Establishment of a serum IgG4 cut-off value for the differential diagnosis of IgG4-related disease in Chinese population

Advances in understanding and management of IgG4-related ophthalmic disease

Immunoglobulin G4-related ophthalmic disease (IgG4-ROD) is an emerging, immune-mediated fibroinflammatory orbital disease, characterized by tumefactive lesions with noticeable IgG4+ plasma cell infiltration and distinctive pathohistological features. This disease is often associated with elevated serum IgG4 concentrations. IgG4-ROD may affect any ophthalmic tissues, particularly the lacrimal gland, extraocular muscles, and trigeminal nerves. Although the exact pathogenic role of IgG4 antibodies remains unclear, B-cell depleting agents have been reported to be an effective treatment. The diverse clinical manifestations of IgG4-ROD complicate diagnosis, and without prompt treatment, visual-threatening complications such as optic neuropathy may arise. Recent advances in understanding and managing IgG4-ROD have revolutionized the diagnosis and treatment of this emerging disease. This review article aims to provide a comprehensive overview of the latest advancements in the field of IgG4-ROD.

The external validation of the 2019 ACR/EULAR classification criteria for IgG4-related disease in a large cohort from China

OBJECTIVE

To externally validate the performance of the 2019 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria for IgG4-related disease (IgG4-RD) within a cohort from China and to compare the criteria with the 2020 revised comprehensive diagnostic (RCD) criteria for IgG4-RD.

METHODS

This study included 875 IgG4-RD and 302 non-IgG4-RD cases (213 mimickers and 89 patients with other diseases). Using expert clinical judgment as the gold standard for diagnosis of IgG4-RD, the performance (sensitivity, specificity, area under the curve (AUC) of the 2019 ACR/EULAR criteria for IgG4-RD was evaluated. We also compared it with the 2020 RCD criteria.

RESULTS

The 2019 ACR/EULAR classification criteria had a sensitivity of 76.6% (95% CI: 73.8% to 79.4%) and a specificity of 98.0% (96.0%-99.4%), an AUC of 0.873 (0.857-0.889) in the overall cohort. Those false negative cases under the 2019 ACR/EULAR classification criteria had significantly lower levels of serum IgG4, and fewer had pathological information, with a higher frequency in the involvement of those uncommon organs compared with the true positive cases. The cases judged as negative by the 2019 ACR/EULAR classification criteria yet judged as "definite" by the 2020 RCD criteria had more involvement of uncommon organs.

CONCLUSIONS

The 2019 ACR/EULAR classification criteria for IgG4-RD show outstanding specificity and good sensitivity in real-world clinical practice. The 2020 RCD criteria are helpful for the diagnosis of IgG4-RD in clinical scenarios where IgG4-RD presents as involving an isolated organ, especially the unusual sites.

Clinical Utility of Personalized Serum IgG Subclass Ratios for the Differentiation of IgG4-Related Sclerosing Cholangitis (IgG4-SC) from Primary Sclerosing Cholangitis (PSC) and Cholangiocarcinoma (CCA)

Background: The differential diagnosis of immunoglobulin G4-sclerosing cholangitis (IgG4-SC) from primary sclerosing cholangitis (PSC) or cholangiocarcinoma (CCA) is important. In this study, we aimed to find the best combinations of serum IgG subclasses and IgG4 levels for differentiating IgG4-SC from PSC or CCA. Methods: In total, 31 patients with IgG4-SC, 27 patients with PSC, and 40 patients with CCA were enrolled from 2003 to 2017 at a single tertiary referral center. We retrospectively assessed the IgG4, IgG4/IgG1, IgG4/(IgG1+IgG3), and (IgG4+IgG2)/(IgG1+IgG3) in each of the patients. ROC curves were established to obtain the optimal cutoff value for each parameter. McNemar’s test was used to compare the sensitivities, specificities, and accuracies of diagnostic algorithms. Results: In differentiating IgG4-SC from PSC, the accuracies of IgG4/IgG1 ≥ 0.087 and of IgG4/(IgG1+IgG3) ≥ 0.081 were significantly higher than that of IgG4 ≥ 135 mg/dL alone (78% vs. 66%, p = 0.025). Serum IgG4 ≥ 52 mg/dL showed the best accuracy for differentiation of IgG4-SC from CCA, with a sensitivity and specificity of 80% and 82%, respectively, but this was statistically not significant (p = 0.405). Conclusions: The serum IgG4/IgG1 or IgG4/(IgG1+IgG3) level may help to differentiate IgG4-SC from PSC. IgG4 alone is the most accurate serologic marker for the differentiation of IgG4-SC from CCA.

A Unified Serum IgG4 Cutoff Level for the Diagnosis of IgG4-Related Disease Using a Wide Array of Kits

Objectives

An IgG4 level above 1350 mg/L is one of the comprehensive criteria for the diagnosis of IgG4-related disease (IgG4-RD). The purpose of this study was to evaluate the differences in IgG4 levels determined using reagents from two main manufacturers and their concordance with clinical diagnosis.

