Association between Infection and Calculated Globulin Level among Patients with Thymic Epithelial Tumor

Background: Thymic epithelial tumors (TETs) are uncommon malignancies uniquely associated with autoimmunity and immunodeficiency. Previous studies among patients with primary immunodeficiency diseases have shown that a low calculated globulin (CG) level, obtained by subtracting albumin from total protein level, is associated with infection risk. We investigated this association among patients with TET. Methods: A cross-sectional retrospective study was performed based on electronic medical records of patients with TET treated during 2002-2024 at a tertiary care institution. For each patient, their lowest CG level and the date of occurrence were identified. The incidence of serious infection requiring hospitalization during 6 months before and 6 months after the index date was recorded. Multivariable Poisson regression models were constructed. Results: Among 101 TET patients, 96 patients (95%) had the information available to derive at least one CG level. The median lowest CG level was 2.65 g/dL (range 1.0-4.2). There were 33 serious infection episodes. Pneumonia was the most prevalent type of infection in 52% of episodes. In a multivariable analysis, a CG level below 2.0 was independently associated with the prevalence of infection with a prevalence ratio of 6.18 (95% CI: 3.12-12.23, p < 0.001). Furthermore, thymectomy was significantly associated with infection. Conclusions: Among patients with TET, a low CG level was associated with an increased prevalence of serious infections. Our limited experiences suggest that it is feasible to derive the CG level for most patients during routine clinical care.