Transfusion service knowledge and immunohaematological practices related to sickle cell disease and thalassemia

Objectives

To assess current knowledge of National Heart, Lung and Blood Institutes (NHLBI) and Thalassemia International Federation (TIF) recommendations, blood banking practices and perceived challenges among transfusion services in the management of patients with haemoglobinopathies.

Background

Previous reports have demonstrated variations in transfusion practices for sickle cell disease (SCD) and thalassemia patients. Recently, NHLBI/TIF have provided transfusion recommendations for patients with haemoglobinopathies.

Methods

A cross‐sectional survey was conducted of transfusion services from the state of Georgia previously identified as having SCD/thalassemia populations. The survey assessed transfusion service practices in pre‐transfusion testing and blood product selection; awareness/implementation of NHLBI/TIF transfusion‐based recommendations and perceived challenges in transfusing haemoglobinopathy patients.

Results

Responses were received from 35 of 49 (71%) institutions. Only institutions indicating transfusing SCD or thalassemia patients (32) were included in analysis. Seventy‐one percent of non‐sickle cell treatment centres (SCTCs) and 20% of non‐thalassemia treatment centres follow NHLBI and TIF recommendations to perform a red blood cell phenotype beyond ABO/Rh(D) and provide Rh and Kell prophylactically matched units for SCD and thalassemia patients, respectively. Forty percent of institutions (33% of non‐SCTCs) employ RBC genotyping to evaluate the red cell phenotype for SCD patients. Over 77% of institutions do not utilise a reliable method to identify SCD patients prior to transfusion, such as a required question/answer field on type/screen or crossmatch orders.

Conclusion

Many healthcare systems' transfusion practices for haemoglobinopathy patients are discordant with NHLBI/TIF recommendations. Efforts are needed to increase awareness and implementation of current recommendations among all transfusion services seeing these patients.

Losartan therapy decreases albuminuria with stable glomerular filtration and permselectivity in sickle cell anemia

Sickle cell nephropathy begins with hyperfiltration and microalbuminuria and may progress to renal failure. The aim of this study was to determine the effects of losartan on glomerular function and albumin excretion in sickle cell anemia (SCA). Individuals with SCA on hydroxyurea with persistent albuminuria were enrolled in a 1-year study of losartan. Glomerular filtration rate (GFR) measured by iohexol clearance, albumin excretion rate (AER), and fractional clearance of dextran were assessed at baseline, short-term (1-2month), and long-term (≥12month) intervals. Twelve subjects (6 microalbuminuria, 6 macroalbuminuria) completed short-term studies; 8 completed long-term studies. Baseline GFR was 112ml/min/1.73m² (71-147ml/min/1.73m²). AER decreased significantly at the short-term (median decrease -134 mcg/min, p=0.0063). GFR was not significantly-different at short-term or long-term intervals. Dextran clearance improved for diameters smaller than albumin (<36Å) but not larger sizes. Losartan therapy for ≥1year in sickle nephropathy results in lower albumin excretion with stable GFR. Filtration of neutral molecules ≥36Å was not changed by losartan, suggesting that the effect of losartan is a mechanism other than alteration of glomerular filtration size-selectivity.

Defining Sickle Cell Disease Mortality Using a Population-Based Surveillance System, 2004 through 2008

OBJECTIVE

Population-based surveillance data from California and Georgia for years 2004 through 2008 were linked to state death record files to determine the all-cause death rate among 12,143 patients identified with sickle cell disease (SCD).

METHODS

All-cause death rates, by age, among these SCD patients were compared with all-cause death rates among both African Americans and the total population in the two states. All-cause death rates were also compared with death rates for SCD derived from publicly available death records: the compressed mortality files and multiple cause of death files.

RESULTS

Of 12,143 patients identified with SCD, 615 patients died. The all-cause mortality rate for the SCD population was lower than the all-cause mortality rate among African Americans and similar to the total population all-cause mortality rates from birth through age 4 years, but the rate was higher among those with SCD than both the African American and total population rates from ages 5 through 74 years. The count of deceased patients identified by using population-based surveillance data (n=615) was more than twice as high as the count identified in compressed mortality files using SCD as the underlying cause of death alone (n=297).

