The Impact of Hemoglobin Levels on Patient and Graft Survival in Renal Transplant Recipients

Anemia in Heart Failure: A Perspective from 20-Year Bibliometric Analysis

Background & Objective

Anemia in patients with heart failure (HF) is a growing concern. However, there has no bibliometric analysis in this area up to now. The aim of this study is to explore the status and trends in the field of anemia in HF through the bibliometric analysis, and to provide an outlook on future research.

Methods

We retrieved publications from the Web of Science Core Collection database, and the following data analysis and visualization tools were utilized to perform data processing, statistical computing and graphics generation: VOSviewer (v.1.6.18), CiteSpace (v.6.2 R5), Scimago Graphica (v.1.0.36), Biblimatrix and Microsoft Excel.

Results

We identified a total of 3490 publications from 2004 to 2023. The publications in the field of anemia in HF are growing steadily. The United States, the United Kingdom, and Italy were the leading countries in this area. Stefan D Anker, as the most influential author, held the most total citations and publications. Harvard University was the most productive institution in this area. The European Journal of Heart Failure had published the most papers. Through the analysis of co-citations, 14 major clusters based on cluster labels were identified. Keyword analysis showed that mortality, outcome, prevalence, and risk were the most frequent keywords, and the potential research hotspots in the future will be intravenous iron and iron deficiency.

Conclusion

This study provides a comprehensive analysis of countries, authors, institutions, journals, co-cited references, and keywords in the field of anemia in HF through bibliometric analysis and data visualization. The status, hotspots and future trends in this field offer a reference for in-depth research. Further studies are necessary in the future to broaden the spectrum of research in this field, to evaluate comprehensive approaches to treating anemia in patients with HF, and to find rational targets for the management of anemia.

Variability in hemoglobin levels in hemodialysis patients in the current era: a retrospective cohort study

Background: Given regulatory and reimbursement changes in anemia management, we examined hemoglobin variability in a contemporary cohort of maintenance hemodialysis patients. Materials and methods: The study population included > 200,000 hemodialysis patients with Medicare parts A and B as primary payer on October 1, 2012. Based on 25^th and 75^th percentiles, monthly hemoglobin values were categorized as low, intermediate, or high. Six variability categories were created by patterns during the 6-month observation period. Stable categories were: always-low, always-intermediate, always-high; variable patterns were: varying between low and intermediate, intermediate and high, low and high (most-variable). Cox proportional hazard models were used to assess the association between hemoglobin variability and all-cause mortality or major adverse cardiac events (MACE). Results: The 25^th and 75^th hemoglobin percentiles were 10.2 and 11.5 g/dL, respectively, in 2012, vs. 11 and 12.5 g/dL in 2004. ESA doses were lower in all categories in 2012 and transfusion rates higher, particularly for always-low patients. Hemoglobin variability decreased modestly: in 2004, 6.0% were always-intermediate, vs. 9.5% in 2012. In 2012, more patients were always-high and fewer were most-variable. Mortality hazard ratios (HRs) were higher for patients with any low hemoglobin: always-low (HR, 95% CI: 2.07, 1.84 – 2.31), varying between low and intermediate (1.37, 1.29 – 1.45), and most-variable (1.23, 1.16 – 1.31); the pattern was similar for MACE. Conclusions: In 2012 vs. 2004, hemoglobin levels decreased, the range of levels narrowed, and variability decreased modestly; transfusions increased. The highest risk of mortality and MACE appeared to occur in patients with persistently low, rather than highly variable, hemoglobin levels.


Derivation of a Predictive Model for Graft Loss Following Acute Kidney Injury in Kidney Transplant Recipients

Background:

Acute kidney injury (AKI) is common in the kidney transplant population.

Objective:

To derive a multivariable survival model that predicts time to graft loss following AKI.

Design:

Retrospective cohort study using health care administrative and laboratory databases.

Setting:

Southwestern Ontario (1999-2013) and Ottawa, Ontario, Canada (1996-2013).

Patients:

We included first-time kidney only transplant recipients who had a hospitalization with AKI 6 months or greater following transplant.

