A critical assessment of interleukin-1 (IL-1) genotyping when used in a genetic susceptibility test for severe chronic periodontitis

Background: This review addresses the ability of a commercially available genetic susceptibility test to determine the risk of developing severe chronic periodontitis. The test is used to detect the simultaneous occurrence of allele 2 at the IL-1A+4845 and IL-1B+3954 loci. If both of these polymorphisms are present, patients are referred to as being genotype-positive and considered predisposed to becoming afflicted with severe chronic periodontitis. A basic premise of this test is the assumption that individuals who are genotype-positive produce increased amounts of IL-beta in response to microbial lipopolysaccharides, which allegedly predisposes them to an exaggerated inflammatory response and an increased incidence of chronic periodontitis. Methods: Controlled clinical trials were selected that evaluated the ability of the genetic test to predict which patients were susceptible to bleeding upon probing, periodontitis, peri-implantitis, and tooth loss. Results: Comparison of results from test (genotype-positive) and control groups (genotype-negative) revealed that there is ambiguity with regard to predicting which patients will manifest elevated subgingival levels of IL-beta. Similarly, it is questionable if the test is able to forecast which individuals will demonstrate an increased occurrence of bleeding upon probing, diminished clinical attachment, decreased osseous support, or loss of teeth. Conclusions: There are many unanswered questions concerning the utility of detecting allele 2 at the IL-1A+4845 and IL-1B+3954 loci to foretell which patients will develop severe chronic periodontitis. Therefore, clinicians must cautiously interpret results obtained with the commercially available genetic susceptibility test before they alter maintenance schedules or treatment regimens of symptomatic or asymptomatic patients.