CONCLUSION

Accurate assessment of all-cause mortality and age at death requires long-term surveillance via population-based registries of patients with accurately diagnosed SCD.

Newborn screening for sickle cell diseases in the United States: A review of data spanning 2 decades

Sickle cell disease is a group of disorders, the majority of which are detected through state newborn screening programs. There is limited knowledge of disease prevalence in the U.S.

POPULATION

We report 20 years of case finding and laboratory data for sickle cell disease and trait to assist in: planning for health services delivery; providing data for researchers; aiding in tracking health outcome trends; and assessing sickle gene prevalence in the newborn population. During the 20-year period, there were 39,422 confirmed cases of sickle cell disease among 76,527,627 newborn births screened (1:1941) and 1,107,875 laboratory reports of probable sickle trait among 73,951,175 newborn births screened (1:67). The highest sickle cell disease incidence during the 20 years was in the District of Columbia (1:437) followed by Mississippi (1:683) and South Carolina (1:771). For sickle cell trait, the highest incidences were in the District of Columbia (1:22), Mississippi (1:26), and South Carolina (1:31).

Factors associated with survival in a contemporary adult sickle cell disease cohort

In this study, the relationship of clinical differences among patients with sickle cell disease (SCD) was examined to understand the major contributors to early mortality in a contemporary cohort. Survival data were obtained for 542 adult subjects who were enrolled since 2002 at three university hospitals in the southeast United States. Subjects were followed up for a median of 9.3 years. At enrollment, clinical parameters were collected, including hemoglobin (Hb) genotype, baseline laboratory values, comorbidities, and medication usage. Levels of soluble adhesion molecules were measured for a subset of 87 subjects. The relationship of clinical characteristics to survival was determined using regression analysis. Median age at enrollment was 32 years. Median survival was 61 years for all subjects. Median survival for Hb SS and Sβ(0) was 58 years and for Hb SC and Sβ(+) was 66 years. Elevated white blood count, lower estimated glomerular filtration rate, proteinuria, frequency of pain crises, pulmonary hypertension, cerebrovascular events, seizures, stroke, sVCAM-1, and short-acting narcotics use were significantly associated with decreased survival. Forty-two percent of subjects were on hydroxyurea therapy, which was not associated with survival. SCD continues to reduce life expectancy for affected individuals, particularly those with Hb Sβ(0) and SS. Not only were comorbidities individually associated with decreased survival but also an additive effect was observed, thus, those with a greater number of negative endpoints had worse survival (P < 0.0001). The association of higher sVCAM-1 levels with decreased survival suggests that targeted therapies to reduce endothelial damage and inflammation may also be beneficial.

IMPROVE trial: a randomized controlled trial of patient-controlled analgesia for sickle cell painful episodes: rationale, design challenges, initial experience, and recommendations for future studies

BACKGROUND

The hallmark of sickle cell disease (SCD) is pain from a vaso-occlusive crisis. Although ambulatory pain accounts for most days in pain, pain is also the most common cause of hospitalization and is typically treated with parenteral opioids. The evidence base is lacking for most analgesic practice in SCD, particularly for the optimal opioid dosing for patient-controlled analgesia (PCA), in part because of the challenges of the trial design and conduct for this rare disease.

PURPOSE

The purpose of this report is to describe our Network's experiences with protocol development, implementation, and analysis, including overall study design, the value of pain assessments rather than 'crisis' resolution as trial endpoints, and alternative statistical analysis strategies.

METHODS

The Improving Pain Management and Outcomes with Various Strategies (IMPROVE) PCA trial was a multisite inpatient randomized controlled trial comparing two PCA-dosing strategies in adults and children with SCD and acute pain conducted by the SCD Clinical Research Network. The specified primary endpoint was a 25-mm change in a daily average pain intensity using a Visual Analogue Scale, and a number of related pain intensity and pain interference measures were selected as secondary efficacy outcomes. A time-to-event analysis strategy was planned for the primary endpoint.

RESULTS

Of 1116 individuals admitted for pain at 31 participating sites over a 6-month period, 38 were randomized and 4 withdrawn. The trial was closed early due to poor accrual, reflecting a substantial number of challenges encountered during trial implementation.