Measurements:

AKI was defined using the Acute Kidney Injury Network criteria (stage 1 or greater). The first episode of AKI was included in the analysis. Graft loss was defined by return to dialysis or repeat kidney transplant.

Methods:

We performed a competing risk survival regression analysis using the Fine and Gray method and modified the model into a simple point system. Graft loss with death as a competing event was the primary outcome of interest.

Results:

A total of 315 kidney transplant recipients who had a hospitalization with AKI 6 months or greater following transplant were included. The median (interquartile range) follow-up time was 6.7 (3.3-10.3) years. Graft loss occurred in 27.6% of the cohort. The final model included 6 variables associated with an increased risk of graft loss: younger age, increased severity of AKI, failure to recover from AKI, lower baseline estimated glomerular filtration rate, increased time from kidney transplant to AKI admission, and receipt of a kidney from a deceased donor. The risk score had a concordance probability of 0.75 (95% confidence interval [CI], 0.69-0.82). The predicted 5-year risk of graft loss fell within the 95% CI of the observed risk more than 95% of the time.

Limitations:

The CIs of the estimates were wide, and model overfitting is possible due to the limited sample size; the risk score requires validation to determine its clinical utility.

Conclusions:

Our prognostic risk score uses commonly available information to predict the risk of graft loss in kidney transplant patients hospitalized with AKI. If validated, this predictive model will allow clinicians to identify high-risk patients who may benefit from closer follow-up or targeted enrollment in future intervention trials designed to improve outcomes.

A High Comorbidity Score Should Not be a Contraindication for Kidney Transplantation

BACKGROUND

Currently, potential kidney transplant patients more often suffer from comorbidities. The Charlson Comorbidity Index (CCI) was developed in 1987 and is the most used comorbidity score. We questioned to what extent number and severity of comorbidities interfere with graft and patient survival. Besides, we wondered whether the CCI was best to study the influence of comorbidity in kidney transplant patients.

METHODS

In our center, 1728 transplants were performed between 2000 and 2013. There were 0.8% cases with missing values. Nine pretransplant comorbidity covariates were defined: cardiovascular disease, cerebrovascular accident, peripheral vascular disease, diabetes mellitus, liver disease, lung disease, malignancy, other organ transplantation, and human immunodeficiency virus positivity. The CCI used was unadjusted for recipient age. The Rotterdam Comorbidity in Kidney Transplantation score was developed, and its influence was compared to the CCI. Kaplan-Meier analysis and multivariable Cox proportional hazards analysis, corrected for variables with a known significant influence, were performed.

RESULTS

We noted 325 graft failures and 215 deaths. The only comorbidity covariate that significantly influenced graft failure censored for death was peripheral vascular disease. Patient death was significantly influenced by cardiovascular disease, other organ transplantation, and the total comorbidity scores. Model fit was best with the Rotterdam Comorbidity in Kidney Transplantation score compared to separate comorbidity covariates and the CCI. In the population with the highest comorbidity score, 50% survived more than 10 years.

CONCLUSIONS

Despite the negative influence of comorbidity, patient survival after transplantation is remarkably good. This means that even patients with extensive comorbidity should be considered for transplantation.

Influence of renal function on long-term graft survival and patient survival in renal transplant recipients

OBJECTIVES

Renal function post kidney transplantation is an outcome of interest for both clinicians and regulators evaluating immunosuppressive treatments post-transplantation. The current review sought to provide a synopsis of currently available literature examining the relationship between post-transplantation renal function and long-term graft survival and patient survival.

METHODS

A systematic literature review was performed using the PubMed, EMBASE and Cochrane Library databases. The search strategy was designed based on high level Medical Subject Heading (MeSH) terms and designed to capture studies published in English to 2012 and identified a total of 2683 unique hits; for inclusion studies were required to have >100 patients. Following two rounds of screening, a total of 27 studies were included in the final review (26 of which were identified via the literature review and one study was identified via searches of the reference sections of included studies).

RESULTS

The consensus among studies was that lower post-transplantation GFR, in particular 12 month GFR, was consistently and significantly associated with an increased risk for overall graft loss, death-censored graft loss and all-cause mortality in both univariate and multivariate analyses. The magnitude of the association between reduced GFR and outcomes was greater for death-censored graft loss versus overall graft loss and for graft loss in comparison with overall patient mortality. The predictive utility of GFR alone in predicting long-term outcomes was reported to be limited.

