Clinical Performance of Immunonephelometric Assay and Chemiluminescent Immunoassay for Detection of IgG Subclasses in Chinese

Abstract

Background: Detection of IgG subclasses (IgGSc) is vital for the diagnosis and management of disease, especially IgG4-related diseases (IgG4-RD). This study aimed to evaluate the performances of the chemiluminescent immunoassay (CLIA) for detecting IgGSc and diagnosing IgG4-RD by IgGSc.

Methods: A total of 40 individuals with IgG4-RD, 40 with primary Sjogren's syndrome (pSS), and 40 healthy controls (HCs) were enrolled. Serum samples were collected for the simultaneous detection of IgG1, IgG2, IgG3, and IgG4 by the Siemens immunonephelometric assay and the CLIA. The correlation analysis was performed, and diagnostic value was analyzed by the receiver operating characteristic (ROC) curve.

Results: Patients with IgG4-RD had higher IgG4 (p < 0.001) and lower IgG1 (p < 0.001) than those with pSS, and HC. The results by the Siemens immunonephelometric assay and the CLIA showed a strong correlation in detecting IgG1, IgG2, IgG3, and IgG4 (r = 0.937, r = 0.847, r = 0.871, r = 0.990, all p < 0.001, respectively). The sum of IgG1, IgG2, IgG3, and IgG4 using two assays strongly correlated with total IgG by the IMMAGE 800 (r = 0.866, r = 0.811, both p < 0.001, respectively). For discriminating IgG4-RD from pSS and HC, no significant differences were observed in CLIA IgG4 and Siemens immunonephelometric assay IgG4 (z = 0.138, p = 0.891), which provided the area under the curves (AUCs) of 0.951 (p < 0.001) and 0.950 (p < 0.001), respectively. The AUCs of CLIA IgG1 and Siemens immunonephelometric assay IgG1 in distinguishing pSS from IgG4-RD and HC were 0.761 (p < 0.001) and 0.765 (p < 0.001), respectively, with no significant differences (z = 0.228, p = 0.820).

Conclusions: The CLIA and the Siemens immunonephelometric assay appeared to have good consistency with comparable diagnostic value in detecting IgGSc, especially IgG4, and IgG1 that can accurately identify IgG4-RD or pSS in clinical practice.

Keywords: IgG subclasses; IgG4‐related diseases; chemiluminescent immunoassay; immunonephelometric assay; primary Sjogren's syndrome.

FIGURE 1

Serum levels of IgG subclass in patients with IgG4‐RD and pSS measured by the Siemens assay and CLIA. IgG subclasses measured using the (a) CLIA (b) and the Siemens BN P. Data were presented as median (Q25, Q75) and were analyzed by the Kruskal–Wallis test. *p < 0.05, **p < 0.01, ***p < 0.001.

FIGURE 2

Correlation of serum IgG subclasses levels detected by the Siemens BN P to those by the CLIA. Correlation of serum IgG1 (a), IgG2 (b), IgG3 (c), IgG4 (d), and the sum of IgG1, IgG2, IgG3, and IgG4 (e) detected by the Siemens BN P to those by the CLIA. Data were analyzed by Spearman's rank correlation.

FIGURE 3

Comparison of the positive rate of IgG subclasses measured by the Siemens BN P and the CLIA in different cohorts. The positive rate of IgG subclasses in patients with (a) IgG4‐RD and (b) pSS. The positive rate of IgG subclasses (c) in the HC group and (d) in all individuals. Data were analyzed by the chi‐squared test. NS: p > 0.05.

FIGURE 4

Relationships between the sum of IgG1, IgG2, IgG3, and IgG4 and the total serum IgG measured by the Beckman Coulter IMMAGE 800 in patients with IgG4‐RD and pSS. Relationship between the serum total IgG and the sum of IgG subclasses measured using the (a) CLIA and (b) Siemens BN P.

FIGURE 5

Receiver operating characteristic curve (ROC) analysis of the serum levels of IgG subclasses. (a) ROC of IgG4 levels to distinguish patients with IgG4‐RD from those with (a) pSS and HCs, (b) pSS. (c) ROCs of IgG1, IgG3, and IgG4 to distinguish patients with IgG4‐RD patients from those with HCs.

FIGURE 6

ROC analysis of the serum levels of IgG subclasses. (a) ROCs of IgG1 and IgG4 to distinguish patients with pSS from those with IgG4‐RD and HCs. (b) ROCs of IgG1 and IgG3 to distinguish patients with pSS from those with HC.