To investigate the role of urinary β2-microglobulin (β2-MG) in evaluating the prognosis of patients with primary membranous nephropathy (PMN).

A retrospective analysis was conducted in 66 patients with PMN who were first admitted to the Fuyang Hospital Affiliated to Anhui Medical University from December 2018 to November 2023. According to their urinary β2-MG levels, they were divided into a high β2-MG group (40 cases) and a low β2-MG group (26 cases). The general information, laboratory indicators, and renal biopsy pathology results of the patients were collected. Logistic regression method was applied to analyze the related influencing factors of urinary β2-MG. And the prognostic role of urinary β2-MG in the patients was analyzed with the receiver operating characteristic (ROC) curve.

At the first admission, compared with the low β2-MG group, the high β2-MG group showed higher levels of mean arterial pressure, serum creatinine, 24-hour urinary protein, anti-phospholipase A2 receptor antibody, and renal interstitial lesion score, but showed lower level of eGFR (all P<0.05). Multivariate analysis showed that eGFR, 24-hour urinary protein, anti-phospholipase A2 receptor antibody, and renal interstitial lesion score were independent risk factors for the high level of urinary β2-MG. Compared with data at the first admission, the levels of serum creatinine, 24-hour urinary protein, and anti-phospholipase A2 receptor antibody in the high β2-MG group at the last follow-up were significantly higher, while eGFR was lower (all P<0.05). And the indicators were also statistically different between the two groups (all P<0.05). Compared with the low β2-MG group, the high β2-MG group had a higher incidence of poor prognosis (P<0.05). The ROC curve analysis showed that the optimal cutoff value for urinary β2-MG was 0.303 mg/L, and the area under the curve was 0.875, with the sensitivity being 93.7% and the specificity being 76.9%.

Anti-phospholipase A2 receptor antibody, eGFR, 24 h urinary protein, and renal interstitial lesion score were independent risk factors for high urinary β2-MG, and patients with high urinary β2-MG had poor prognosis. Urinary β2-MG level might be used for predicting the prognosis of PMN patients, which may be of value for reference during the immunosuppressive therapy.