CONCLUSIONS

Lower GFR and greater rates of decline in GFR post-transplantation are associated with an increased risk for graft loss (overall and death-censored) and all-cause mortality; however, the predictive utility of GFR alone in predicting long-term outcomes is limited.

Blood disorders after kidney transplantation

Post transplant anemia (PTA) is a common issue in kidney transplant recipients. Most importantly it is associated with an impaired allograft function. Other important factors associated with PTA are immunosuppressive drugs (MPA, AZA and SRL), iron deficiency, infections (Parvo B19), older donor age, rejection episodes, an increased inflammatory state, and erythropoietin hyporesponsiveness. As there are no adequately powered RCTs in the kidney transplant population on anemia treatment with ESA, we have to rely on what we know from the large RCTs in the CKD population. The recently published KDIGO guidelines do not recommend treatment with ESA if Hb is >10 g/dl. Repletion of iron stores is emphasized. Post transplant leukopenia (PTL) and thrombocytopenia (PTT) are frequent complications especially in the first six months after kidney transplantation. Myelosuppression caused by immunosuppressive agents (MPA, AZA, SRL, rATG), antimicrobial drugs (VGCV), and CMV infection is the predominant cause. There are no widely accepted guidelines on treatment strategies, but most often dose reduction or discontinuation of causative medication is done. Most clinicians tend to decrease MPA dose, but this is eventually associated with an increase in acute rejection episodes. VGCV dose reduction (preemptive treatment instead of CMV prophylaxis) may be a successful strategy. In severe cases G-CSF treatment is an important management option and seems to be safe.

Haemoglobin variability in the early post-transplant period: association with graft survival and mortality

AIM

Haemoglobin (Hb) variability is associated with poor survival in patients with chronic kidney disease. Association of Hb variability after kidney transplantation with patients' and graft survival has not been adequetly studied.

METHODS

This retrospective study used registry data to examine the association between Hb variability in the early post-transplant period (first 6 months) and graft survival after kidney transplantatin. Kaplan-Meier and Cox regression analyses were used for univariate and multivariate associations between mortality, death censored graft survival and the composite outcome of both, in 752 patients after kidney transplantation. Hb values were collected each month during the first 6 months after transplantation, and Hb variavility was calculated using the residual standard deviation method.

RESULTS

The highest quartile of Hb variability was associated with inferior graft and patients' survival in univariate (hazard ratio (HR) 2.18; 95% confidence interval (CI) 1.51 to 3.13; P < 0.001) and multivariate models (HR 1.5; 95% CI 1.029 to 2.18; P = 0.035). This association was mainly due to increased death censored graft failure in the high variability group (HR 2.75; 95% CI 1.73 to 4.38; P < 0.001) and (HR 1.67; 95% CI 1.023 to 2.74; P = 0.04) in the univariate and multivariate models, respectively. There was no association between Hb variability and the risk of death (HR 1.51; 95% CI 0.88 to 2.57; P = 0.132).

CONCLUSION

High Hb variability is independently associated with inferior graft survival in patients after kidney transplantation.

Hemoglobin variability after renal transplantation is associated with mortality

Anemia is a common problem after renal transplantation. Therefore, the patients are treated with erythropoietin stimulating agents (ESAs). The varying response to treatment contributes to hemoglobin variability, which might be associated with mortality. We conducted a retrospective cohort study of first kidney allograft recipients between 1990 and 2008 represented in the Austrian Transplant Registry. We included 1441 patients of whom 683 received ESAs at any time after transplantation. Cox regression with cubic splines and linear estimates and the purposeful selection algorithm of covariables were used. The measure of variability was the moving standard deviation computed at three monthly intervals for the entire graft life. The hazard ratio (HR) of mortality and graft loss in the spline models increased with hemoglobin variability. The linear HR for mortality was 2.35 (95% confidence interval 1.75-3.17, P<0.001) and functional graft loss 2.45 (1.76-3.40, P<0.001). In an adjusted Cox model (ESA use, hemoglobin, age, diabetes, days on dialysis, eGFR, biopsy confirmed acute rejection and year of transplantation), hemoglobin variability was associated with mortality (HR: 2.11; 1.51-2.94; P<0.001). No association with functional graft loss could be detected (HR: 1.34; 0.93-1.93; P=0.121). These findings suggest that hemoglobin variability is associated with mortality of renal allograft recipients.

