MALDI-MS in first-line screening of newborns for sickle cell disease: results from a prospective study in comparison to HPLC

OBJECTIVES

Newborn screening (NBS) for sickle cell disease (SCD) requires a robust, high-throughput method to detect hemoglobin S (HbS). Screening for SCD is performed by qualitative methods, such as isoelectric focusing (IEF), and both qualitative and quantitative methods such as high performance liquid chromatography (HPLC), capillary electrophoresis (CE), and tandem mass spectrometry (MS/MS). All these methods detect HbS, as well as low-level or absent HbA, and also other variants of hemoglobin. HPLC is considered as a reference method for NBS, because of its high sensitivity and specificity in detecting HbS. NeoSickle®, a fully automated matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) platform, combined with automated sample processing, a laboratory information management system and NeoSickle® software for automatic data interpretation, has increased the throughput of SCD testing. The purpose of this study was to compare the performances of NeoSickle® and HPLC.

METHODS

A prospective study was conducted including 9,571 samples from the NBS program to compare MALDI-MS using NeoSickle® with an HPLC method. Correlation between the two methods was studied. For the MALDI-MS method, sensitivity, specificity, NPV, and PPV were calculated.

RESULTS

We found over 99.4 % correlation between the HPLC and MALDI-MS results. NeoSickle® showed 100 % of sensitivity and specificity in detecting SCD syndrome, leading to positive and negative predictive values of 100 %.

CONCLUSIONS

NeoSickle® is adapted to NBS for SCD, and can be used in first-line high-throughput screening to detect HbS, and beta-thalassemia major warning. When HbS is detected, second-line use of another specific method as HPLC is necessary.

Using the daily rate of rise in hemoglobin S to manage RBC depletion/exchange treatment in sickle cell disease

BACKGROUND

Red blood cell exchange is often used prophylactically in patients with sickle cell disease, with the goal to maintain hemoglobin S (HbS) below a target threshold level. We reviewed whether the daily "rate of rise" (RoR) in HbS that occurs between procedures can be used for patient management. For some patients not achieving their HbS goals despite efficient exchanges, the post-procedure hematocrit (Hct) target is increased to potentially suppress HbS production. This case series explores the utility of this approach, other clinical uses of the daily RoR in HbS, and the factors that influence it.

STUDY DESIGN AND METHODS

A total of 660 procedures from 24 patients undergoing prophylactic RBC depletion/exchange procedures were included. Laboratory values and clinical parameters were collected and used to calculate the daily RoR in HbS. Factors such as Hct or medications that might influence the RoR in HbS were evaluated.

RESULTS

The RoR in HbS varied widely between patients but remained relatively stable within individuals. Surprisingly, this value was not significantly influenced by changes in post-procedure Hct or concurrent hydroxyurea use. A patient's average RoR in HbS effectively predicted the pre-procedure HbS at the following visit (R2 = 0.65).

DISCUSSION

The RoR in HbS is a relatively consistent parameter for individual patients that is unaffected by medication use or procedural Hct targets and may be useful in determining intervals between procedures.

Potential for a large-scale newborn screening strategy for sickle cell disease in Mali: A comparative diagnostic performance study of two rapid diagnostic tests (SickleScan® and HemotypeSC®) on cord blood

Sickle cell disease (SCD) is a life-threatening disease requiring reliable early diagnosis. We assessed the acceptability and diagnostic performances of two rapid diagnostic tests (RDTs) to identify SCD (HbSS, HbSC, HbS/β-thalassaemia) or SCD carrier (HbS/HbC) in a pilot SCD newborn screening (NBS) strategy in Mali. All consenting delivering women were offered SCD NBS using cord blood sampling on two RDTs (SickleScan® and HemotypeSC®) compared to the high-performance liquid chromatography (HPLC) gold standard to detect SCD states. From April 2021 to August 2021, 4333 delivering women were eligible of whom 96.1% were offered NBS: 1.6% refused, 13.8% delivered before consenting and 84.6% consented; 3648 newborns were diagnosed by HPLC; 1.64% had SCD (0.63% HbSS, 0.85% HbSC, 0.16 HbS/β-plus-thalassaemia); 21.79% were SCD carrier. To detect accurately SCD, SickleScan® had a sensitivity of 81.67% (95% confidence interval [CI]: 71.88-91.46) and a negative predictive value (NPV) of 99.69% (95% CI: 99.51-99.87); HemotypeSC® had a sensitivity of 78.33% (95% CI: 67.91-88.76) and a NPV of 99.64% (95% CI: 99.44-99.83). To detect SCD carrier: SickleScan® sensitivity was 96.10% (95% CI: 94.75-97.45) and NPV, 98.90% (95% CI: 98.51-99.29); HemotypeSC® sensitivity was 95.22% (95% CI: 93.74-96.70) and NPV, 98.66% (95% CI: 98.24-99.03). Routine SCD NBS was acceptable. Compared with HPLC, both RDTs had reliable diagnostic performances to exclude SCD-free newborns and to identify SCD carriers to be further confirmed. This strategy could be implemented in large-scale NBS programmes.

High Throughput Newborn Screening for Sickle Cell Disease - Application of Two-Tiered Testing with a qPCR-Based Primary screen

BACKGROUND

Sickle cell disease (SCD) is a group of hemoglobinopathies with a common point mutation causing the production of sickle cell hemoglobin (HbS). In high-throughput newborn screening (NBS) for SCD, a two-step procedure is suitable, in which qPCR first pre-selects relevant samples that are differentiated by a second method.

METHODS

Three NBS centers using qPCR-based primary screening for SCD performed a laboratory comparison. Methods using tandem MS or HPLC were used for differentiation.

RESULTS

In a benchmarking test, 450 dried blood samples were analyzed. Samples containing HbS were detected as reliably by qPCR as by methods established for hemoglobinopathy testing. In a two-step screening approach, the 2nd-tier-analyses have to distinguish the carrier status from pathological variants. In nine months of regular screening, a total of 353,219 samples were analyzed using two-stage NBS procedures. The 1st-tier screening by qPCR reduced the number of samples for subsequent differentiation by>99.5%. Cases with carrier status or other variants were identified as inconspicuous while 78 cases with SCD were revealed. The derived incidence of 1:4,773, is in good agreement with previously published incidences.

CONCLUSION

In high-throughput NBS for SCD, qPCR is suitable to focus 2nd-tier analyses on samples containing HbS, while being unaffected by factors such as prematurity or transfusions. The substantial reduction of samples numbers positively impacts resource conservation, sustainability, and cost-effectiveness. No false negative cases came to attention.

Factors affecting the evaluation and use of a hemoglobin A2 method – lot-to-lot variation, long-term deviation and carry-over

BACKGROUND

We compared two Hb A₂ methods, high pressure liquid chromatography and capillary zone electrophoresis, at two occasions. In 2014 the methods showed good agreement, while in 2020 HPLC results were clearly higher than CE results. This finding prompted us to investigate the external quality assessment (EQA) outcome and our total patient results obtained by high pressure liquid chromatography over several years.

METHODS

The methods compared were Bio-Rad Variant II Beta-Thal Short Program (HPLC) and Sebia Capilllarys Flex Piercing (CE).

