Prognosis versus actual outcome. IV. The effectiveness of clinical parameters and IL-1 genotype in accurately predicting prognoses and tooth survival

Background: Recently, a genetic marker (IL-1 genotype) that identifies indi viduals at higher risk for developing severe periodontal disease was discov ered. A subgroup of the population reported on earlier was evaluated to det ermine if knowledge of the patient's IL-1 genotype would improve accuracy i n assignment of prognoses and prediction of tooth loss. Methods: This subgroup consisted of 42 patients (1,044 teeth) in maintenanc e care for 14 years; 16 tested IL-1 genotype-positive (IL-1GP). Nine were s mokers, and 30 had a history of smoking, with an average of 29.44 pack year s. A multiple Cox regression model and Kaplan-Meier survival plots were fit to the subset of patients to evaluate tooth loss. Results: Both IL-1GP and heavy smoking were significantly related to tooth loss. A positive IL-1 genotype increased the risk of tooth loss by 2.7 time s, and heavy smoking by 2.9 times. The combined effect of IL-1GP and heavy smoking increased the risk of tooth loss by 7.7 times. The value of clinica l parameters traditionally used to assign prognosis was found to be depende nt on IL-1 genotype and smoking status. In the model that included IL-1 gen otype and heavy smoking, none of the clinical parameters added significantl y to the model for tooth loss while mobility, probing depth, crown-to-root ratio, and percent bone loss added significantly to the model, which includ ed IL-1 genotype in non-smokers. IL-1GP patients and patients who smoked he avily demonstrated a much worse tooth survival rate when compared to IL-1 g enotype-negative patients and non-smokers, respectively, Conclusions: Knowledge of the patient's IL-1 genotype and smoking status wi ll improve the clinician's ability to accurately assign prognosis and predi ct tooth survival. Clinical implications are as follows. Investigators were unable to judge which patients would be IL-GP or negative based on their c linical presentation or family history of tooth loss due to periodontal dis ease. Since periodontal diseases are multifactorial, knowledge of the patie nt's genotype is more important in predicting future risk than explaining p ast disease. Knowledge of IL-1 genotype status would be important in develo ping a treatment plan and predicting tooth survival for a new patient who s mokes and presents with periodontal disease, especially if restorative care is needed. Knowledge of a maintenance patient's IL-1 status would help tar get therapy for non-responding areas; one would be less likely to take a "w ait and see approach" with IL-1GP patients. IL-1 positive non-smokers can b e successfully treated and maintained over long periods of time.