Predictive value of interstitial inflammation for renal outcome in patients with immunoglobulin a nephropathy

Renal interstitial inflammation (RII) is a common pathological feature in immunoglobulin A nephropathy (IgAN) and may predict renal outcomes, but further validation is required. This study evaluated the prognostic value of RII and inflammatory cell infiltration in patients with IgAN.

This retrospective cohort study included adults with biopsy-confirmed IgAN. Renal interstitial inflammation was categorised as 0 (absent), 1 (around atrophic tubules) or 2 (beyond atrophic tubules). Interstitial CD3⁺, CD20⁺ and CD68⁺ cells were quantified via immunohistochemistry. The primary outcome was a composite of a ≥ 40 % decline in the estimated glomerular filtration rate or end-stage renal disease.

Of the 112 participating patients, 30 (26.8 %) experienced the primary outcome. A higher RII score was associated with increased risk of progression (hazard ratio for score 2 vs 0: 4.73, 95 % confidence interval [CI]: 2.01-11.13, p = 0.001). Patients with the outcome had higher densities of interstitial CD3⁺, CD20⁺ and CD68⁺ cells at biopsy. Kaplan-Meier analysis showed lower renal survival in patients with higher inflammatory cell densities (p < 0.05). The RII score alone had an area under the curve of 0.804 (95 % CI: 0.715-0.894) for predicting progression, which improved to 0.865 (95 % CI: 0.779-0.951) when combined with the Oxford classification score.

The severity of RII is independently associated with renal prognosis in IgAN. Immunohistochemical evaluation of inflammatory cell infiltration may improve risk stratification and guide early intervention.