RESULTS

Our annual patient results obtained by HPLC increased significantly from 2014 to 2020. A similar trend was also seen in our EQA results. When patient results were grouped according to different reagent lots it became evident that method comparisons might be severely affected by lot-to-lot variation. We also noticed that samples analyzed with the HPLC method following a sample containing a high proportion of Hb E where prone to give falsely increased Hb A₂ results.

CONCLUSION

Standardization of the measurement of Hb A₂ is urgently needed. Furthermore, the lot-to-lot variation must be minimized. While waiting for these improvements each laboratory ought to repeatedly evaluate their distribution of patient Hb A₂ results.

Hydroxyurea in children with sickle cell disease in a resource-poor setting: Monitoring and effects of therapy. A practical perspective

BACKGROUND

Although effectiveness of hydroxyurea (HU) in sickle cell disease is well established, unanswered questions persist about its use in African children. We determined real-life issues of acceptability, availability, and monitoring of HU use in Nigeria.

METHODS

A retrospective longitudinal review of laboratory data of patients on HU was done from case files, followed by a cross-sectional survey that captured families' perception of medication and clinic adherence, laboratory tests, benefits, side effects, and acceptability.

RESULTS

One hundred sixteen patients (1.2-17 years) received HU (mean ± SD = 18.5 ± 4.3 mg/kg/day) in 33 months. Eighty-nine had laboratory analysis. Dose escalation was the initial goal, but only 80% of patients had some form of it. Parents reported improvement in general well-being and reduction in bone pain episodes, hospital admissions, and blood transfusion. While most parents (89.5%) reported satisfaction with HU, 61% reported dissatisfaction with daily drug use, and the frequency and cost of monitoring. Sixteen percent voluntarily stopped therapy. Adherence to daily HU was 88.8%, doctor's appointments 24.5%, hematology tests 18.9%, and organ function tests 37.4%. There were no significant toxicities. Significant increases in hemoglobin, hemoglobin F and mean corpuscular volume, and reduction in absolute neutrophil count occurred despite inconsistent dose escalation.

CONCLUSION

HU (10-15 mg/kg/day starting dose) is safe and seems effective and acceptable to parents. Parental commitment to therapy, pre-HU education (that continues during therapy), provision of affordable HU, and subsidized laboratory tests are important considerations for initiating therapy. Special HU clinics may facilitate dose escalation and reduce frequency of monitoring. Studies are needed on feasibility of maximum tolerable dose HU protocols in sub-Saharan Africa without compromising safety.

Inhibition of Band 3 tyrosine phosphorylation: a new mechanism for treatment of sickle cell disease

Many hypotheses have been proposed to explain how a glutamate to valine substitution in sickle haemoglobin (HbS) can cause sickle cell disease (SCD). We propose and document a new mechanism in which elevated tyrosine phosphorylation of Band 3 initiates sequelae that cause vaso-occlusion and the symptoms of SCD. In this mechanism, denaturation of HbS and release of heme generate intracellular oxidants which cause inhibition of erythrocyte tyrosine phosphatases, thus permitting constitutive tyrosine phosphorylation of Band 3. This phosphorylation in turn induces dissociation of the spectrin-actin cytoskeleton from the membrane, leading to membrane weakening, discharge of membrane-derived microparticles (which initiate the coagulation cascade) and release of cell-free HbS (which consumes nitric oxide) and activates the endothelium to express adhesion receptors). These processes promote vaso-occlusive events which cause SCD. We further show that inhibitors of Syk tyrosine kinase block Band 3 tyrosine phosphorylation, prevent release of cell-free Hb, inhibit discharge of membrane-derived microparticles, increase sickle cell deformability, reduce sickle cell adhesion to human endothelial cells, and enhance sickle cell flow through microcapillaries. In view of reports that imatinib (a Syk inhibitor) successfully treats symptoms of sickle cell disease, we suggest that Syk tyrosine kinase inhibitors warrant repurposing as potential treatments for SCD.

Mendelian Randomization Analysis of Hemoglobin A1c as a Risk Factor for Coronary Artery Disease

OBJECTIVE

Observational studies show that higher hemoglobin A1c (A1C) predicts coronary artery disease (CAD). It remains unclear whether this association is driven entirely by glycemia. We used Mendelian randomization (MR) to test whether A1C is causally associated with CAD through glycemic and/or nonglycemic factors.

RESEARCH DESIGN AND METHODS

To examine the association of A1C with CAD, we selected 50 A1C-associated variants (log10 Bayes factor ≥6) from an A1C genome-wide association study (GWAS; n = 159,940) and performed an inverse-variance weighted average of variant-specific causal estimates from CAD GWAS data (CARDIoGRAMplusC4D; 60,801 CAD case subjects/123,504 control subjects). We then replicated results in UK Biobank (18,915 CAD case subjects/455,971 control subjects) and meta-analyzed all results. Next, we conducted analyses using two subsets of variants, 16 variants associated with glycemic measures (fasting or 2-h glucose) and 20 variants associated with erythrocyte indices (e.g., hemoglobin [Hb]) but not glycemic measures. In additional MR analyses, we tested the association of Hb with A1C and CAD.

RESULTS

Genetically increased A1C was associated with higher CAD risk (odds ratio [OR] 1.61 [95% CI 1.40, 1.84] per %-unit, P = 6.9 × 10-12). Higher A1C was associated with increased CAD risk when using only glycemic variants (OR 2.23 [1.73, 2.89], P = 1.0 × 10-9) and when using only erythrocytic variants (OR 1.30 [1.08, 1.57], P = 0.006). Genetically decreased Hb, with concomitantly decreased mean corpuscular volume, was associated with higher A1C (0.30 [0.27, 0.33] %-unit, P = 2.9 × 10-6) per g/dL and higher CAD risk (OR 1.19 [1.04, 1.37], P = 0.02).

CONCLUSIONS

Genetic evidence supports a causal link between higher A1C and higher CAD risk. This relationship is driven not only by glycemic but also by erythrocytic, glycemia-independent factors.

Clinical and genetic ancestry profile of a large multi-centre sickle cell disease cohort in Brazil

Approximately 3500 children with sickle cell disease (SCD) are born in Brazil each year, but the burden of SCD morbidity is not fully characterised. A large, multi-centre cohort was established to characterise clinical outcomes in the Brazilian SCD population and create the infrastructure to perform genotype-phenotype association studies. Eligible patients were randomly selected from participating sites and recruited at routine visits. A biorepository of blood samples was created and comprehensive demographic and clinical outcome data were entered in a centralized electronic database. Peripheral blood genome-wide single nucleotide polymorphism (SNP) genotyping was performed using a customized Transfusion Medicine (TM) Array. A total of 2795 participants at six Brazilian sites were enrolled between 2013 and 2015. The cohort included slight predominance of children <18 years (55·9%) and females (53·0%). Haemoglobin (Hb) SS was the most common SCD genotype (70·7%), followed by HbSC (23%), Sβ0 (3·0%) and Sβ+ (2·9%). SNP data from the TM Array were analysed to evaluate the genetic ancestry of the cohort and revealed significant admixture among the population. Demographics and clinical complications, stratified by age and SCD genotype, are summarized and future studies in this cohort are discussed.

