Direct immunofluorescence of labial gland in diagnosis of Sjogren's disease.

OBJECTIVE: To investigate the expression of IgG, IgA, IgM, C3, and C1q in labial gland tissue using direct immunofluorescence (DIF) in patients with Sjogren's disease (SjD), and to explore the diagnostic role of labial gland DIF in SjD, as well as its differential diagnosis when SjD occurs in combined association with systemic lupus erythematosus (SjD + SLE) and undifferentiated connective tissue disease (UCTD). METHODS: General clinical data and labial gland specimens of 65 clinically suspected SjD patients treated at the Third Affiliated Hospital of Guangzhou Medical University were collected. DIF detection of IgG, IgA, IgM, C3, and C1q in the labial gland was performed with frozen sections. The expression characteristics in healthy controls (HC, n = 10), UCTD (n = 10), SjD (n = 34), and SLE + SjD (n = 11) and the diagnostic role in SjD were analyzed. RESULTS: Compared to HC, UCTD patients had higher expression rates of IgA (p < 0.05), SjD patients had higher expression rates of IgG, IgA, and IgM (p < 0.01), while SLE + SjD patients had higher IgG, IgM, and C3 expression rates (p < 0.05). Compared to SjD, SLE + SjD patients had increased C3 and C1q expression rates (p < 0.01). In the SjD group, the DIF expression positivity rates of IgG and IgA showed statistically significant differences between the treated and untreated groups (p < 0.05). The sensitivities of IgG and IgM for diagnosing SjD were 86% and 82%, respectively, with both specificities at 100%. Combined IgG and IgM diagnosis had a sensitivity of 100% and specificity of 100%. CONCLUSION: IgG, IgA, and IgM deposition is evident in SjD labial glands. Treatment reduces IgG and IgA deposition, and DIF can improve the sensitivity of labial gland biopsy. C3 and/or C1q deposition in labial gland DIF indicates a potential tendency to develop SLE. Key Points CurrAQently, the DIF expression of IgG, IgA, IgM, C3, and C1q in the labial gland tissue of SjD patients, and its diagnostic and differential diagnostic value for SjD, as well as its predictive value for the differentiation of UCTD, are unclear. This study found that the combined detection of IgG and IgM has a sensitivity of 100% and a specificity of 100% for diagnosing SjD. The deposition of C3 and/or C1q in labial gland DIF suggests a potential tendency for patients to develop SLE. Conducting DIF testing can improve the sensitivity and specificity of labial gland biopsy in diagnosing SjD and provide new evidence for differential diagnosis and predicting UCTD differentiation.