Kidney Week

Abstract: SA-PO413

A Novel Equation Using Low-Invasive Test Items to Estimate the Severity of Interstitial Fibrosis in IgA Nephropathy

Session Information

• CKD: Estimating Equations, Incidence, Prevalence, Special Populations
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Chronic Kidney Disease (Non-Dialysis)

• 302 CKD: Estimating Equations, Incidence, Prevalence, Special Populations

Authors

• Inui, Keita, Shinshu University , Matsumoto, Japan

Keita Inui,

• Yamaka, Kosuke, Shinshu University , Matsumoto, Japan

Kosuke Yamaka,

• Yamada, Yosuke, Shinshu University , Matsumoto, Japan

Yosuke Yamada,

• Kamijo, Yuji, Shinshu University School of Medicine, Matsumoto, Japan

Yuji Kamijo,

Background

In IgA nephropathy, tubulointerstitial fibrosis is said to be very important in predicting whether or not renal dysfunction is progressive. Until now, however, invasive renal biopsy has been the primary means of determining the severity of fibrosis in IgA nephropathy. A formula to estimate tubulointerstitial fibrosis severity using such low-invasive parameters as physical findings, serology, and urinalysis is therefore needed.

Methods

Masson Trichrome-stained renal biopsy specimens of 51 patients diagnosed as having IgA nephropathy at Shinshu University Hospital were collected. The severity of interstitial fibrosis as calculated by the percentage of area stained blue in the cortex tubulointerstitium (Fib%) was quantitatively measured by ImageJ analysis software (Figure) and its correlation with various factors was examined. A formula for estimating interstitial fibrosis was then derived by multiple regression analysis using parameters whose correlation with Fib% was strong.

Results

Fib% increased proportionally to Oxford classification T-score (P<0.001) and accurately reflected the severity of interstitial fibrosis. Fib% also correlated strongly with serum creatinine (sCre) (mg/dL) (correlation coefficient [R]: 0.61; P<0.01), urinary N-acetyl-β-D-glucosaminidase (uNAG) (U/gCre) (R: 0.44; P<0.01), and body mass index (BMI) (kg/m²) (R: 0.44; P<0.01). The estimation formula of Fib% from these 3 parameters was determined as: Fib% = 16.84 + 17.71(sCre) + 0.51(BMI) + 0.59(uNAG) (coefficient of determination: 0.53; P<0.01).

Conclusion

Interstitial fibrosis in IgA nephropathy can be estimated using data obtained from low-invasive tests. A prospective study is being planned to validate our novel formula.