Immunoglobulin subclass 4 for the diagnosis of immunoglobulin subclass 4-associated diseases in an unselected liver and pancreas clinic population

Early Cardiovascular Disease After the Diagnosis of Systemic Sclerosis

PURPOSE

The purpose of this study is to assess risk and time trends of newly recorded myocardial infarction and stroke in cases with systemic sclerosis.

METHODS

We conducted a matched incident cohort study (1996-2010) among patients satisfying at least one of the following: 1) diagnosis of systemic sclerosis on at least 2 visits within a 2-year period by a nonrheumatologist physician; or 2) diagnosis of systemic sclerosis on at least one visit by a rheumatologist or from hospitalization; as well as receiving no prior systemic sclerosis diagnosis between 1990 and 1995. Ten controls were matched by birth year, sex, and calendar year of exposure from the general population for each case. Incident myocardial infarction, stroke, and myocardial infarction or stroke was recorded from hospital or death certificates. We estimated incidence rate ratios and hazard ratios (HRs) after adjusting for confounders.

RESULTS

Among 1239 individuals with systemic sclerosis and no history of myocardial infarction (83% female, 56 years old), the incidence rate for myocardial infarction was 13.0/1000 person-years vs 4.1/1000 person-years in the comparison cohort. The incidence rate for stroke was 8.0/1000 person-years vs 3.7/1000 among controls. The adjusted HRs were 3.49 (95% confidence interval [CI], 2.52-4.83) and 2.35 (95% CI, 1.59-3.48) for myocardial infarction and stroke, respectively. For myocardial infarction and stroke, the risk was highest within the first year following diagnosis (HR 8.95; 95% CI, 5.43-14.74 and HR 5.25; 95% CI, 2.90-9.53, respectively).

CONCLUSION

This large general population-based study indicates an increased risk of myocardial infarction and stroke in patients with systemic sclerosis, especially within the first year of diagnosis.

Detection of serum IgG4 levels in patients with IgG4-related disease and other disorders

Objective

Elevated serum IgG4 levels are an important hallmark for diagnosing IgG4-related disease (IgG4-RD), but can also be observed in other diseases. This study aimed to compare two different testing methods for IgG4: ELISA and nephelometric assay. Both assays were used to measure serum IgG4 concentrations, and to assess the prevalence of high serum IgG4 levels in both IgG4-RD and non-IgG4-RD diseases.

Methods

A total of 80 serum samples were tested using the nephelometric assay and ELISA method that we established. Serum IgG4 concentrations were determined by ELISA for 957 patients with distinct diseases, including 12 cases of IgG4-RD and 945 cases of non-IgG4-RD.

Results

IgG4 levels from 80 selected serum samples examined by ELISA were in agreement with those detected using the nephelometry assay. Meanwhile, the serum IgG4 concentrations measured by ELISA were also consistent with the clinical diagnoses of patients with IgG4-RD during the course of disease. The Elevated levels of serum IgG4 (>1.35 g/L) were detected in all IgG4-RD (12/12) patients, and the prevalence of high IgG4 serum levels was 3.39% in non-IgG4-RD cases. Among them, the positive rates of serum IgG4 were 2.06% in patients with carcinoma and 6.3% in patients with other non-IgG4 autoimmune diseases.

Conclusion

Our established ELISA method is a reliable and convenient technique, which could be extensively used in the clinic to measure serum IgG4 levels. High levels of IgG4 were observed in IgG4-RD. However, this phenomenon could also be observed in other diseases, such as carcinomas and other autoimmune diseases. Thus, a diagnosis of IgG4 disease cannot only be dependent on the detection of elevated serum IgG4 levels.

Pathologies Associated with Serum IgG4 Elevation

Statement of Purpose. IgG4-related disease (IgG4-RD) is usually associated to an increase of serum IgG4 levels. However other conditions have also been associated to high serum IgG4 levels. Methods. All IgG subclasses analyses performed in our hospital over a one-year period were analyzed. When IgG4 level were over 1.35 g/L, the patient's clinical observation was analyzed and both final diagnosis and reason leading to IgG subclasses analysis were recorded. Only polyclonal increases of IgG4 were considered. Summary of the Results. On 646 IgG subclass analysis performed, 59 patients had serum IgG4 over 1.35 g/L. The final diagnosis associated to serum IgG4 increase was very variable. Most patients (25%) presented with repeated infections, 13.5% with autoimmune diseases, and 10% with IgG4-RD. Other patients presented with cancer, primary immune deficiencies, idiopathic interstitial lung disease, cystic fibrosis, histiocytosis, or systemic vasculitis and 13.5% presented with various pathologies or no diagnosis. Mean IgG4 levels and IgG4/IgG ratio were higher in IgG4-RD than in other pathologies associated to elevated IgG4 levels. Conclusions. Our study confirms that elevation of serum IgG4 is not specific to IgG4-RD. Before retaining IgG4-RD diagnosis in cases of serum IgG4 above 1.35 g/L, several other pathological conditions should be excluded.