Normal value of urinary immunoglobulin G

Urinary immunoglobulin G (IgG) is the most abundant serum immunoglobulin secreted by the adrenal cortex and is primarily involved in serum antibody immune responses. Under normal circumstances, the reference range for urinary IgG concentration in adults is 0–15 mg/dL; in children, the normal range is 0–5 mg/dL, which may be largely attributed to children's relatively weaker defense mechanisms against foreign substances. Normally, urinary IgG levels are much lower than serum IgG levels. Elevated urinary IgG concentrations occur only under conditions of visceral lesions, inflammation, or active immune responses. Increased urinary IgG may indicate the following diseases: ① renal tuberculosis; ② bacterial infections; ③ glomerulonephritis; ④ chronic nephritis; ⑤ atrophic kidney disease; ⑥ kidney transplantation; ⑦ renal vasculitis; ⑧ multiple sclerosis, among others. Clinically, urinary IgG testing is useful for monitoring the ongoing activity of foreign antigens or immune-related diseases and assessing renal function. Typically, urinary IgG levels can return to the normal range during treatment. Therefore, regular monitoring of urinary IgG is important for effectively managing pharmacological therapy in patients.