Value of serum IgG4 and IgG4/IgG ratio in differential diagnosis of autoimmune diseases / 中国基层医药

ABSTRACT

Objective:To investigate the value of immunoglobulin G4 (IgG4) and IgG4/ immunoglobulin G (IgG) ratio in the differential diagnosis of IgG4-related diseases (IgG4-RD) and other autoimmune diseases.Methods:A total of 35 patients with IgG4-RD and 937 patients with autoimmune diseases who received treatment in Beijing Hospital from January 2021 to July 2022, and 200 subjects who concurrently underwent health checkups in the same hospital were included in this study. The IMMAGE 800 and BN II automatic special protein analyzers were used to detect IgG and IgG4. The receiver operating characteristic (ROC) curve of IgG4 and IgG4/IgG ratio was plotted.Results:Serum IgG4 level and IgG4/IgG ratio in the IgG4-RD group were 2.83 (2.01, 5.07) g/L and 25% (18%, 43%) respectively, which were higher than 0.35 (0.16, 0.72) g/L, 3% (1%, 6%) in the autoimmune disease group and 0.27 (0.14, 0.49) g/L, 2% (1%, 4%) in the healthy control group ( U = 795.50, 82.50, 1 744.50, 205.50, all P < 0.001). Taking IgG4 ≥ 1.35 g/L as the standard, patients with IgG4 ≥ 1.35 g/L in the three groups were screened out. There was a statistically significant difference in IgG4/IgG ratio between the IgG4-RD group and the non-IgG4-RD group ( U = 453.50, P < 0.001). The ROC curve of IgG4 and IgG4/IgG ratio showed that when IgG4 was 1.47 g/L, the sensitivity was 91.7%, the specificity was 83.5%, and the area under the ROC curve was 0.96. When IgG4/IgG was 12.5%, the sensitivity was 91.4%, the specificity was 85%, and the area under the ROC curve was 0.96. Taking IgG4 ≥ 1.47 g/L and IgG4/IgG ≥ 12.5% as the diagnostic criteria of IgG4-RD, the sensitivity was 94.3%, the specificity was 85.9%, and the area under the ROC curve was 0.96, which were higher than the sensitivity (87.2%) and diagnostic specificity (82.6%) provided by IgG4 alone. Conclusion:Because non-IgG4-RD diseases can also have the phenomenon of increased IgG4, when IgG4 ≥ 1.47 g/L is taken as the diagnostic criteria, its diagnostic sensitivity and specificity are the highest. Combined detection of IgG4 and IgG4/IgG ratio can increase the diagnostic efficacy of IgG4-RD.