[Changes and clinical significance of serum proteinase 3 in latent autoimmune diabetes in adults].

Objective: To investigate the changes of circulating proteinase 3 (PR3) in latent autoimmune diabetes mellitus in adults (LADA) patients, type 2 diabetes mellitus (T2DM) patients, obese patients without diabetes and healthy controls, and explore the value of serum PR3 in differentiating LADA and T2DM. Methods: Forty LADA patients, 29 T2DM patients, 26 obesity patients without diabetes, and 76 healthy controls were enrolled in Department of Metabolism & Endocrinology, the Second Xiangya Hospital, Central South University. Serum PR3 was detected by enzyme-linked immunosorbent assay (ELISA). The differences of serum PR3 among the four groups were compared. The correlation between serum PR3 and other metabolic indexes was analyzed. The value of serum PR3 in the differential diagnosis between LADA and T2DM was evaluated. Results: There was no significant difference in age among LADA patients, T2DM patients, obesity patients without diabetes and healthy controls [(50±13) years, (49±6) years, (49±6) years vs (47±7) years, P=0.254], while there was significant difference in gender among the four groups (χ(2)=18.28, P<0.001). Serum PR3 was significantly increased in LADA patients compared to the other three groups [195.4 (127.6, 288.1) μg/L vs 43.4 (30.9, 53.7) μg/L, 36.0 (29.2, 46.4) μg/L, 41.2 (30.2, 52.8) μg/L, all P<0.01], whereas there was no significant differences among the other three groups. After adjustment for age, gender and body mass index (BMI), serum PR3 remained higher in LADA patients compared to the other three groups. Correlation analysis indicated that PR3 correlated positively with fasting and 2-hour postprandial blood glucose (r=0.346, r=0.357, both P<0.001). Receiver operating characteristic (ROC) curve showed that the cut-off value of PR3 (71.7 μg/L) for differentiating LADA and T2DM had a sensitivity of 97.5% and specificity of 89.7% and rendered an area under the curve of 0.955 (95%CI: 0.894~1.000, compared to 0.5, P<0.01). Conclusion: Serum PR3 significantly elevated in LADA patients, and may serve as a biomarker for differentiating LADA and T2DM patients.