Dividing CKD Stage 3 Into G3a And G3b Could Better Predict The Prognosis Of IgA Nephropathy

Background Ig A nephropathy(Ig AN)is one of the most common types of primary glomerulonephritis worldwide,and especially in China.The annual incidence is at least 2.5/100 000 adults.Ig AN is the major cause of end-stage renal disease(ESRD)in many countries,and approximately 20–50% of Ig AN patients progress to ESRD within 20 years.In China,Ig AN patients account for 45% of patients with primary glomerulonephritis,with a particular number of young adults being affected,which impacts heavily on families and society.Previous studies have found that in CKD patients a lower estimated glomerular filtration rate(e GFR)is associated with an increased risk for all-cause mortality,cardiovascular events,hospitalization,and infection.The increased risks were evident at an e GFR of less than 60 ml/min/per 1.73 m2 and substantially increased with an e GFR of less than 45 ml/min/per 1.73 m2.As the data suggest different outcomes and risk profiles,CKD stage 3 was divided into categories G3 a and G3 b in the 2013 Kidney Disease Improving Global Outcomes(KDIGO)guidelines.However,CKD patients with different kidney diseases were involved in the above studies.For Ig AN patients with CKD stage 3,whether it is appropriate to regard 45 ml/min/per 1.73 m2 as the threshold value of G3a/G3 b staging,whether dividing CKD stage 3 into G3a/G3 b plays an important role in assessing the risk for all-cause mortality,doubling of serum creatinine,or reaching ESRD in Ig AN patients remains unclear.To investigate these questions,the current study first analyzed the hazard ratios(HR)of reaching defined composite endpoints among Ig AN patients with different e GFR,then compared the clinicopathological data and the prognosis of Ig AN patients in G3 a and G3 b.Finally we assessed whether this new classification was an important risk factor influencing the prognosis of Ig AN patients in CKD stage 3.Objectives This study is set to analyze the clinicopathological data,prognosis,and the risk factors influcing prognosis with CKD stage G3a/G3 b.and investigate whether it is appropriate to regard 45 ml/min/1.73m2 as the threshold value of G3a/G3 b staging and whether diving of CKD stage 3 into G3a/G3 b plays an important role in judging the prognosis in patients with Ig A nephropathy(Ig AN).Methods Three hundred and ninety patients from the First Affiliated Hospital of Zhengzhou University and Peking University First Hospital diagnosed with Ig AN in CKD stage 3 were enrolled and successfully followed up.Cox proportional hazards model was used to analyze hazard ratios of reaching the composite endpoints(doubling of serum creatinine,end-stage renal disease: estimated glomerular filtration rate(e GFR)<15 ml/min/per 1.73 m2 or renal replacement therapy,or all-cause mortality)for patients with different e GFR and risk factors affecting composite endpoints.Analysis of Variance(ANOVA)was used in comparing the differences among the six subgroups with different e GFR.The Kaplan–Meier method was used to calculate the cumulative renal survival rate of patients.Results Three hundred and ninety-nine patients completed the follow-up.To explore HR of reaching endpoints in patients with different e GFR,patients were classified into six subgroups according to e GFR.We found that 45ml/min/per 1.73 m2 was the threshold value to assess the prognosis of Ig AN patients with CKD3.Compared with Ig AN patients in CKD stage G3 a,serum creatinine,urea nitrogen,blood uric acid,serum phosphate,and triglycerides were significantly elevated in Ig AN patients in CKD stage G3b(P<0.05).Hemoglobin and e GFR were significantly decreased in Ig AN patients with CKD stage G3 b compared with Ig AN patients in CKD stage G3a(P<0.05).Proportions of tubulointerstitial injure,mesangial proliferation,and ischemic glomerulosclerosis were greater in patients with CKD stage G3 b compared with CKD stage G3 a.Then we re-divided the patients into G3 a and G3 b stage based on every specified parameter(hypertension/non-hypertension,nephrotic range proteinuria/non-nephrotic range proteinuria,anemia/non-anemia,hyperphosphatemia/ non-hyperphosphatemia respectively).After that,we compared the differences between G3 a and G3 b groups in each parameter.It was found that the cumulative renal survival rates were lower in the G3 b group compared with the G3 a group based on hypertension(P<0.001)and non-hypertension(P<0.001),nephrotic range proteinuria(P<0.001)and non-nephrotic range proteinuria(P<0.001),anemia(P<0.001)and non-anemia(P<0.001),hyperphosphatemia(P<0.001)and non-hyperphosphatemia(P<0.001).tage G3 b at kidney biopsy was a major risk factor affecting the prognosis of Ig AN patients with CKD stage 3.Stage G3 b at kidney biopsy was the most important risk factor affecting the prognosis of Ig AN patients with CKD stage3 second to moderate/severe tubular lesions.Conclusions.A threshold value of 45 ml/min/per 1.73 m2 appears appropriate to assess the prognosis of Ig AN patients with CKD stage 3.Dividing Ig AN patients with CKD stage 3 into G3 a and G3 b is very useful to help understand disease conditions and for predicting the risk for disease progression.