Abstract: Objective To examine levels of Plasma protease C1 inhibitor （SERPING1）of patients with latent autoimmune diabetes in adults（LADA）and explore their clinical significance. Methods The levels of SERPING1 in plasma were detected and compared among LADA, type 1 diabetes (T1DM), type 2 diabetes (T2DM) and healthy people. The correlation between the levels of SERPING1 in plasma and other clinical indicators such as age, disease course, glycosylated hemoglobin（HbA1c）, fasting blood glucose （FPG）, 2h postprandial plasma glucose（2hPG）, Fasting c-peptide（FCP）, 2h postprandial C peptide（2hCP）, and Glutamic Acid Decarboxylase Antibody（GADA）were analyzed. Multi-factor regression analysis and receiver operating characteristic (ROC) were used to evaluate the predictive effect of SERPING1 in LADA at the early stage. Results The level of SERPING1 in LADA was significantly higher than that in the other groups except T1DM（P＜0.05）. There was remarkable relation between SERPING1 and FCP、HbA1c、FPG、2hPG, while no significant correlation was found between SERPING1 and the other clinical indicators（P＞0.05）.FCP was involed in the regression equation（P＜0.05）,and it was the main influences on the levels of plasma SERPING1. ROC indicated that it would be not enough to estimate LADA by SERPING1 alone. SERPING1 along with other indicators would great improve the diagnostic efficiency. Conclusions SERPING1 along with other indicators will be useful for identifying LADA from T2DM at the early stage.

Key words: latent autoimmune diabetes in adults, Plasma protease C1 inhibitor, early prediction