Sickle Cell Trait and Renal Function in Hispanics in the United States: The Northern Manhattan Study

Prevalence of sickle cell trait and its association to renal dysfunction among blood donors at University of Medical Sciences Teaching Hospital, Ondo, Nigeria

Introduction

Prospective blood donors are routinely screened for blood borne infections but medical illnesses and haemoglobin genotype are overlooked despite a high prevalence of haemoglobin AS among Nigerian donors.

Objective

To determine the prevalence of haemoglobin AS and its association to renal function, if any.

Method

Apparently healthy donors were studied between February and December 2018. Their haemoglobin genotype and, estimated glomerular filtration rates were determined.

Results

There were 96 males (94.1%) and 6 (5.9%) females with mean age of 26.7±4.5 years (range 19–44 years) and mean eGFR of 103.97±19.00ml/min/1.73m2. Eighty one (79.4%) and 21 (20.6%) subjects had haemoglobin AA and AS genotypes respectively. The mean eGFR for subjects with haemoglobin AA and AS were 105.2±18.6ml/min/1.73m² and 99.9 ± 21.2ml/min/1.73m² respectively (p value = 0.270). Eighty one (79.4%), 20 (19.6%) and 1 (1.0%) subjects had renal function at >90ml/min/1.73m², 60–89ml/min/1.73m² and 30–59ml/min/m² respectively. There was no significant difference in the mean eGFR between subjects with haemoglobin AA and AS (mean difference 5.3, p = 0.265, 95%CI = -4.07 to 14.60).

Conclusion

The prevalence of sickle cell trait among Nigerian blood donors is high. There is no significant difference in the renal function status of blood donors with SCT and normal haemoglobin genotype.

Methods to estimate baseline creatinine and define acute kidney injury in lean Ugandan children with severe malaria: a prospective cohort study

BACKGROUND

Acute kidney injury (AKI) is increasingly recognized as a consequential clinical complication in children with severe malaria. However, approaches to estimate baseline creatinine (bSCr) are not standardized in this unique patient population. Prior to wide-spread utilization, bSCr estimation methods need to be evaluated in many populations, particularly in children from low-income countries.

METHODS

We evaluated six methods to estimate bSCr in Ugandan children aged 6 months to 12 years of age in two cohorts of children with severe malaria (n = 1078) and healthy community children (n = 289). Using isotope dilution mass spectrometry (IDMS)-traceable creatinine measures from community children, we evaluated the bias, accuracy and precision of estimating bSCr using height-dependent and height-independent estimated glomerular filtration (eGFR) equations to back-calculate bSCr or estimating bSCr directly using published or population-specific norms.

RESULTS

We compared methods to estimate bSCr in healthy community children against the IDMS-traceable SCr measure. The Pottel-age based equation, assuming a normal GFR of 120 mL/min per 1.73m², was the more accurate method with minimal bias when compared to the Schwartz height-based equation. Using the different bSCr estimates, we demonstrated the prevalence of KDIGO-defined AKI in children with severe malaria ranged from 15.6-43.4%. The lowest estimate was derived using population upper levels of normal and the highest estimate was derived using the mean GFR of the community children (137 mL/min per 1.73m²) to back-calculate the bSCr. Irrespective of approach, AKI was strongly associated with mortality with a step-wise increase in mortality across AKI stages (p < 0.0001 for all). AKI defined using the Pottel-age based equation to estimate bSCr showed the strongest relationship with mortality with a risk ratio of 5.13 (95% CI 3.03-8.68) adjusting for child age and sex.

CONCLUSIONS

We recommend using height-independent age-based approaches to estimate bSCr in hospitalized children in sub-Saharan Africa due to challenges in accurate height measurements and undernutrition which may impact bSCr estimates. In this population the Pottel-age based GFR estimating equation obtained comparable bSCr estimates to population-based estimates in healthy children.

Kidney Function Decline among Black Patients with Sickle Cell Trait and Sickle Cell Disease: An Observational Cohort Study

BACKGROUND

Sickle cell trait and sickle cell disease are thought to be independent risk factors for CKD, but the trajectory and predictors of kidney function decline in patients with these phenotypes are not well understood.

METHODS

Our multicenter, observational study used registry data (collected January 2005 through June 2018) and included adult black patients with sickle cell trait or disease (exposures) or normal hemoglobin phenotype (reference) status (ascertained by electrophoresis) and at least 1 year of follow-up and three eGFR values. We used linear mixed models to evaluate the difference in the mean change in eGFR per year.

RESULTS

We identified 1251 patients with sickle cell trait, 230 with sickle cell disease, and 8729 reference patients, with a median follow-up of 8 years. After adjustment, eGFR declined significantly faster in patients with sickle cell trait or sickle cell disease compared with reference patients; it also declined significantly faster in patients with sickle cell disease than in patients with sickle cell trait. Male sex, diabetes mellitus, and baseline eGFR ≥90 ml/min per 1.73 m² were associated with faster eGFR decline for both phenotypes. In sickle cell trait, low hemoglobin S and elevated hemoglobin A were associated with faster eGFR decline, but elevated hemoglobins F and A₂ were renoprotective.