Red blood cell exchange in patients with sickle cell disease-indications and management: a review and consensus report by the therapeutic apheresis subsection of the AABB

BACKGROUND

A prior practice survey revealed variations in the management of patients with sickle cell disease (SCD) and stressed the need for comprehensive guidelines. Here we discuss: 1) common indications for red blood cell exchange (RCE), 2) options for access, 3) how to prepare the red blood cells (RBCs) to be used for RCE, 4) target hemoglobin (Hb) and/or hematocrit (Hct) and HbS level, 5) RBC depletion/RCE, and 6) some complications that may ensue.

STUDY DESIGN AND METHODS

Fifteen physicians actively practicing apheresis from 14 institutions representing different areas within the United States discussed how they manage RCE for patients with SCD.

RESULTS

Simple transfusion is recommended to treat symptomatic anemia with Hb level of less than 9 g/dL. RCE is indicated to prevent or treat complications arising from the presence of HbS. The most important goals are reduction of HbS while also preventing hyperviscosity. The usual goals are a target HbS level of not more than 30% and Hct level of less than 30%.

CONCLUSION

Although a consensus as to protocol details may not be possible, there are areas of agreement in the management of these patients, for example, that it is optimal to avoid hyperviscosity and iron overload, that a target Hb S level in the range of 30% is generally desirable, and that RCE as an acute treatment for pain crisis in the absence of other acute or chronic conditions is ordinarily discouraged.

Sickled erythrocytes in urine as a clue to the diagnosis of sickle cell trait

Sickled erythrocytes in patients of sickle cell trait with microscopic hematuria have rarely been reported so far. A 30-year-old female underwent delivery of a healthy full-term baby by cesarean section. However, postcesarean, she had pain in abdomen and fever, for which she was advised blood and urine examination. The hemogram suggested mild leukocytosis with neutrophilia and the urine showed red blood cells, some of which were sickled. The patient was advised hemoglobin electrophoresis which suggested sickle cell trait (Hb-AS). We conclude that sickled erythrocytes should not be ignored in a sample of urine as it may serve as an important clue to the diagnosis of sickle cell trait or disease.

Evaluation of the V8 E-Class, a Novel Automated Capillary Isoelectric Focusing Instrument for Hemoglobinopathy Screening

OBJECTIVES

We evaluated the performance of a novel capillary isoelectric focusing (CIEF) application for hemoglobinopathy screening on the recently introduced V8 E-Class platform.

METHODS

Analytical performance of the V8 E-Class was evaluated and included assessment of hemoglobin A2 (HbA2) imprecision; linearity for HbA2, fetal hemoglobin (HbF), and sickle hemoglobin (HbS); and carryover for HbS. Furthermore, a method comparison with the Minicap Flex Piercing (Sebia, Lisses, France), the Variant Classic (Bio-Rad Laboratories, Hercules, CA), and the G8 (Tosoh Europe, Amsterdam, the Netherlands) was done to assess analytical and clinical concordance.

RESULTS

Total HbA2 imprecision was 3.26% and 3.14% for normal and elevated HbA2 controls and 5.16% and 3.58% for a normal and a heterozygous HbS patient sample, respectively. HbA2, HbF, and HbS showed acceptable linearity, and no carryover was observed. The method comparison showed good analytical concordance (r > 0.95) except for a homozygous HbS subset (r = 0.532-0.704). A comparable phenomenon was seen for the clinical concordance with good agreement in samples without variants (weighted κ > 0.80) but poorer agreement in HbS samples (κ < 0.30).

CONCLUSIONS

Good analytical performance was demonstrated for this novel CIEF application for hemoglobinopathy screening. Method comparison showed generally good correlation but highlights the need for standardization. Finally, software optimization could further add to its use for routine hemoglobinopathy screening.

Sickle Cell Trait, Rhabdomyolysis, and Mortality among U.S. Army Soldiers

BACKGROUND

Studies have suggested that sickle cell trait elevates the risks of exertional rhabdomyolysis and death. We conducted a study of sickle cell trait in relation to these outcomes, controlling for known risk factors for exertional rhabdomyolysis, in a large population of active persons who had undergone laboratory tests for hemoglobin AS (HbAS) and who were subject to exertional-injury precautions.

METHODS

We used Cox proportional-hazards models to test whether the risks of exertional rhabdomyolysis and death varied according to sickle cell trait status among 47,944 black soldiers who had undergone testing for HbAS and who were on active duty in the U.S. Army between January 2011 and December 2014. We used the Stanford Military Data Repository, which contains comprehensive medical and administrative data on all active-duty soldiers.

RESULTS

There was no significant difference in the risk of death among soldiers with sickle cell trait, as compared with those without the trait (hazard ratio, 0.99; 95% confidence interval [CI], 0.46 to 2.13; P=0.97), but the trait was associated with a significantly higher adjusted risk of exertional rhabdomyolysis (hazard ratio, 1.54; 95% CI, 1.12 to 2.12; P=0.008). This effect was similar in magnitude to that associated with tobacco use, as compared with no use (hazard ratio, 1.54; 95% CI, 1.23 to 1.94; P<0.001), and to that associated with having a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of 30.0 or more, as compared with a BMI of less than 25.0 (hazard ratio, 1.39; 95% CI, 1.04 to 1.86; P=0.03). The effect was less than that associated with recent use of a statin, as compared with no use (hazard ratio, 2.89; 95% CI, 1.51 to 5.55; P=0.001), or an antipsychotic agent (hazard ratio, 3.02; 95% CI, 1.34 to 6.82; P=0.008).

CONCLUSIONS

Sickle cell trait was not associated with a higher risk of death than absence of the trait, but it was associated with a significantly higher risk of exertional rhabdomyolysis. (Funded by the National Heart, Lung, and Blood Institute and the Uniformed Services University of the Health Sciences.).

Cardiopulmonary Bypass without Preoperative Exchange Transfusion in Sicklers

The effect of hypothermic cardiopulmonary bypass techniques on the sickling process was evaluated in patients with sickle cell hemoglobin. It was presumed that intraoperative hemolysis, as identified by hemoglobinuria, reflected increased sickling. Data of 43 patients with sickle cell traits and 2 with sickle cell disease, who were operated on under cardiopulmonary bypass and cold cardioplegic arrest in a tertiary center from the beginning of 1995 to the end of 2004, were retrospectively analyzed. A mean nasal temperature of 30.8°C ± 2.1°C was achieved. Three patients with sickle cell trait developed intraoperative hemoglobinuria, albeit with normal surrogate values for hemolysis. However, they had significantly lower mean hemoglobin levels during cardiopulmonary bypass compared to those sickle cell patients who did not exhibit hemoglobinuria (hemoglobin, 6.0 ± 0.2 vs. 7.4 ± 0.9 g·dL−1, p < 0.01). Total drainage and blood transfusion requirements in patients with normal and sickle cell hemoglobin were similar. It was concluded that hypothermic cardiopulmonary bypass with cold cardioplegia is safe in sickle cell patients. Maintenance of adequate hemoglobin levels during cardiopulmonary bypass may be important to avoid triggering a sickling process.