Methods

IgG4 levels were measured in 309 patients, including 146, 40, 42, 41, and 40 patients with untreated IgG4-RD, pancreatic cancer, primary Sjogren syndrome, systemic lupus erythematosus, and idiopathic retroperitoneal fibrosis, respectively, and 141 healthy controls. The results obtained using the Binding Site and Siemens reagents were compared in patients with IgG4-RD.

Results

The serum IgG4 level measured using the Siemens reagent was almost two times that measured using the Binding Site reagent. The rate of IgG4-negative patients, which was 19.9% based on measurement using the Binding Site reagent, was only 4.8% based on measurement using the Siemens reagent (P < 0.001).

Conclusions

There were significant differences in serum IgG4 levels based on commonly used reagents from different manufacturers. The IgG4 cutoff level of 1350 mg/L was not suitable for all detection reagents. Clinicians and patients should be cognizant of these differences associated with the specific detection reagents when evaluating the test results.

The Expression of IgG and IgG4 in Orbital MALT Lymphoma: The Similarities and Differences of IgG4-Related Diseases

Objective

This study aims to study the expression and role of IgG and IgG4 in orbital MALT lymphoma and to compare the characteristics of IgG4-related diseases.

Patients and Methods

Patients with orbital MALT lymphoma, treated in the West China Hospital of Sichuan University from 2012 to 2017, were enrolled in the current study. The immunological examination of the wax blocks of orbital masses was performed again and the expression level of IgG and IgG4 in pathological tissue was analyzed.

Results

The results presented that the positive rates of IgG and IgG4 in the cases of orbital MALT lymphoma were 90.91% and 61.98% respectively, of which IgG4/IgG >40% accounted for 49.33%. The positive rates of IgG and IgG4 in relapse cases were 94.60% and 70.27% respectively, and IgG4/IgG >40% accounted for 42.31%. There was no significant change in the expression of IgG and IgG4 in cases of lymphoproliferation converting to MALT lymphoma whereas, in cases of MALT lymphoma postoperatively converting to lymphoproliferation, there was an increase in IgG and IgG4 expression, with the change of IgG4 being significant.

Conclusion

IgG and IgG4 have a high correlation in the pathogenesis of MALT lymphoma and may even play an important role in the transformation of MALT lymphoma into orbital lymphoid hyperplasia. Given the association of IgG4 with inflammation and tumors and as an important diagnostic indicator for IgG4-RD and IgG4-related ophthalmic diseases, IgG4 may play an important role in these diseases.

Adult reference intervals for IgG subclasses with Siemens immunonephelometric assays in Chinese population

Objective

To determine the adult reference intervals for the Siemens IgG subclass reagents.

Methods

636 blood samples of healthy adults were analyzed to determine the level of IgG subclass using the reagents of Siemens immunonephelometric assay with molecular biology kits.

Results

IgGSc reference intervals were as follows: IgG1 4.45–9.76 g/L, IgG2 2.07–8.57 g/L, IgG3 0.08–0.80 g/L and IgG4 0.05–1.54 g/L. There was an excellent correlation between the total IgG and the sum of the IgG subclasses. No significant gender and age differences were observed.

Conclusions

Our data provide the missing reference intervals and enable the use of the nephelometric IgG subclass reagents in Chinese. The study can offer reference on clinic diagnose.

Immunoglobulin G4-related kidney disease: Pathogenesis, diagnosis, and treatment

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized clinical entity that often involves multiple organs; it is characterized by high levels of serum immunoglobulin G4 (IgG4), dense infiltration of IgG4+ cells, and storiform fibrosis. Cellular immunity, particularly T cell-mediated immunity, has been implicated in the pathogenesis of IgG4-RD. The most frequent renal manifestations of IgG4-RD are IgG4-related tubulointerstitial nephritis, membranous glomerulonephropathy (MGN), and obstructive nephropathy secondary to urinary tract obstruction due to IgG4-related retroperitoneal fibrosis, prostatitis, or ureter inflammation. Kidney function impairment can be acute or chronic. In IgG4-MGN, proteinuria can be in the nephrotic range. The diagnosis of IgG4-related kidney disease should not be based solely on serum IgG4 levels or the number of tissue-infiltrating IgG4+ plasma cells. Diagnosis should be based on specific histopathological findings, confirmed by tissue immunostaining and an appropriate clinical context. Steroid treatment is the first-line therapy. For relapsing or refractory cases, immunosuppressants could be combined with steroids. In hydronephrosis patients, appropriate immunosuppressive therapy could preclude the implantation of a double J ureteral catheter.

Immunoglobulin-G4 related mastitis: A case report

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IgG4-RM is exceedingly rare with only ten reported cases in the literatreu.

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Diagnosis of IgG4-RM is based exclusively on histological analysis.

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It is a benign chronic inflammatory process that can be treated sufficiently with excision or steroid.

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Extensive whole body imaging is generally not recommended unless the patient is symptomatic.

