Is serum hemoglobin level an independent prognostic factor for IgA nephropathy?: a systematic review and meta-analysis of observational cohort studies.

BACKGROUND: Decreased serum hemoglobin (Hb) level is associated with Immunoglobulin A nephropathy (IgAN) progression. However, whether serum Hb level is an independent prognostic factor of IgAN remains controversial. Herein, we aimed to investigate the prognostic value of serum Hb level in IgAN. METHODS: The Cochrane Library, Embase, PubMed and Open Grey databases were systematically searched and reviewed. Kidney disease progression of IgAN was defined as a doubling of serum creatinine (SCr), a 30% reduction in estimated glomerular filtration rate (eGFR), end-stage renal disease (ESRD), or death. We evaluated the hazard ratio (HR) between serum Hb level and the incidence of kidney disease progression in IgAN before and after adjusting for relevant covariates. RESULTS: We included nine studies with 10006 patients in the meta-analysis. As a continuous variable, we found that serum Hb was an independent prognostic factor of IgAN [unadjusted HR = 0.89, 95% confidence interval (CI) = 0.84-0.95, I2 = 98%; adjusted HR = 0.85, 95% CI = 0.79-0.91, I2 = 0%]. The sensitivity analysis confirmed the stability of these results. Consistently, as a dichotomous variable defined as the below/above cutoff for anemia, we observed a positive correlation between serum Hb and kidney disease progression in IgAN (unadjusted HR = 2.12, 95% CI = 1.44-3.12, I2 = 79%; adjusted HR = 1.65, 95% CI = 1.20-2.27, I2 = 0%). CONCLUSION: Serum Hb level was independently correlated with the incidence of kidney disease progression in IgAN.

Is hyperuricemia an independent prognostic factor for IgA nephropathy: a systematic review and meta-analysis of observational cohort studies.

BACKGROUND: Hyperuricemia has been reported to be correlated with IgA nephropathy (IgAN). However, whether hyperuricemia or elevated serum uric acid (SUA) is an independent prognostic factor of IgAN remains unknown. Therefore, this systematic review and meta-analysis evaluated the prognostic value of hyperuricemia and elevated SUA in IgAN. METHODS: Databases including PubMed, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), and Open Gray were reviewed systematically. The kidney failure events of IgAN were defined as a doubling of serum creatinine, halving of eGFR, end-stage renal disease (ESRD), or death. The risk ratio (RR) between hyperuricemia and IgAN-caused kidney failure was evaluated before and after adjustment for relevant covariates. The RR between elevated SUA and IgAN-caused kidney failure was evaluated after adjustment for relevant covariates. RESULTS: A total of 11 548 patients from 14 studies were included in this meta-analysis. Hyperuricemia was found to be an independent prognostic factor of IgAN (unadjusted RR = 2.79, 95% CI = 1.93-4.03, p for heterogeneity <0.00001, I2 = 91%; adjusted RR = 2.12, 95% CI = 1.64-2.73, p for heterogeneity = 0.86, I2 = 0%). Subgroup and sensitivity analyses confirmed the stability of these results. Similarly, elevated SUA was positively correlated with kidney failure events of IgAN (adjusted RR = 1.25, 95% CI = 1.19-1.31, p for heterogeneity = 0.6, I2 = 0%). CONCLUSION: Our meta-analysis showed that hyperuricemia and elevated SUA were both independently associated with an increased incidence of kidney failure events in IgAN patients.