CONCLUSIONS

Sickle cell trait and disease are associated with faster eGFR decline in black patients, with faster decline in sickle cell disease. Low hemoglobin S was associated with faster eGFR decline in sickle cell trait but may be confounded by concurrent hemoglobinopathies. Prospective and mechanistic studies are needed to develop best practices to attenuate eGFR decline in such patients.

Association Between Sickle Cell Trait With Selected Chronic Medical Conditions in U.S. Service Members

Introduction

Sickle cell trait (SCT), the heterozygous carrier state for hemoglobin S, is present in an estimated 1.6% of all newborns and 7.3% in black individuals in the USA. SCT has long been considered a benign condition with anticipated normal life expectancy and no increased risk for chronic diseases. The medical literature is inconclusive on the potential association between SCT and chronic medical conditions (CMC) including chronic kidney disease, venous thromboembolism, and stroke. Studies addressing these questions are lacking particularly in non-Black young adults.

Materials and Methods

We conducted a retrospective cohort study among U.S. active duty, enlisted, service members who entered from 1992 to 2012 using existing Department of Defense (DoD Military Healthcare System databases). SCT positive subjects (1,323) were matched by demographic characteristics to SCT negative subjects (3,136) and followed through 2013 for CMC that included deep vein thrombosis, diabetes mellitus and hematologic, pulmonary, and renal conditions.

Results

The rate of developing any of the included CMC was higher for those with SCT (incidence rate ratio = 1.71 95% CI 1.61-1.81) compared with those who were SCT negative and their healthcare utilization rate for any of CMC studied was higher for SCT positive compared with negative individuals (URR = 2.45 95% CI 2.41-2.50), with the highest rate ratios observed for hematologic and renal conditions. SCT positive compared with negative individuals were more likely to have encounter diagnoses of sickle cell disease and diabetes Type II and were less likely to have encounter diagnoses of other hemoglobinopathies and diabetes type I.

Conclusion

SCT in these racially diverse, young adults increased both the incidence of and healthcare utilization for thromboembolism, diabetes mellitus type II, sickle cell disease, pulmonary, and chronic renal conditions. These findings suggest that clinicians treating young adults with SCT should exercise heightened surveillance for these CMC to ensure both early diagnosis and access to treatments.

Sickle cell trait and renal disease among African American U.S. Army soldiers

Sickle cell trait and certain renal disorders are disproportionately prevalent among African American individuals, so a clear understanding of their association is important. We conducted a longitudinal study using the Stanford Military Data Repository to examine sickle cell trait in relation to the incidence of acute kidney injury (AKI) and chronic kidney disease (CKD). Our study population consisted of African American U.S. Army soldiers on active duty between January 2011 and December 2014. The cumulative incidence was 0·51% for AKI (236 cases out of 45 901 soldiers) and 0·56% for CKD (255 cases out of 45 882 soldiers). Discrete time logistic regression models adjusting for demographic-, military- and healthcare-related covariates showed that sickle cell trait was associated with significantly higher adjusted odds of both AKI [odds ratio (OR): 1·74; 95% confidence interval (CI): 1·17-2·59] and CKD (OR: 2·00; 95% CI: 1·39-2·88). Elevated odds of AKI and CKD were also observed in association with prior CKD and AKI, respectively, and with obesity and prior hypertension. Individuals with sickle cell trait and their providers should be aware of the possibility of increased risk of AKI and CKD to allow for timely intervention and possible prevention.

Clinical Outcomes Associated With Sickle Cell Trait: A Systematic Review

Background

Although sickle cell trait (SCT) is largely a benign carrier state, it may increase risk for certain clinical outcomes.

Purpose

To evaluate associations between SCT and clinical outcomes in children and adults.

Data Sources

English-language searches of PubMed, CINAHL, the Cochrane Library, Current Contents Connect, Scopus, and Embase (1 January 1970 to 30 June 2018) and bibliographies of review articles.

Study Selection

Observational controlled studies (published in English) in children or adults that examined an association between SCT and any of 24 clinical outcomes specified a priori in the following 6 categories: exertion-related injury; renal, vascular, pediatric, and surgery- or trauma-related outcomes; and overall mortality.

Data Extraction

A single reviewer extracted study data, which was checked by another; 2 reviewers independently assessed study quality; and strength of evidence was assessed by consensus.

Data Synthesis

Of 7083 screened studies, 41 met inclusion criteria. High-strength evidence supported a positive association between SCT and risk for pulmonary embolism, proteinuria, and chronic kidney disease. Moderate-strength evidence supported a positive association between SCT and exertional rhabdomyolysis and a null association between SCT and deep venous thrombosis, heart failure or cardiomyopathy, stroke, and pediatric height or weight. Absolute risks for thromboembolism and rhabdomyolysis were small. For the remaining 15 clinical outcomes, data were insufficient or strength of evidence was low.

Limitation

Publication bias was possible, and high-quality evidence was scant.

Conclusion

Sickle cell trait is a risk factor for a few adverse health outcomes, such as pulmonary embolism, kidney disease, and exertional rhabdomyolysis, but does not seem to be associated with such complications as heart failure and stroke. Insufficient data or low-strength evidence exists for most speculated complications of SCT.

Primary Funding Source

National Human Genome Research Institute.