Relationship between clinical predictors and tubulointerstitial damage in adult-onset primary nephrotic syndrome.

Background: Tubulointerstitial damage (TID) is an important mediator in the progression of chronic proteinuric nephropathies. Our aim in this study was to evaluate the relationship between several clinical predictors and TID in adult-onset primary nephrotic syndrome in China.

Methods: One hundred ninety-five adult inpatients who were diagnosed with primary nephrotic syndrome based on clinical presentation and biopsy results were enrolled in this study from March 2003 to September 2005. The degree of TID was graded by a semiquantitative method including <2 score and >or=2 score.

Results: In all patients, the rate of glomerulosclerosis was correlated with the severity of TID. Serum creatinine and uric acid (r = 0.183, p = 0.012 and r = 0.377, p = 0.00001, respectively) but not serum lipid or total 24-h urinary protein were related with TID. In 64 patients, urinary excretion of IgG (r = 0.443, p = 0.00001) but not of albumin, transferrin, retinal-binding protein, or alpha1-microglobulin were significantly associated with the extent of TID. Proteinuria selectivity index based upon IgG also correlated significantly with the extent of TID (p = 0.0001) (score 0-1 vs. score >or=2).

Conclusions: These results showed that serum creatinine and uric acid, the excretion of urinary IgG and proteinuria selectivity index based upon IgG, were highly correlated with the severity of TID in adult-onset primary nephrotic syndrome. These clinical parameters might be useful for predicting the development and progression of proteinuric nephropathy as independent risk factors.