Screening for sickle cell disease on dried blood: a new approach evaluated on 27,000 Belgian newborns

Setting: Early diagnosis of sickle cell disease decreases morbidity. However, cost-effective screening programmes are not yet available.

Methods: We explored the feasibility of systematic screening performed on dried blood harvested from five-day-old newborns.

Results: A total of 27,010 samples were collected in Belgian maternity units between June 2003 and February 2005, and the presence of haemoglobin (Hb) C or S in the eluted blood was examined by an enzyme-linked immunosorbent assay (ELISA) test performed with a monoclonal antibody detecting both mutated forms. As this antibody slightly cross-reacts with Hb A, better specificity is achieved if the test is performed not later than day 5. Among the 27,010 samples, 132 (0.49%) were positive. Molecular biology tests performed on dried blood from positive samples showed that 106 of these babies were heterozygotes for the Hb S mutation and three were heterozygotes for the Hb C mutation, while three newborns were SS homozygotes (0.011%). Seventeen samples (0.063%) were false-positives as we could not detect any mutation.

Conclusions: We have developed a new immunological approach in the field of haemoglobinopathy neonatal screening. This ELISA test is cheap (€0.2/test or €1800/detected SS homozygote) and could be centralized. Its cost-effectiveness in the whole Belgian population is comparable with that of screening for phenylketonuria or congenital adrenal hyperplasia. Further improvements should obviously be achieved in order to better discriminate heterozygotes and homozygotes, but the accessibility and the low cost of the test are relevant arguments for the screening extension in a wide range of countries, especially in Central Africa.

Screening for Structural Hemoglobin Variants in Bahia, Brazil

Brazil was the country that received the largest number of Africans during the time of colonization, and Bahia was the Brazilian state that received the largest number of slaves from Africa. The purpose of this study was to evaluate the coverage of the newborn screening program for sickle cell disease in the Recôncavo Baiano region of the state of Bahia, and to show the frequency of the subjects with hemoglobin variants in the 2006–2009 period. Blood samples from neonates in twelve cities in the Recôncavo Baiano region were analyzed by High Performance Liquid Chromatography. A total of 16,402 children were born in this period, 14,773 of which underwent newborn screening. In this period 1416 children were born carrying hemoglobin variants HbS and HbC. Forty-seven patients—20 HbSS genotype and 27 HbSC genotype—were diagnosed in eleven of the twelve cities surveyed. The proportion of children born with sickle cell disease in the Recôncavo Baiano region was 1/314, which was higher than the 1/650 rate for the state of Bahia. The data presented in this study confirm the high frequency of sickle cell disease in Recôncavo Baiano, demonstrating the need to create a referral center for the care of patients with sickle cell diseases in the region.

Sickle Cell Imaging Flow Cytometry Assay (SIFCA)

Hemoglobin S polymerization under hypoxic conditions in sickle cell disorders causes characteristic shape changes to human red blood cells. Previous sickling assays used to investigate the efficacy of novel agents to treat these disorders are laborious and observer dependent. Here, we describe a partially automated, high-throughput sickling assay using imaging flow cytometry.

[Susceptibility of induced sickle in samples of heterozygous hemoglobin S patients (sickle cell trait) suffering diabetes mellitus type 2]

Hemoglobin S is an abnormal protein that induces morphological changes in erythrocyte in low-oxygen conditions. In Mexico, it is reported that up to 13.7% of the population with mutation in one allele are considered asymptomatic (sickle cell trait). The sickle cell trait and diabetes mellitus are conditions that occur together in more than one million patients worldwide. Both diseases possibly produce microvascular changes in retinopathy and acute chest syndrome. The aim of this study was to evaluate the induction of sickle cells in samples of diabetic patients with sickle cell trait to identify altered red cell parameters. We obtained samples of diabetic patients to determine hemoglobin A1c and S; furthermore, red blood cell biometrics data were analyzed. We found that older men with diabetes were susceptible to generate sickle cells and this correlated with reduced red blood cell count and an increase in media cell volume. In samples of women diabetes, there were no differences. We conclude that samples from patients with sickle cell trait and diabetes can cause sickle cells with high frequency in men, with lower red blood cells count and increased mean corpuscular volume as susceptibility parameters.

Impact of sickle cell trait on the thrombotic risk associated with non-O blood groups in northern Nigeria

BACKGROUND

The non-O blood group is an established risk factor for deep vein thrombosis (DVT), while controversy surrounds the role of sickle cell trait (SCT) as a risk factor for DVT. We hypothesised that if SCT is a risk factor for DVT, individuals with non-O blood groups and SCT (Hb AS) would have a higher risk of DVT than their counterparts with non-O blood groups and normal haemoglobin phenotype (Hb AA).

MATERIALS AND METHODS

We retrospectively analysed the prevalence of SCT and non-O blood groups among 148 DVT patients with control subjects in order to determine the role of SCT as a risk factor for DVT and its impact on the risk of DVT among patients with non-O blood groups.

RESULTS

In comparison with control subjects, DVT patients had significantly higher prevalences of SCT (35.1% vs 27.7%, p=0.04) and non-O blood groups (68.9% vs 45.9%, p=0.02). The odds ratios for DVT due to SCT, non-O blood groups with normal Hb phenotype (Hb AA) and non-O blood groups with SCT (Hb AS) were 1.3, 2.4 and 3.5, respectively.

DISCUSSION

These results suggest that SCT by itself is a weak risk factor for DVT but it has the potential of escalating the DVT risk among patients with non-O blood groups. The combined effects of elevated clotting factors (non-O group effect) and increased clotting factor activation (SCT effect) were responsible for the escalated DVT risk among patients with co-inheritance of non-O blood groups and SCT. Co-inheritance of SCT and non-O blood group is, therefore, an important mixed risk factor for DVT. This should be taken into account when assessing DVT risk profiles of patients in Africa and other parts of the world where the SCT is prevalent.

Sickle cell trait diagnosis: clinical and social implications

The sickle hemoglobin (HbS) point mutation has independently undergone evolutionary selection at least five times in the world because of its overwhelming malarial protective effects in the heterozygous state. In 1949, homozygous Hb S or sickle cell disease (SCD) became the first inherited condition identified at the molecular level; however, since then, both SCD and heterozygous Hb S, sickle cell trait (SCT), have endured a long and complicated history. Hasty adoption of early mass screening programs for SCD, recent implementation of targeted screening mandates for SCT in athletics, and concerns about stigmatization have evoked considerable controversy regarding research and policy decisions for SCT. Although SCT is a largely protective condition in the context of malaria, clinical sequelae, such as exercise-related injury, renal complications, and venous thromboembolism can occur in affected carriers. The historical background of SCD and SCT has provided lessons about how research should be conducted in the modern era to minimize stigmatization, optimize study conclusions, and inform genetic counseling and policy decisions for SCT.

Hemoglobin Variants Acquired Post-Exchange Transfusion in Pediatric Sickle Cell Disease (SCD) Patients

BACKGROUND

Many SCD patients receive chronic transfusions for prevention or treatment of disease related complications. Complications of the chronic transfusion noted in these patients include allergic reactions, transfusion transmitted infections, iron overload, and alloantibody formation. Even though hemoglobin (Hb) variants are prevalent in the general population, reports of transfusion-acquired Hb variants are rare. We performed a retrospective analysis on all SCD patients who underwent red cell exchange (RBCEx) transfusions at our institution during 2011-2013 to identify the presence of Hb variants acquired as a result of RBCEx.