Anemia and erythrocytosis in patients after kidney transplantation

Anemia is a highly prevalent disorder in recipients of renal allografts. Despite its frequent occurrence, there is still uncertainty with regard to treatment targets and treatment options. This includes questions on appropriate iron management, the choice and dosage of erythropoietin stimulating agents, criteria for the timing of treatment initiation and the targeted hemoglobin values. The review summarizes available data on recent therapeutic strategies for post transplant anemia, as well as for post transplant erythrocytosis, another hematological disorder, that has decreased in recent years.

Serum phosphate and calcium concentrations are associated with reduced patient survival following kidney transplantation

The impact of disordered mineral and bone metabolism following kidney transplantation is not well defined. We studied the association of serum phosphate and calcium concentrations, and surrogate measures of arterial stiffness (augmentation index: AIx and Timing of the reflected wave: Tr), with long-term kidney transplant recipient and allograft survival. Prevalent adult renal transplant patients (n = 270) were prospectively studied over a median 88-month follow-up. Detailed demographic, clinical and laboratory data, in addition to both peripheral and central non-invasive blood pressure measurements, were recorded. Higher serum phosphate and calcium levels were associated with increased all-cause mortality (HR: 1.21; 95% CI 1.09,1.35, p < 0.001 and HR: 1.22; 95% CI 1.01,1.48; p < 0.04, respectively; adjusted Cox model) and death-uncensored graft loss (p < 0.001 and p = 0.03, respectively). In addition, serum calcium and phosphate were associated with death-censored graft loss on univariable analysis (p < 0.001 and p = 0.02, respectively), but did not retain significance on multivariable analysis. AIx and Tr were not associated with mortality or graft loss on multivariable analysis. This is the first report to demonstrate that both higher serum phosphate and calcium levels are associated with increased mortality in kidney transplant recipients. It highlights the need for randomized trials assessing current interventions available for improving disordered mineral-bone metabolism post transplantation.

Anemia and erythrocytosis after kidney transplantation: a 5-year graft function and survival analysis

INTRODUCTION

Both anemia and erythrocytosis frequently occur after kidney transplantation. The aim of this study was to analyze the influence of both anemia and erythrocytosis on kidney graft function and long-term patient outcomes following kidney transplantation.

PATIENTS AND METHODS

Three hundred eight-five consecutive patients with at least 12 months of follow-up after successful kidney transplantation were enrolled into this study. Of the total, 88.3% of patients completed a 5-year follow-up. Anemia occurred in 30.4% of patients (with 17.7% showing a hemoglobin concentration (Hb) <11.0 g/dL), whereas erythrocytosis was observed in 19.0% of patients, including 9.6% with hematocrit (HTC) >55%. We also analyzed graft function every 6 months after transplantation for the impact of anemia or erythrocytosis on the 5-year risk of patient death or graft loss.

RESULTS

In 57.3% of anemia patients the Hb did not reach the normal range during the observation time. The mean eGFR-Modification of Diet in Renal Disease (MDRD) at 12 months after transplantation was significantly lower among patients with anemia: 43.9 mL/min/1.73 m(2) (39.5-48.4) vs 55.3 mL/min/1.73 m(2) (53.0-57.6; P < .001). Better 12-month graft function was observed among patients with erythrocytosis, namely, 57.7 mL/min/1.73 m(2) (53.5-62.0). Anemia but not erythrocytosis was associated with an increased risk of graft loss (hazard ratio [HR] = 4.11 [95% confidence interval (CI) 2.02-8.37]; P < .001).

CONCLUSION

Anemia after transplantation was associated with worse kidney graft function and was a strong predictor of graft loss. Erythrocytosis occurs among patients with excellent allograft function; when properly treated it did not increase the risk of graft loss or death.