Diagnostic accuracy of IgG 4/IgG and IgG 4 in patients with IgG 4-related disease: a meta-analysis.

Objective: This study aimed to evaluate and compare the diagnostic performance of immunoglobulin G4/Immunoglobulin G (IgG 4/IgG) and immunoglobulin G4 (IgG 4) alone in identifying immunoglobulin G4-related disease (IgG 4-RD).

Methods: A systematic review and meta-analysis were conducted using data from Medline, Embase, and the Cochrane Library from inception to November 2024. Two meta-analyses were performed to assess the diagnostic accuracies of IgG 4/IgG and IgG 4 in IgG 4-RD patients.

Results: Eight studies encompassing 754 IgG 4-RD patients and 9496 non-IgG 4-RD controls were included in the analysis. IgG 4/IgG demonstrated a sensitivity of 89% and a specificity of 91.6%, accurately detecting IgG 4-RD in 89% of cases and correctly identifying non-IgG 4-RD in 91.6% of cases. IgG 4 alone exhibited a higher sensitivity (94.9%) and a similar specificity (91%), indicating a slightly improved ability to identify IgG 4-RD cases. The positive likelihood ratio (PLR) and the negative likelihood ratio (NLR) for IgG 4/IgG were 7580 and 0.132, respectively, while IgG 4 alone had a PLR of 6403 and a lower NLR of 0.066, confirming the high diagnostic reliability. The diagnostic odds ratio (DOR) was 62.97 for IgG 4/IgG compared to 105.6 for IgG 4 alone, reflecting enhanced accuracy. The area under the curve (AUC) was 0.949 for IgG 4/IgG and 0.986 for IgG 4. The Q* index was 0.889 for IgG 4/IgG and 0.949 for IgG 4, further underscoring the diagnostic effectiveness of IgG 4 alone.

Conclusion: Both IgG 4/IgG and IgG 4 are highly accurate markers for diagnosing IgG 4-RD, with IgG 4 alone showing marginally higher sensitivity, DOR, and AUC. This suggests that IgG 4 alone may offer a slight advantage as a diagnostic marker for IgG 4-RD.