Anemia and low-grade inflammation in pediatric kidney transplant recipients

Anemia after kidney transplantation

Anemia is a frequent complication in pediatric kidney transplant recipients (KTR) with a variable reported prevalence estimated between 20 and 80% depending on how defined. Causes of and risk factors for post-transplantation anemia (PTA) are multifactorial with iron deficiency being the primary cause of early PTA (within the first 6 months after transplantation) and impaired glomerular filtration rate (GFR) commonly responsible for late PTA (after 6 months). Medications, viral infections, chronic inflammation, and comorbidities also play a role. PTA has relevant long-term consequences and is a potential risk factor for allograft dysfunction, cardiovascular morbidity, and mortality. Thus, an anemia evaluation, approximately 3 months post-transplantation, is recommended in order to start early treatment and improve prognosis. Iron status, vitamin B12, folate, markers of hemolysis, and viral PCR should be checked, and medications, in particular combinations of medications, should be carefully evaluated. PTA treatment may be challenging and should be directed to the underlying causes. Iron supplementation and erythropoietin therapy, not extensively used in KTR, may be indicated. Every effort should be made to avoid blood transfusions in the pre-transplant period to avoid allosensitization. Anemia should be corrected to prepare candidates for kidney transplantation in order to reduce the need for perioperative blood transfusions as well.

Anemia in Pediatric Kidney Transplant Recipients-Etiologies and Management

Posttransplant anemia (PTA) is a common complication of pediatric kidney transplantation, with a prevalence ranging from 22 to 85%. PTA is categorized as early (within 6 months posttransplant) and late (>6 months posttransplant). Early PTA is typically associated with surgical blood losses and iron deficiency. Late PTA primarily results from graft dysfunction; however, iron deficiency, drug toxicity, and posttransplant inflammation also play a role. PTA is more severe compared with the anemia in glomerular-filtration-rate matched patients with native chronic kidney disease. Treatment of PTA is directed toward the underlying cause. Erythropoiesis stimulating agents (ESA) are effective; however, their use is limited in the transplant setting. Timely diagnosis and treatment of PTA are vital to prevent long-term adverse outcomes in pediatric transplant recipients.

Associations among erythropoietic, iron-related, and FGF23 parameters in pediatric kidney transplant recipients

BACKGROUND

In pediatric kidney transplant recipients, anemia is common and oftentimes multifactorial. Hemoglobin concentrations may be affected by traditional factors, such as kidney function and iron status, as well as novel parameters, such as fibroblast growth factor 23 (FGF23).

METHODS

Here, we evaluated associations among erythropoietic, iron-related, and FGF23 parameters in a cohort of pediatric kidney transplant recipients, hypothesizing that multiple factors are associated with hemoglobin concentrations.

RESULTS

In a cross-sectional analysis of 59 pediatric kidney transplant recipients (median (interquartile range) age 16.3 (13.5, 18.6) years, median estimated glomerular filtration rate (eGFR) 67 (54, 87) ml/min/1.73 m²), the median age-related hemoglobin standard deviation score (SDS) was -2.1 (-3.3, -1.1). Hemoglobin SDS was positively associated with eGFR and calcium, and was inversely associated with erythropoietin (EPO), mycophenolate dose, and total, but not intact, FGF23. In multivariable analysis, total FGF23 remained inversely associated with hemoglobin SDS, independent of eGFR, iron parameters, EPO, and inflammatory markers, suggesting a novel FGF23-hemoglobin association in pediatric kidney transplant patients. In a subset of patients with repeat measurements, only delta hepcidin was inversely associated with delta hemoglobin SDS. Also, delta EPO positively correlated with delta erythroferrone (ERFE), and delta ERFE inversely correlated with delta hepcidin, suggesting a possible physiologic role for the EPO-ERFE-hepcidin axis in the setting of chronic kidney disease (CKD).

CONCLUSION

Our study provides further insight into factors potentially associated with erythropoiesis in pediatric kidney transplant recipients. A higher resolution version of the Graphical abstract is available as Supplementary information.

Anemia after kidney transplantation: Does its basis differ from anemia in chronic kidney disease?

BACKGROUND

Although similar factors play a role in both PTA and anemia in patients with CKD, additional risk factors exist in the pathogenesis of PTA. The present study aimed at comparing anemia and inflammation-related parameters between RTx recipients and CKD patients and elucidating the risk factors of PTA.

METHODS

This single-centered, cross-sectional study consisted of 68 participants: 48 were in the RTx group and 20 were in the CKD group. The CKD patients were comparable to the RTx recipients in terms of age, gender, and eGFR. Serum levels of EPO, hepcidin, and IL-6 were measured by enzyme-linked immunosorbent assays. The ratio of EPO/Hb was calculated to estimate endogenous EPO resistance.

RESULTS

The prevalence of anemia was 46% in the RTx group and 30% in the CKD group (P = .23). RTx recipients had significantly lower Hb (P = .04), higher EPO (P < .001), and ferritin levels (P = .001), and higher EPO/Hb ratios (P < .001); however, CKD patients showed a higher frequency of absolute iron deficiency (P = .008). Neither hepcidin nor IL-6 levels differed between the two groups. Hb level of RTx recipients was correlated with only eGFR (r = .437, P = .002) but not with any of the transplantation-related factors, while Fe level was the only parameter to be correlated with Hb level of CKD patients (r = .622, P = .01).

CONCLUSION

In the present study comparing GFR-matched RTx and CKD patients, lower GFR level appears to be the factor most strongly associated with anemia, and endogenous EPO resistance is among the contributing factors to PTA.