Introduction

IgG4-related mastitis (IgG4-RM) is exceedingly rare with only ten cases reported in the literature to date. Organs that are affected with IgG4-related disease (IgG4-RD) all share the same histopathological hallmarks consisting of dense lymphocytic infiltration, storiform fibrosis and obliterative phlebitis.

Presentation of case

This case report highlights a case of IgG4-RM found incidentally in a 52-year-old woman during a routine breast screen and it explores the current literature about IgG4-RM and IgG4-RD.

Discussion

IgG4-RM and IgG4-RD, in general, is a new entity in the field of medicine and its aetiology is not well understood. In the literature, IgG4-RM often presents as a painless palpable breast lump in isolation or with other systemic manifestations. IgG4-RM is considered benign and has excellent prognosis post-conservative treatment with steroid or surgical excision.

Conclusion

IgG4-RM is diagnosed exclusively on histological analysis. It is hard to distinguish IgG4-RD from malignant breast lesions purely on clinical examination and imaging studies. Increasing awareness of this condition among clinicians will assist them in managing patients better. Extensive whole body imaging is not recommended unless symptomatic.

Diagnostic performances of serum IgG4 concentration and IgG4/IgG ratio in IgG4-related disease

Patients with IgG4-related disease (IgG4-RD) often have elevated serum IgG4 levels. Here, we aimed to evaluate the diagnostic performances of elevated serum IgG4 concentration and IgG4/IgG ratio for IgG4-RD. We retrospectively analyzed 1381 patients subjected to serum IgG subclass testing to differentiate IgG4-RD from other diseases at Peking University People's Hospital from 2012 to 2016. This sample included 133 IgG4-RD patients and 1248 non-IgG4-RD patients. Serum IgG subclass concentrations were measured using Siemens reagents. The median values (25th-75th percentile) for serum IgG4 concentration and IgG4/IgG ratio, respectively, were 8640 (3970-17750) mg/L and 0.339 (0.229-0.517) in IgG4-RD patients and 450 (220-920) mg/L and 0.032 (0.014-0.061) in non-IgG4-RD patients (p < 0.001). For distinguishing IgG4-RD from non-IgG4-RD, the optimal cut-off values of IgG4 and IgG4/IgG were 2100 mg/L and 0.114, respectively. The corresponding area under the curve (AUC) values were 0.964 and 0.970, respectively. Comparison of the receiver operating characteristic curves revealed a significant difference between these AUC values (p = 0.002). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), respectively, were 94.7, 91.6, 54.5, and 99.4% for the IgG4 optimal cut-off value and 96.2, 92.1, 56.4, and 99.6% for the IgG4/IgG optimal cut-off value. Our results confirmed that elevated serum IgG4 concentration and IgG4/IgG ratio were of great value for IgG4-RD diagnosis.

Diagnostic Value of Serum IgG4 for IgG4-Related Disease: A PRISMA-compliant Systematic Review and Meta-analysis

Many studies about serum IgG4 for the diagnosis of IgG4-related disease (IgG4-RD) have been reported. However, these studies had relatively small sample sizes and the diagnostic accuracy values varied much between them.The aim of this study was to perform a meta-analysis to evaluate the diagnostic value of serum IgG4 for IgG4-RD.We conducted a search of relevant articles using MEDLINE, EMBASE, Web of Science, SCOPUS, and Cochrane Library databases published before December 2015.Studies those assessed the diagnostic accuracy of serum IgG4 for IgG4-RD and those provided the cut-off value for serum IgG4 were included.Data were synthesized using the random-effect model. Statistical analysis was performed using STATA with the MIDAS module and Meta-DiSc 1.4 software.A total of 9 case-control studies were analyzed, which included 1235 patients with IgG4-RD and 5696 overall controls. The pooled estimate, for a cut-off value ranged from 135 to 144 mg/dL, produced a sensitivity of 87.2% (95% CI, 85.2-89.0%) and a specificity of 82.6% (95% CI, 81.6-83.6%). The positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were 6.48 (95% CI, 3.98-10.57), 0.14 (95% CI, 0.09-0.21), and 45.15 (95% CI, 23.41-87.06), respectively. The area under the curve (AUC) of the summary receiver operating characteristic curve (SROC) was 0.94 (0.92-0.96). When a cut-off value of 2-fold the upper limit of normal was used (ranged from 270 to 280 mg/dL), the pooled sensitivity was 63% (95% CI, 60.0-66.0%), and the specificity was 94.8% (95% CI, 94.1-95.4%). The PLR, NLR, and DOR were 13.3 (95% CI, 7.39-24.0), 0.41 (95% CI, 0.29-0.58) and 33.42 (95% CI, 13.88-80.43), respectively. The AUC of the SROC was 0.92 (0.90-0.94).Only a relatively small number of studies were included, and significant heterogeneity was observed in this meta-analysis.Serum IgG4 is a modestly effective marker to diagnose IgG4-RD. Doubling the cut-off value for IgG4 could not improve the overall test characteristics. A high specificity inevitably accompanies with a significant sacrifice in sensitivity.