RESULTS

We found 66 occurrences of acquired Hb variants in 30 SCD patients during the period examined. The most commonly acquired Hb variant was Hemoglobin C (HbC) (64/66 occurrences). More than half of the patients (19/30) acquired HbC on multiple occasions (2-6 times). One patient acquired HbJ and another patient acquired HbD/G in addition to HbC. The segments from donor units were available in some of these cases and hemoglobin electrophoresis (HBE) was performed to confirm the presence of the variant Hb in the donor segments corresponding to that seen on the post-RBCEx sample.

CONCLUSIONS

Heterozygous donors are asymptomatic and show no abnormalities during donor screening. Since HBE is not routinely performed on the donor specimen, it may go unrecognized until the post-transfusion recipient results pose diagnostic difficulties. There are no definitive guidelines on deferring these donors; hence one should be cognizant of these findings to prevent misdiagnosis. In a population where HbS negative blood is routinely requested, the effect of other Hb variants remains unknown. None of the patients in our study showed any adverse events due to the acquired Hb variants; however, this is of special concern in the pediatric population where a single RBC unit can contribute a significant portion of the exchanged blood volume. Additionally, donor centers may need mechanisms to confirm the findings and counsel the donors as needed.

Controlled trial of transfusions for silent cerebral infarcts in sickle cell anemia

BACKGROUND

Silent cerebral infarcts are the most common neurologic injury in children with sickle cell anemia and are associated with the recurrence of an infarct (stroke or silent cerebral infarct). We tested the hypothesis that the incidence of the recurrence of an infarct would be lower among children who underwent regular blood-transfusion therapy than among those who received standard care.

METHODS

In this randomized, single-blind clinical trial, we randomly assigned children with sickle cell anemia to receive regular blood transfusions (transfusion group) or standard care (observation group). Participants were between 5 and 15 years of age, with no history of stroke and with one or more silent cerebral infarcts on magnetic resonance imaging and a neurologic examination showing no abnormalities corresponding to these lesions. The primary end point was the recurrence of an infarct, defined as a stroke or a new or enlarged silent cerebral infarct.

RESULTS

A total of 196 children (mean age, 10 years) were randomly assigned to the observation or transfusion group and were followed for a median of 3 years. In the transfusion group, 6 of 99 children (6%) had an end-point event (1 had a stroke, and 5 had new or enlarged silent cerebral infarcts). In the observation group, 14 of 97 children (14%) had an end-point event (7 had strokes, and 7 had new or enlarged silent cerebral infarcts). The incidence of the primary end point in the transfusion and observation groups was 2.0 and 4.8 events, respectively, per 100 years at risk, corresponding to an incidence rate ratio of 0.41 (95% confidence interval, 0.12 to 0.99; P=0.04).

CONCLUSIONS

Regular blood-transfusion therapy significantly reduced the incidence of the recurrence of cerebral infarct in children with sickle cell anemia. (Funded by the National Institute of Neurological Disorders and Stroke and others; Silent Cerebral Infarct Multi-Center Clinical Trial ClinicalTrials.gov number, NCT00072761, and Current Controlled Trials number, ISRCTN52713285.).

Newborn screening for haemoglobinopathies by high performance liquid chromatography (HPLC): diagnostic utility of different approaches in resource-poor settings

BACKGROUND

Sickle cell disease is a major health burden in India. The aim of the study was to compare the diagnostic utility of two different approaches on automated high performance liquid chromatography (HPLC) for newborn screening for sickle cell disorders and other haemoglobinopathies in India.

METHODS

Newborn babies of sickle heterozygous mothers were tested by HPLC using two different kits, the β-thal short kit, which is routinely used for screening for haemoglobinopathies in most laboratories, and the sickle cell short kit which is specific only for neonatal samples. Confirmation of the sickle and α genotypes was done by molecular analysis.

RESULTS

Of the 601 babies tested, 276 were normal, 284 were sickle heterozygous and 41 were sickle homozygous using the β-thal short kit. Using the sickle cell short kit, a discrepancy was seen in one newborn sample where a normal baby was identified as a sickle heterozygous baby. α-Genotyping was done in 42 babies and 16 of them had α gene deletions. The presence of α thalassaemia could be suspected in 15 of these 16 babies based on a spike at the start of the chromatogram using the β-thal short kit. In comparison, using the sickle cell short kit the diagnosis of α thalassaemia was difficult based on the percentage of the FAST peak. Further, other rare α chain Hb variants were also missed.

CONCLUSIONS

The β-thal short kit was more versatile than the sickle cell short kit for screening for haemoglobinopathies in newborns in our population.

A prospective newborn screening and treatment program for sickle cell anemia in Luanda, Angola

Over 300,000 infants are born annually with sickle cell anemia (SCA) in sub-Saharan Africa, and >50% die young from infection or anemia, usually without diagnosis of SCA. Early identification by newborn screening (NBS), followed by simple interventions dramatically reduced the mortality of SCA in the United States, but this strategy is not yet established in Africa. We designed and implemented a proof-of-principle NBS and treatment program for SCA in Angola, with focus on capacity building and local ownership. Dried bloodspots from newborns were collected from five birthing centers. Hemoglobin identification was performed using isoelectric focusing; samples with abnormal hemoglobin patterns were analyzed by capillary electrophoresis. Infants with abnormal FS or FSC patterns were enrolled in a newborn clinic to initiate penicillin prophylaxis and receive education, pneumococcal immunization, and insecticide-treated bed nets. A total of 36,453 infants were screened with 77.31% FA, 21.03% FAS, 1.51% FS, and 0.019% FSC. A majority (54.3%) of affected infants were successfully contacted and brought to clinical care. Compliance in the newborn clinic was excellent (96.6%). Calculated first-year mortality rate for babies with SCA compares favorably to the national infant mortality rate (6.8 vs. 9.8%). The SCA burden is extremely high in Angola, but NBS is feasible. Capacity building and training provide local healthcare workers with skills needed for a functional screening program and clinic. Contact and retrieval of all affected SCA infants remains a challenge, but families are compliant with clinic appointments and treatment. Early mortality data suggest screening and early preventive care saves lives.

