Performance of classification and diagnostic criteria for IgG4-related disease and comparison of patients with and without IgG4-related disease

Abstract

IgG4-related disease (IgG4-RD) was recently described in Japan. It is characterised by extensive organ involvement with tissue fibrosis. We assessed the performance of the 2019 American College of Rheumatology and European League Against Rheumatism (ACR/EULAR) classification criteria and the 2020 revised comprehensive diagnostic (RCD) criteria as well as differences between patients with and without IgG4-RD. In this retrospective, single-centre study of 50 patients admitted with suspected IgG4-RD, we evaluated the sensitivity and specificity of both criteria. We also compared clinical characteristics and laboratory data of patients with IgG4-RD (n = 42) and patients without IgG4-RD (n = 8). The ACR/EULAR classification criteria had 88.1% sensitivity and 87.5% specificity for IgG4-RD diagnosis. The RCD criteria had 100% sensitivity and 50% specificity. Patients with IgG4-RD had significantly more affected organs (p = 0.002). Patients with a single affected organ and IgG4-RD had significantly higher serum IgG4/IgG ratios (p = 0.027), lower serum C-reactive protein levels (p = 0.020), and lower total haemolytic complement activity (p = 0.044) than those without IgG4-RD. The ACR/EULAR classification criteria have high specificity and the RCD criteria have high sensitivity for diagnosing IgG4-RD. The number of affected organs is important for diagnosing IgG4-RD.

Figure 1

Affected organs by IgG4-RD status. (a) Number of patients by the number of affected organs. (b) Number of patients by affected organ. IgG4-RD immunoglobulin G4-related disease.

Figure 2

ROC curve for defining the optimal cut-off IgG4/IgG ratio in patients with a single affected organ. The ROC curve for distinguishing IgG4-RD from other diseases in patients with a single organ lesion. The cut-off value was 14.7%, AUC was 0.82, sensitivity was 90.9%, and specificity was 71.4%. AUC area under the curve, IgG4-RD immunoglobulin G4-related disease, ROC receiver operating characteristic.