MO638ANEMIA IN DIABETIC PATIENTS REFLECTS SEVERE TUBULOINTERSTITIAL INJURY AND ASSISTS CLINICALLY IN PREDICTING DIAGNOSIS OF DIABETIC NEPHROPATHY
Authors: Yokota Soichiro , Ito Kenji , Watanabe Maho , Takahashi Koji , Himuro Naoko , Yasuno Tetsuhiko , Miyake Katsuhisa , Masutani Kosuke , Nakashima Hitoshi , Inoue Yori , Uesugi Noriko 
Published: May 2021

Abstract

Background and Aims
Diabetic nephropathy (DN) is currently a leading cause of end-stage kidney disease worldwide. Kidney biopsy is generally performed in diabetic patients to discriminate between DN and non-diabetic kidney disease (NDKD), and to provide more specific treatments. In addition to conventional predicting factors of DN, recent studies suggested the predictive value of anemia in the diagnosis of DN, however detailed pathophysiology and the significance of anemia in renal pathology are not fully understood. This study aimed to investigate the impact of anemia on renal pathology and clinical course in patients who underwent kidney biopsy.

Method
We reviewed 81 patients (60.4 ± 13.7 years, 54 men and 27 women) with type 2 diabetes who underwent percutaneous kidney biopsy in Fukuoka University Hospital from January 2001 through March 2020. DN was diagnosed by mesangial expansion or nodular glomerulosclerosis observed under a light microscope, and immunofluorescence assisted in differentiating NDKD from DN. Anemia was defined as hemoglobin level &lt;13 g/dL in males and &lt;12 g/dL in females in accordance with the World Health Organization standards. Laboratory and pathological findings, and clinical courses were investigated.

Results
According to their pathological findings, patients were classified into two groups: isolated DN (DN group, n=30) and NDKD alone or concurrent DN (NDKD group, n=51). There were 11 types of NDKD. Of these, membranous nephropathy was the most common (23.5%), followed by IgA nephropathy (17.6%), and crescentic glomerulonephritis (13.7%). In multiple logistic regression analysis, absence of severe hematuria (odds ratio (OR) 11.66, 95% confidence interval (CI) 1.68 - 89.9) and presence of anemia (OR 11.38, 95% CI 2.51 - 51.52) were significantly related with the diagnosis of DN. Akaike’s information criterion (AIC) and net reclassification improvement (NRI) analyses revealed improved predictive performance by adding anemia to the conventional factors (AIC 100.152 to 91.844; NRI 27.0%). The tissues of patients in the DN group demonstrated more severe interstitial fibrosis and tubular atrophy (IF/TA) than the NDKD group (p&lt;0.05) regardless of the rate of global glomerulosclerosis (figure), and IF/TA was related to the prevalence of anemia (odds ratio: 7.31, 95% confidence interval: 2.33 - 23.00) in multivariate regression analysis. These results suggest DM-associated severe IF/TA (compared with NDKD) impaired erythropoietin production, resulting in earlier anemia, independent of glomerular injuries and renal function. Furthermore, the renal prognosis was significantly better in the NDKD group than in the DN group using Log-rank test (p&lt;0.05).

Conclusion
DN is associated with anemia because of severe IF/TA regardless of renal function, and anemia helps clinician discriminate clinically between isolated DN and NDKD.