Prediction of Periodontal Disease Progression During Supportive Periodontal Therapy Using an Oral Fluid Lactate Dehydrogenase Activity-Based Test Strip

<b>Background/Objectives</b>: Periodontal disease may progress despite supportive periodontal therapy (SPT), and conventional clinical parameters exhibit limited predictive value. This study evaluated the prognostic utility of measuring the oral fluid lactate dehydrogenase (LD) activity using a chairside test strip to predict disease progression during SPT. <b>Methods</b>: A cohort of 92 patients (33 males and 59 females; median age, 68 years) undergoing SPT at a university clinic in 2023 were followed up for approximately one year. Oral fluid LD activity was measured using a test strip, and clinical periodontal parameters were assessed at baseline and follow-up. Periodontitis progression was defined as ≥4 sites showing a 2 mm increase in the probing pocket depth, which reached ≥4 mm. Receiver operating characteristic analyses and stepwise logistic regression were used to evaluate the predictive performance of oral fluid LD activity and develop a multivariate model. <b>Results</b>: Seventeen patients (18.5%) developed progressive periodontitis. Progressive cases demonstrated significantly higher baseline LD activity and periodontal parameters. The optimal cutoff value for LD activity was 3.5, yielding a sensitivity, specificity, and negative predictive value of 1.00, 0.53, and 1.00, respectively. Logistic regression identified oral fluid LD and medications as independent predictors, with the multivariate model achieving an area under the curve of 0.785. <b>Conclusions</b>: Oral fluid LD activity measured using the test strip provided prognostic information for periodontitis progression during SPT. Incorporating LD with information obtained from medical interviews did not markedly enhance the predictive accuracy. This rapid and noninvasive method may facilitate risk-based patient management and personalized supportive care.