Pleural effusion in patients with IgG4-related disease: Investigated features and compared to tuberculous pleurisy

Background and Aim: IgG4-related pleural effusion is rare and difficult to distinguish from tuberculous pleurisy because of its some similar findings including the high adenosine deaminase (ADA) in pleural effusion. Therefore, we aimed to demonstrate features of IgG4-related pleural effusion compared with tuberculous pleurisy. Methods: We retrospectively performed a chart review of hospitalized adult patients with IgG4-related pleural effusion and tuberculous pleurisy. The period of the study was from January 2017 to May 2019. Furthermore, we collected reports of IgG4-related pleural effusion using resources from PubMed and the Japan Medical Abstracts Society, and considered these reports and patients of our hospital together. We compared IgG4-related pleural effusion to tuberculous pleurisy. Results: We enrolled 19 patients with IgG4-related pleural effusion and 40 patients with tuberculous pleurisy. In laboratory findings of pleural effusion, patients with IgG4-related pleural effusion showed higher total protein (TP) and lower lactate dehydrogenase (LDH) and ADA than those with tuberculous pleurisy. We developed a prediction score which included TP ≥5.2 mg/dL, LDH ≤250 U/L, and ADA ≤60 U/L in laboratory findings of pleural effusion. The area under the curve of the score was 0.949 (95% confidence level: 0.905-0.993). Each variable was assigned a value of 1 point. When the cut-off value was 2 points, sensitivity and specificity were 87.5% and 100%. Conclusion: The study demonstrated that laboratory findings of pleural effusion could differentiate between IgG4-related pleural effusion and tuberculous pleurisy.