Novel test method (sickle confirm) to differentiate sickle cell anemia from sickle cell trait for potential use in developing countries

The objective of this study was to develop a diagnostic testing method to detect HbS, distinguish sickle cell homozygotes from heterozygotes, and overcome testing barriers encountered in laboratories in underdeveloped countries. Blood samples positive and negative for sickle cell were subjected to the standard hemoglobin solubility test followed by a variety of centrifugation and filtration procedures. Each procedure was evaluated for the ability to remove insoluble HbS from the sample. The hemoglobin types that remain (HbA, HbA2 and HbF) were measured spectrophotometrically or estimated visually allowing samples to be categorized into three genotypes (AA, AS and SS) as confirmed by hemoglobin electrophoresis. De-identified EDTA blood samples were obtained from Saint Louis University and Cardinal Glennon Children's hospitals and tested in the Department of Clinical Laboratory Science at Saint Louis University. The main outcome measures were turbidity of the solubility solution; color of the supernatant and the material on the surface of the solution following centrifugation; precipitate trapped on the filter paper; absorbance of the filtrate; and hemoglobin electrophoresis patterns. Centrifugation and filtration successfully separated HbS from HbA/A2/F allowing for the differentiation of seven sickle cell homozygotes from sixteen heterozygotes with a sensitivity and specificity of 100%. This method has the potential to reliably distinguish homozygous from heterozygous sickle cell patients and it is fast, inexpensive, and simple. These characteristics make Sickle Confirm a desirable method in developing countries like Haiti and Africa where sickle cell anemia is prevalent and modern diagnostic methods like electrophoresis, HPLC and nucleic acid testing are impractical.

Does elevated hemoglobin F modulate the phenotype in Hb SD-Los Angeles?

Hemoglobin (Hb) SD-Los Angeles compound heterozygotes usually have a severe clinical course although the effect of an elevated Hb F on the clinical phenotype has not been reported previously. We describe 5 Kuwaiti children with Hb SD associated with Hb F levels >20%. They all presented with sickling-related symptoms by < or =2 years of age and have been followed for 3-15 years. All had severe clinical courses marked by varying degrees of splenic sequestration crises, acute chest syndrome, vaso-occlusive crises, osteomyelitis and avascular necrosis of the femoral head. This pattern is in contrast with the usually mild presentation in Kuwaiti Hb SS patients with elevated Hb F. It therefore appears that Hb F does not ameliorate the clinical phenotype in Hb SD-Los Angeles. The reasons for this are not quite clear.

Estimated prevalence of sickle cell in northern Haiti

OBJECTIVE

The purpose of this study is to estimate the prevalence of sickle hemoglobin in northern Haiti.

DESIGN

Sickle cell testing occurred from 2002-2009. Blood samples from 1035 subjects were collected for diagnostic purposes, de-identified, and made available for the study.

SETTING

Bethesda Medical Center and Eben-Ezer Clinic in northern Haiti.

SUBJECTS

Study subjects included prenatal patients, their companions, clinic staff and volunteers. All subjects were Haitian and selected to most closely represent healthy patients present at the clinic. Deidentification of the blood samples precluded the need for informed consent.

MAIN OUTCOME MEASURES

Each subject was tested for sickle hemoglobin using a standard hemoglobin solubility test and results were recorded as either positive or negative.

RESULTS

The estimated prevalence of sickle hemoglobin was 15.1% with a 95% confidence interval of 12.2-18%.

CONCLUSIONS

These prevalence rates validate the clinical significance of sickle cell disorder, help guide clinical decisions, and suggest the need to develop intervention programs among the people of northern Haiti.

Effects of a single sickling event on the mechanical fragility of sickle cell trait erythrocytes

Hemolysis contributes to the pathology associated with sickle cell disease. However, the mechanism of hemolysis or relative contribution of sickling due to hemoglobin (Hb) polymerization vs. oxidative damage remains unknown. Earlier studies aimed at deciphering the relative importance of these two mechanisms have been complicated by the fact that sickle red cells (SS) have already been affected by multiple rounds of sickling and oxidative damage before they are collected. In our study, we examine the mechanical fragility of sickle cell trait cells, which do not sickle in vivo, but can be made to do so in vitro. Thus, our novel approach explores the effects of sickle Hb polymerization on cells that have never been sickled before. We find that the mechanical fragility of these cells increases dramatically after a single sickling event, suggesting that a substantial amount of hemolysis in vivo probably occurs in polymer-containing cells.

[Knowledge of sickle cell disease and prevention methods in an urban district of Lomé, Togo]

Despite the important frequency of the gene "S" in Togo, essential information remains insufficient to elaborate a prevention campaign on this affection. In order to assess the knowledge on sickle cell diseases as well as the prevention practices in the Togo population in one of the five districts of the township of Lomé, a cross sectional study was conducted in the third district of the township of Lomé from January 21, 2004 to January 26, 2004 in 210 natives from Togo aged of 15 and over, through a semi-structured questionnaire. The variables studied were: - the socio-demographic features and the knowledge of sickle cell disease characteristics (symptoms, biological diagnosis, treatment and means). Data collected were analysed through software Statically Package for Social Science (SPSS) version 10.0 of Windows using the chi2 test with 5% significance in the comparison of some variables. 117 women and 93 men were interviewed. Sickle cell disease was known in almost all ethnic groups but incompletely: 79.5% of the individuals knew about premarital check up but only 12.4% knew about haemoglobin electrophoresis check up. 74,8% of the people had a good knowledge of the cause of sickle cell disease, 78.6% had a fairly good knowledge of its symptoms, 57.6% knew the factors inducing attacks, 64.3% the prognosis and 69.5% the prevention methods, but a poor knowledge of the complications (62.4%), biological diagnosis (71%) and treatment (97.2%). The prevention practices were poorly adopted: 12% had an haemoglobin electrophoresis check up and 15% of them had their husband to have one as well. Professional status influenced the level of knowledge of the biological diagnosis (p=0.001) and prevention means (p=0.018). The educational level influenced biological diagnosis knowledge (p = 0.000) and prevention means (p = 0.02). On the whole, sickle disease was linked to marital status (p = 0.00). Sickle cell disease remains quite unknown in spite of the gene "S" important frequency in Togo. These results are to be taken into account to implement information, education and communication program to struggle against sickle cell disease.

Rapid quantitation of hemoglobin S in sickle cell patients using the Variant II Turbo analyzer

A rapid ( approximately 90 sec), fully automated method is described for quantifying hemoglobin S (HbS) by high performance liquid chromatography (HPLC) using the Bio-Rad Variant II Turbo analyzer. Although this instrument is designed to quantify only blood hemoglobin A1c (HbA1c), we show that it can also quantify accurately, without modification, HbS levels in sickle cell patients, provided the blood samples meet certain conditions. The samples should contain detectable hemoglobin F (HbF), but should not contain hemoglobin C (HbC). Under these conditions, blood HbS levels obtained by this method correlate well with those obtained by agarose electrophoresis (r(2) = 0.97, n = 81 patients). We also show that quantitation of blood HbF in sickle cell patients is more accurate by this method than by agarose electrophoresis when the HbF level is in the range from 0.2 to 10%.

Mitral valve replacement in a patient with sickle cell disease using perioperative exchange transfusion

Sickle cell disease is a genetic hemoglobinopathy in which a significant number of red blood cells carry hemoglobin-S as opposed to normal red blood cells that contain hemoglobin-A. Under certain conditions such as hypoxia, acidosis, and hypothermia, the red blood cells containing hemoglobin-S will sickle, leading to occlusion of the microvasculature. As such, patients with sickle cell disease present unique challenges during heart surgery using cardiopulmonary bypass (CPB). After conducting a literature review, we discovered that the exact hemoglobin-S level for conducting cardiac surgery with CPB is not known. However, a hemoglobin-S level < 30% is considered safe for conducting CPB. The following case report will discuss these challenges and present a patient with sickle cell disease undergoing a mitral valve repair. Management of this patient involved exchange transfusions both preoperatively and intraoperatively.

