Retinopathy in haemoglobin C trait

Sickle trait in African-American hemodialysis patients and higher erythropoiesis-stimulating agent dose

African Americans require higher doses of erythropoiesis-stimulating agents (ESAs) during dialysis to manage anemia, but the influence of sickle cell trait and other hemoglobinopathy traits on anemia in dialysis patients has not been adequately evaluated. We performed a cross-sectional study of a large cohort of adult African-American hemodialysis patients in the United States to determine the prevalence of hemoglobinopathy traits and quantify their influence on ESA dosing. Laboratory and clinical data were obtained over 6 months in 2011. Among 5319 African-American patients, 542 (10.2%) patients had sickle cell trait, and 129 (2.4%) patients had hemoglobin C trait; no other hemoglobinopathy traits were present. Sickle cell trait was more common in this cohort than the general African-American population (10.2% versus 6.5%-8.7%, respectively, P<0.05). Among 5002 patients (10.3% sickle cell trait and 2.4% hemoglobin C trait) receiving ESAs, demographic and clinical variables were similar across groups, with achieved hemoglobin levels being nearly identical. Patients with hemoglobinopathy traits received higher median doses of ESA than patients with normal hemoglobin (4737.4 versus 4364.1 units/treatment, respectively, P=0.02). In multivariable analyses, hemoglobinopathy traits associated with 13.2% more ESA per treatment (P=0.001). Within subgroups, sickle cell trait patients received 13.2% (P=0.003) higher dose and hemoglobin C trait patients exhibited a similar difference (12.9%, P=0.12). Sensitivity analyses using weight-based dosing definitions and separate logistic regression models showed comparable associations. Our findings suggest that the presence of sickle cell trait and hemoglobin C trait may explain, at least in part, prior observations of greater ESA doses administered to African-American dialysis patients relative to Caucasian patients.

Variant hemoglobin phenotypes may account for differential erythropoiesis-stimulating agent dosing in African-American hemodialysis patients

African-American patients with end-stage renal disease have historically lower hemoglobin concentrations and higher requirements of erythropoiesis-stimulating agent (ESA). While disparities in health-care access may partially explain these findings, the role of variant hemoglobin, such as sickle trait, has not been investigated. To clarify this, we evaluated 154 African-American patients receiving in-center hemodialysis with available hemoglobin phenotyping. The primary exposure was any abnormal hemoglobin variant and the primary outcome of higher-dose ESA was defined as a dose of 6500 or more units per treatment. Logistic regression assessed the association between variant hemoglobin and higher-dose ESA. Covariates included age, gender, diabetes, iron parameters, intravenous iron dose, parathyroid hormone, albumin, phosphorus, body mass index, vascular access type, hospitalization/missed treatments, smoking status, alcohol abuse, and gastrointestinal bleeding. Of 33 patients with variant hemoglobin, 24 had HbAS and 9 had HbAC. Univariate odds of higher-dose ESA among those with hemoglobin variants were twice that of those with the normal HbAA phenotype (odds ratio 2.05). In multivariate models, the likelihood of higher-dose ESA had an odds ratio of 3.31 and the nature of this relationship did not change in Poisson regression or sensitivity analyses. Hence, our findings may explain, in part, the difference in ESA dosing between Caucasians and African-Americans with end-stage renal disease but await further study.

Sickle cell trait, hemoglobin C trait, and invasive pneumococcal disease

BACKGROUND

The cause of historically higher rates of invasive pneumococcal disease among blacks than whites has remained unknown. We tested the hypothesis that sickle cell trait or hemoglobin C trait is an independent risk factor for invasive pneumococcal disease.

METHOD

Eligible children were born in Tennessee (1996-2003), had a newborn screen, enrolled in TennCare aged <1 year, and resided in a Tennessee county with laboratory-confirmed, pneumococcal surveillance. Race/ethnicity was ascertained from birth certificates. Children were followed through 2005 until loss of enrollment, pneumococcal disease episode, fifth birthday, or death. We calculated incidence rates by race/ethnicity and hemoglobin type before and after pneumococcal conjugate vaccine (PCV7) introduction. Poisson regression analyses compared invasive pneumococcal disease rates among blacks with sickle cell trait or hemoglobin C trait with whites and blacks with normal hemoglobin, controlling for age, gender, time (pre-PCV7, transition year, or post-PCV7) and high-risk conditions (eg, heart disease).

RESULTS

Over 10 years, 415 invasive pneumococcal disease episodes occurred during 451,594 observed child-years. Before PCV7 introduction, disease rates/100,000 child-years were 2941 for blacks with sickle cell disease, 258 for blacks with sickle cell trait or hemoglobin C trait and 188, 172, and 125 for blacks, whites, and Hispanics with normal hemoglobin. Post-PCV7, rates declined for all groups. Blacks with sickle cell trait or hemoglobin C trait had 77% (95% CI = 22-155) and 42% (95% CI = 1-100) higher rates than whites and blacks with normal hemoglobin.

CONCLUSION

Black children with sickle cell trait or hemoglobin C trait have an increased risk of invasive pneumococcal disease.

Two cases of hematuria with hemoglobin C trait

Patients with sickle cell disease commonly experience painless hematuria. Hematuria may be found in patients with sickle cell trait, sickle cell anemia, and sickle cell hemoglobin C disease, but it is believed to be uncommon in patients with other hemoglobinopathies, such as hemoglobin C disease and hemoglobin C trait. We report two cases of children with hemoglobin C trait who presented with persistent painless hematuria. Because it is possible that hematuria in a patient with hemoglobin C trait is purely coincidental, all patients with a hemoglobinopathy and hematuria should undergo a complete evaluation so as not to overlook other causes of hematuria.

Sickle cell-hemoglobin C retinopathy: transient obstruction of retinal and choroidal circulations and transient drying out of retinal neovessels

We present a case of sickle cell-hemoglobin C disease that presented acute retinal and choroidal peripheral non-perfusion on the base of chronic microvascular obstruction, which transiently closed retinal neovessels.

Retinopathy in sickle cell trait: does it exist?

BACKGROUND

Patients with sickle cell trait and concomitant systemic disease are known to be at risk for proliferative retinopathy. However, there are reports of retinopathy in patients with sickle cell trait without systemic disease. There are no population-based studies addressing the risk of sickle cell retinopathy in this group. We performed a study to clarify the relation between sickle cell trait and retinopathy in healthy subjects.

METHODS

We reviewed the medical records of 100 children with sickle cell disease who attended the Sickle Cell Clinic at the Hospital for Sick Children, Toronto. We then contacted 200 parents with sickle cell trait, of whom 32 agreed to participate in the study. All participants were proven to have hemoglobin AS status with prior hemoglobin electrophoresis. An ophthalmologic history was obtained, and a complete ophthalmologic examination was performed. We defined sickle cell retinopathy as any salmon patch hemorrhages, iridescent spots, black sunbursts, retinal neovascularization or retinal detachment. The evaluation also included attempts to identify the more subtle signs of sickle cell retinopathy, such as optic nerve head vascular changes, vascular tortuosity, macular changes (e.g., microaneurysms and vascular loops) and peripheral arteriovenous anastamoses. Blood samples were obtained for complete blood count, reticulocyte count and smear.

RESULTS

We found no cases of sickle cell retinopathy among the 32 subjects. Ten of 30 subjects had a high reticulocyte count (greater than 120 x 10(9)/L); however, there were no associated eye findings in this subgroup.

INTERPRETATION

Our results indicate that there is no increased risk of retinopathy in healthy people with sickle cell trait.