Treatment outcome for IDDM patients in relation to glutamic acid decarboxylase autoantibodies and serum IgG to periodontal pathogens

Background: Patients with insulin-dependent diabetes mellitus (IDDM) have e levated risk for periodontitis (PD) relative to subjects without diabetes. Whether refractory PD in IDDM patients is related to autoimmunity as indica ted by serum glutamic acid decarboxylase autoantibody GAD Ab levels or to h ost bacterial immunity as reflected by serum antibody titers to periodontal pathogens is unknown. Aims: To determine if non-surgical periodontal treatment outcome differs be tween GAD Ab-seropositive and -seronegative IDDM patients by assessing the following parameters: (1) pretreatment serum levels of GAD Ab, (2) pretreat ment serum Ige titers to key periodontal pathogens, and (3) changes in peri odontal pocket probing depth (PDC) after treatment. Methods: Before and two months after periodontal treatment of Il GAD Absero negative and 7 -seropositive subjects, PDC was assessed and serum GAD Ab an d IgG to Porphyromonas gingivalis (Pg), Bacteroides forsythus (Bf), and Act inobacillus actinomycetemcomitans (Aa) were studied using established radio ligand precipitation and enzyme-linked immunosorbent assays, respectively. Results: The PDC decrease was significantly better for GAD Ab-seronegative subjects than for seropositive subjects (median 1.4 mm +/-0.5 s.d versus 0. 5 mm +/-0.3 s.d., p <0.03, Mann-Whitney). GAD Ab levels and PDC were positi vely correlated (r=+0.71, p <0.05) for sere-positive subjects but were neut ral (r=-0.07) for seronegative subjects. Serum IgG to Pg and GAD Ab levels were positively associated (r(2)=0.42) in seropositive subjects. Logistic r egression analysis confirmed that GAD Ab status was the primary discriminat or for PDC (p <0.04). Conclusion: Detection of elevated GAD Ab levels in combination with elevate d Ige titers to Pg before treatment is indicative of IDDM patients with ref ractory PD.