High prevalence of Plasmodium falciparum Pfmdr1 86Y mutant gene in sickle cell disease in Nigeria

BACKGROUND AND PURPOSE

In areas where malaria is endemic, drug prophylaxis is required for people with sickle cell disease. Chloroquine resistance has been associated with the Plasmodium falciparum multidrug resistance 1 (Pfmdr1) mutant gene. This study tested for the Pfmdr1 86Y mutation in P. falciparum isolates from individuals with sickle cell disease and sickle cell trait, who also underwent hemoglobin genotyping.

METHODS

Blood samples were collected from patients presenting with symptoms of malaria in an endemic region. The subjects were screened for hemoglobin genotype using hemoglobin electrophoresis and P. falciparum Pfmdr1 genotyping was carried out using polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

229 subjects, comprising 144 with hemoglobin AA genotype, 57 with hemoglobin AS genotype and 28 with hemoglobin SS genotype, were enrolled in this study. There was no significant difference in the infective rate of malaria in the 3 groups (p>0.05). However, the prevalence of Pfmdr1 86Y was higher in those with hemoglobin SS genotype than in hemoglobin AA and AS subjects (p<0.05).

CONCLUSIONS

Uncontrolled use of chloroquine is a major cause of chloroquine resistance in Nigeria. Chloroquine prophylaxis may be the underlying cause of the high prevalence of Pfmdr1 86Y mutant gene in individuals with hemoglobin SS genotype.

Quantitative analysis of Howell-Jolly bodies in children with sickle cell disease

OBJECTIVES

Although functional asplenia in sickle cell disease (SCD) begins early in life and has important clinical consequences, quantitative measurement of splenic function is not readily available. A novel high-throughput flow cytometric method for quantitating Howell-Jolly bodies (HJB) has been developed which isolates HJB-containing CD71(+) and CD71(-) erythrocytes. Analysis of these cell populations allows quantitative measurement of splenic filtrative function and possible chromosomal damage.

METHODS

Blood specimens from 147 children with SCD were analyzed using a high-throughput flow cytometric method. Enumeration of the following populations was accomplished: 1) CD71(+) reticulocytes among total erythrocytes, identifying the youngest erythroid cell population; 2) HJB-containing CD71(+) reticulocytes, which isolate young erythrocytes containing micronuclei as an index of cytogenetic damage; and 3) HJB-containing CD71(-) erythrocytes, identifying older erythrocytes containing micronuclei, indirectly measuring splenic function.

RESULTS

Children with HbSC (n = 24) had slightly elevated HJB frequencies, while children with HbSS (n = 125) had highly elevated frequencies within CD71(+) cells (0.44% +/- 0.40%, normal 0.12% +/- 0.06%, p < 0.001) and CD71(-) cells (2493 +/- 2303 per million RBC, normal 20 +/- 11, p < 0.001). Using a multiple regression model, the frequency of HbSS CD71(+) reticulocytes containing HJB was significantly influenced by hydroxyurea use (p < 0.0001), age (p = 0.0288), and splenectomy (p = 0.0498). Similarly, mature CD71(-) erythrocytes containing HJB were positively correlated with hydroxyurea (p = 0.0001), age (p < 0.0001), and splenectomy (p = 0.0104).

CONCLUSIONS

HJB quantitation by flow cytometry is a novel assay for measuring splenic function and may be valuable for investigating the efficacy and safety of therapeutic options for children with SCD.

[Chronic osteomyelitis at the Ouagadougou teaching hospital (Burkina Faso). A retrospective study of 102 cases (1996-2000)]

This is a retrospective study carried out in the orthopaedic and trauma department of the Yalgado-Ouédraogo teaching hospital. All the patients hospitalized in the service with a chronic osteomyelitis (COM) from March 1, 1996 to March 28, 2000 were included. The frequency of COM was 5.3%. The patients' average age was 17.7 with extremes of 2 and 60 years old. 63.9% were male; 80.7% had fistulized COM. A pathological fracture was observed in 16.9% of the patients. Lower limbs were affected most frequently (65%). Thirty patients (36.1%) had haemoglobin S, among them 22 had a major sickle cell disease. Staphylococcus aureus was present in the majority of the cases (more than 50%). Salmonella were observed among patients carrying haemoglobin S. One case of ceftriaxone-resistance salmonella osteomyelitis was reported. The medico-surgical and orthopaedic treatment was statistically more favourable than a medical or medico-surgical treatment without immobilization.

[Evaluation of coverage by a neonatal screening program for hemoglobinopathies in the Recôncavo region of Bahia, Brazil]

In 2001, government ruling n. MS 822/01 by the Brazilian Ministry of Health made neonatal screening mandatory for hemoglobinopathies, with special focus on sickle cell disease, the most common hemoglobinopathy in Brazil. Bahia is the State of Brazil with the highest prevalence of this disease. The current paper reports on the prevalence of hemoglobin variants HbS and HbC, which cause sickle cell disease, in the cities of Cachoeira, Maragogipe, and São Félix, Bahia State. The overall proportion of carriers for the two forms of hemoglobin was 13%. From 2001 to 2003, the neonatal screening rate decreased from 82.6% to 46.4% in Cachoeira and increased from 37.0% to 56.2% in Maragogipe. Thus, only about one-half of children are being tested in these cities. The findings show that the public health care system in these cities is poorly prepared to screen for sickle cell disease in newborns and that there was a lack of health care personnel to follow up on newly diagnosed sickle cell patients or carriers of the sickle cell trait.

Hemoglobin variants and disease manifestations in severe falciparum malaria

CONTEXT

The geographical distributions of hemoglobin S (HbS), hemoglobin C (HbC), and alpha+-thalassemia (-alpha) strongly suggest balancing selection with malaria. However, whereas several studies indicate that the HbS carrier state protects against all major forms of clinical malaria, malaria protection on clinical grounds has been more difficult to confirm for HbC and -alpha, and questions remain as to whether it applies to all forms of the disease.

OBJECTIVE

To assess the association between major clinical forms of severe falciparum malaria and HbS, HbC, and -alpha.

DESIGN, SETTING, AND PARTICIPANTS

Case-control study of 2591 children with severe falciparum malaria enrolled at a tertiary referral center in Ghana, West Africa, and 2048 age-, sex-, and ethnicity-matched control participants recruited by community surveys.

MAIN OUTCOME MEASURES

Frequencies of HbS, HbC, and -alpha in patients and controls, including stratifications of patients for signs of disease.

RESULTS

Patients presented with partly overlapping signs of disease, including severe anemia (64%), cerebral malaria (22%), respiratory distress (30%), hyperparasitemia (32%), prostration (52%), acidosis (59%), and hyperlactatemia (56%). Carrier states of HbS, HbC, and -alpha were found in 1.4%, 9.4%, and 25.2% of the patients, respectively, and 14.8%, 8.7%, and 27.3% of controls. The HbS carrier state was negatively associated with all forms of the disease studied (overall odds ratio [OR], 0.08; 95% confidence interval [CI], 0.06-0.12). The HbC carrier state showed a negative association selectively with cerebral malaria (OR, 0.64; 95% CI, 0.45-0.91), and the -alpha carrier state showed a negative association selectively with severe anemia (OR, 0.82; 95% CI, 0.69-0.96).

