >2.4% of the total DNA probe count or >2.1% of sites wi th AL >6 mm. The 17 significant predictor variables were used in logistic r egression and discriminant analyses. Similar variables were selected using both analyses including the number of serum Ab to subgingival species >50 m u g/ml, % S. constellatus in plaque samples and % sites with attachment los s >6 mm. In the logistic regression analysis model, the odds ratios associa ted with >9 species exhibiting >Ab 50 mu g/ml, >2.1% of sites with AL >6 mm and >2.4% S. constellatus in plaque were 8.7, 6.8 and 2.4, respectively, a fter adjusting for other variables in the model. Discriminant analysis usin g these variables provided sensitivity, specificity, positive and negative predictive values of 0.66, 0.92, 0.80 and 0.85 respectively. Refractory per iodontitis subjects could be distinguished using a subset of clinical, micr obiological and immunological parameters.