Significance Of Serum Uric Acid Level In IgA Nephropathy

Objective: IgA nephropathy(IgAN)is the most common primary glomerular disease,with different prognosises as well as various pathological and clinical manifestations.The purpose of this study was to analyze the related clinical and pathological factors for hyperuricemia(HUA)in patients with IgAN and to explore the significance of serum uric acid level in the disease assessment and prognosis evaluation of IgAN patients.Methods: A total of 275,biopsy-proven IgAN patients,in the Nephrology Department of Dalian Central Hospital and the Nephrology Department of the Second Affiliated Hospital of Dalian Medical University from 2008 January to 2016 January were enrolled.Exclusion criteria: systemic lupus erythematosus,Henoch-Schonlein purpura,ankylosing spondylitis,autoimmune disease and other secondary IgAN;history of gout;patients on continuous medication which affected serum uric acid and uric acid excretion in the previous 30 days of hospitalization;serious infection,chronic consumption disease such as malignant neoplsm and tuberculosis;serious or active hepatobiliary diseases;serious or acute cardiovascular diseases;patients after kidney transplantation;total biopsy glomerular number less than 8 under light microscope.Basic clinical information of all the research subjects,including gender,age,body mass index and so on were collected.Hemoglobin,albumin,triglyceride,cholesterol,low density lipoprotein-cholesterol,high density lipoprotein-cholesterol,serum creatinie,serum uric acid,urinary uric acid(24-hour)and urinary protein(24-hour)were assessed by autobiochemistry machine.Urine samples were evaluated by microscopyand urine analyzer techniques.Percutaneous renal biopsy was performed in each patient and slides were made from pathological sample specimens.Pathological observation by Light microscope and Immunofluorescence were then made by two senior pathologists in our department.The pathologists were unaware of the clinical information of the subjects and they carried out independent and unbiased examinations as far as possible.Electron microscope diagnosises were made by the Electron Microscope Room of the First Hospital of Peking University All statistical analyses were performed using SPSS 22.0.P values<0.05 were comsidered as statistically significant.Results:1.This study included 275 confirmed cases of IgAN,104 of whom were diagnosed with HUA,with a incidence rate of 37.82%;There were 137 IgAN patients with normal renal function(Chronic Kidney Disease in Stage One),34 of whom had HUA,with a incidence rate of 24.82%.2.The proportion of males to females,BMI,SBP and incidence of hypertension,TG,TC,serum creatine,serum Cys C and 24 hours-urinary protein content in IgAN group were higher than those of normal uric acid(NUA)group,while the eGFR of HUA group was lower that of the NUA group(P<0.05).3.The Lee's pathological grades were higher in HUA group than in NUA group(P<0.05).The degrees and the incidences of mesangial cells proliferation,tubulointerstitial lesions,segmental sclerosis and global glomerulosclerosis according to the Oxford Classification Score System were higher in HUA group than in NUA group(P<0.05).The score of renal vascular lesions assessed by the Semiquantive method according to Katafuchi were higher in HUA group than in NUA group(P<0.05).4.Logistics regression analysis showed that the independent risk factors of HUA in IgAN patients were tubulointerstitial lesions(OR=2.125),elevated serum triglycerides(OR=1.246),increased BMI(OR=1.105)and renal function impairment(OR=1.013),P<0.01.For patients with normal renal function,the independent riskfactors were tubulointerstitial lesions(OR=2.311),elevated serum triglycerides(OR=1.537),and increased BMI(OR=1.091),P<0.01.5.For the 24 patients with normal renal function,there are 15 patients with decreased fraction excretion of uric acid(63%),1 patient with increased fraction excretion of uric acid(63%),8 patients with a intermediate fraction excretion of uric acid(33%);The incidences of different tubulointerstitial lesions between groups with and without decreased fraction excretion of uric acid were different(P<0.05).Logistics regression analysis showed that the independent risk factors of decreased fraction excretion of uric acid in IgAN patients was tubulointerstitial lesions(OR=0.348),P<0.05;6.The average level of serum uric acid is significantly higher in group with T1~2than in group with T0.The serum uric acid level was positively correlated with the severity of tubulointerstitial lesions(r=0.589,P<0.001).Logistics regression analysis showed that HUA was the independent risk factor of tubulointerstitial lesions in IgAN cases(OR=1.124,P<0.05).It had improved sensitivity(78.57%)in the normal renanl function group than in the whole objects(sensitivity 74.74%)for HUA prediction of tubulointerstitial lesions.Conclusions:The incidence rate of hyperuricemia is high in IgA Nephropathy cases,the independent risk factors of HUA in IgAN patients are tubulointerstitial lesions,kidney function impairment,obesity and hypertriglyceridemia.While,for patients with normal renal function,the independent risk factors are tubulointerstitial lesions,obesity and hypertriglyceridemia.On the other hand,hyperuricemia is also the independent risk factor of tubulointerstitial lesions.Therefore,serum uric acid level may have some significance in the disease assessment and prognosis evaluation of IgAN patients.