CONCLUSION

Whereas the HbS carrier state was found to be negatively associated with all major forms of severe falciparum malaria, the negative associations of the carrier states of HbC and -alpha appeared to be limited to cerebral malaria and severe anemia, respectively.

Sickle cell trait and the risk of venous thromboembolism among blacks

People with sickle cell disease have a chronically activated coagulation system and display hemostatic perturbations, but it is unknown whether they experience an increased risk of venous thromboembolism. We conducted a case-control study of venous thromboembolism that included 515 hospitalized black patients and 555 black controls obtained from medical clinics. All subjects were assayed for hemoglobin S and hemoglobin C genotypes. The prevalence of the S allele was 0.070 and 0.032 for case patients and controls, respectively (P < .001). The odds that a patient had sickle cell trait were approximately twice that of a control, indicating that the risk of venous thromboembolism is increased approximately 2-fold among blacks with sickle cell trait compared with those with the wild-type genotype (odds ratio = 1.8 with 95% confidence interval, 1.2-2.9). The odds ratio for pulmonary embolism and sickle cell trait was higher, 3.9 (2.2-6.9). The prevalence of sickle cell disease was also increased among case patients compared with controls. We conclude that sickle cell trait is a risk factor for venous thromboembolism and that the proportion of venous thromboembolism among blacks attributable to the mutation is approximately 7%.

Effects of hydroxyurea and L-arginine on the production of nitric oxide metabolites in cultures of normal and sickle erythrocytes

Previous in vitro studies suggest that erythrocytes may be a source of nitric oxide (NO) produced by nitric oxide synthase (NOS) or by oxyhemoglobin-mediated oxidation of hydroxyurea (HU). This study was performed to determine the roles of HU and NOS in the production of NO by normal and sickle erythrocytes. Red blood cells (RBCs) from normal adult hemoglobin (HbAA) and homozygous sickle cell subjects (HbSS) were incubated with PBS containing 0.2 mM hydrogen peroxide (control) for 2 h at 37 degrees C in the presence and absence of l-arginine, the substrate for NOS, and with l-arginine plus HU in the presence and absence of l-NMMA, a specific inhibitor of NOS. The nitrate and nitrite metabolites of NO, expressed as [NOx], were measured. [NOx] in the HbAA and HbSS RBC cultures was not significantly different in the presence and absence of 1.0 mM l-arginine (p>0.1). [NOx] in the HbAA and HbSS cultures treated with a clinically relevant dose of HU (1.0 mM) plus 1.0 mM l-arginine was significantly greater than that in controls incubated with PBS and with l-arginine p < 0.01. However, [NOx] in the HbAA and HbSS cultures treated with 50 microg/ml l-NMMA was not significantly different than that in the cultures treated with HU plus l-arginine in the absence of l-NMMA. These findings suggest that NOx production by erythrocytes may be increased by treatment with HU and may not be decreased by inhibiting NOS. Therefore, we conclude that a therapeutic dose of HU may increase the plasma concentration of NO by a mechanism that does not require erythrocytes NOS activity.

Blood bank issues associated with red cell exchanges in sickle cell disease

Sickle cell disease (SCD) patients are prone to develop complications that include stroke, acute chest syndrome, and other crises. Some of these complications require chronic transfusion therapy or red cell exchange (RCE), either for therapeutic or prophylactic reasons. Due to a discrepancy of red cell antigens between African Americans and Caucasians (majority blood donors), the incidence of alloantibody formation is very high, which makes it difficult to find compatible red cell units, especially for urgent RCE. Some of the above conditions require immediate oxygen delivery to the tissues. Thus, SCD patients undergoing RCE should receive red blood cells with special attributes that include matching for Rh and Kell blood group antigens; RBCs should be fresh in order to provide (1) immediate oxygen delivery and (2) longer surviving cells to reduce the interval between RCE. Also, these units should be pre-storage leukoreduced to prevent febrile non-hemolytic reactions and screened for sickle cell traits to avoid transfusing red cells containing HbS. This requires a concerted effort between the apheresis unit, the local blood bank, and the central blood supplier.

Effect of HbS in the determination of HbA2 with the TOSOH HLC-723G7 analyzer and the HELENA Beta-Thal Quik column kit

OBJECTIVES

The analytical performance of the TOSOH HLC-723G7 hemoglobin HPLC analyzer and the effect of the presence of HbS in the determination of HbA(2) using HPLC and manual column methods.

DESIGN AND METHODS

The performance characteristics of the TOSOH HLC-723G7 analyzer in the determination of HbA(2) were compared to those of the HELENA Beta-Thal Quik column. The effect of HbS presence in the samples was quantified using the HELENA SAS-MX alkaline gel electrophoresis kit as the reference method.

RESULTS

Within-run and between-run CVs for HbA(2) were better for the TOSOH HPLC analyzer than for the HELENA manual column method. The presence of HbS in the samples produces a strong positive bias in the %HbA(2) values when using both the HPLC and manual column methods, compared to the alkaline electrophoresis gel.

CONCLUSION

Both the TOSOH HPLC and the manual column are reliable methods for %HbA(2) determination when no HbS is detectable in the samples. When HbS is present, the gel electrophoresis method gives more accurate results.

Sickle cell disease in Africa: burden and research priorities

Sickle cell disease (SCD) has recently been recognised as a problem of major public-health significance by the World Health Organization. Despite the fact that >70% of sufferers live in Africa, expenditure on the related care and research in the continent is negligible, and most advances in the understanding and management of this condition have been based on research conducted in the North. In order to target limited resources, African countries need to focus research and interventions on areas that will lead to the maximum impact. This review details the epidemiological and clinical background of SCD, with an emphasis on Africa, before identifying the research priorities that will provide the necessary evidence base for improving the management of African patients. Malaria, bacterial and viral infections and cerebrovascular accidents are areas in which further research may lead to a significant improvement in SCD-related morbidity and mortality. As patients with high concentrations of foetal haemoglobin (HbF) appear to be protected from all but mild SCD, the various factors and pharmacological agents that might increase HbF levels need to be assessed in Africa, as options for interventions that would improve quality of life and reduce mortality.

Presence of Hb S in Uttaranchal

Haemoglobin-S has been reported in several studies on remote populations from various parts of India eg Maharashtra, Madhya Pradesh, Andhra Pradesh, Orissa, West Bengal, Rajasthan and Malaysian Indians. Uttaranchal also has got scattered areas with people living in remote-pockets due to its geophysical nature. There has been no previous report from this state about prevalence of Hb-S. In the present study on 38 individual eight were found to have Hb-S positivity by sickling test. In one of these electrophoretic confirmation was positive with demonstration of associated Beta thalassaemia. The group was a family of muslims in village Baghori near Haldwani. Due to technical, geographical and social restrictions further study could not be done. However, this study does establish the presence of Hb-S-Beta thalassaemia in Uttaranchal State for the first time. Follow up study in the affected area and elsewhere in the state might discover more of Hb-S positivity, other haemoglobinopathies and thalassaemias.