LIMITATIONS

While some of the design issues were unique to SCD or analgesic studies, many of the trial implementation challenges reflected the increasing complexity of conducting clinical trials in the inpatient setting with multiple care providers and evolving electronic medical record systems, particularly in the context of large urban academic medical centers.

LESSONS LEARNED

Complicated clinical organization of many sites likely slowed study initiation. More extensive involvement of research staff and site principal investigator in the clinical care operations improved site performance. During the subsequent data analysis, alternative statistical approaches were considered, the results of which should inform future efficacy assessments and increase future trial recruitment success by allowing substantial reductions in target sample size.

CONCLUSIONS

A complex randomized analgesic trial was initiated within a multisite disease network seeking to provide an evidence base for clinical care. A number of design considerations were shown to be feasible in this setting, and several pain intensity and pain interference measures were shown to be sensitive to time- and treatment-related improvements. While the premature closure and small sample size precluded definitive conclusions regarding treatment efficacy, this trial furnishes a template for design and implementation considerations that should improve future SCD analgesic trials.

High dose vitamin D therapy for chronic pain in children and adolescents with sickle cell disease: results of a randomized double blind pilot study

We report results of a pilot study of high-dose vitamin D in sickle cell disease (SCD). Subjects were given a 6-week course of oral high-dose cholecalciferol (4000-100 000 IU per week) or placebo and monitored prospectively for a period of six months. Vitamin D insufficiency and deficiency was present at baseline in 82·5% and 52·5% of subjects, respectively. Subjects who received high-dose vitamin D achieved higher serum 25-hydroxyvitamin D, experienced fewer pain days per week, and had higher physical activity quality-of-life scores. These findings suggest a potential benefit of vitamin D in reducing the number of pain days in SCD. Larger prospective studies with longer duration are needed to confirm these effects.

Chronic kidney disease and albuminuria in children with sickle cell disease

BACKGROUND AND OBJECTIVES

Sickle cell nephropathy begins in childhood and may progress to renal failure. Albuminuria is a sensitive marker of glomerular damage that may indicate early chronic kidney disease (CKD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The aims of this study were to determine the cross-sectional prevalence and clinical correlates of albuminuria and CKD among children with sickle cell disease (SCD). Over a 10-year period (1995 to 2005) 410 pediatric SCD patients ages 2 to 21 years were enrolled: 261 with hemoglobin SS (HbSS) or HbSβ(0) thalassemia (HbSβ(0)) and 149 with HbSC or HbSβ(+) thalassemia (HbSβ(+)). The albumin/creatinine ratio (ACR) of spot-urine specimens and serum creatinine were measured; abnormal albuminuria was defined as urinary ACR ≥ 30 mg/g.

RESULTS

The prevalence of abnormal albuminuria was 20.7% (23.0% in HbSS/HbSβ(0), 16.8% in HbSC/HbSβ(+)). Among HbSS/HbSβ(0), abnormal albuminuria was associated with increasing age and lower baseline hemoglobin. GFR, estimated in 189 patients using the updated Schwartz formula, correlated negatively with age (r = -0.27, P = 0.0002). CKD defined according to the Kidney Disease: Improving Global Outcomes study was present in 26.5% (50 of 189) of patients: stage 1 in 27 (14.8%) and stage 2 in 22 (11.6%). In multivariate analysis, age and HbSC/HbSβ(+) genotype were associated with CKD.

CONCLUSIONS

This is the first study to stage CKD in children with SCD and highlights a high prevalence of albuminuria and glomerular injury early in life. Detecting CKD in childhood could allow for earlier intervention and prevention of renal failure in adulthood.

MYH9 and APOL1 are both associated with sickle cell disease nephropathy

Renal failure occurs in 5-18% of sickle cell disease (SCD) patients and is associated with early mortality. At-risk SCD patients cannot be identified prior to the appearance of proteinuria and the pathobiology is not well understood. The myosin, heavy chain 9, non-muscle (MYH9) and apolipoprotein L1 (APOL1) genes have been associated with risk for focal segmental glomerulosclerosis and end-stage renal disease in African Americans. We genotyped 26 single nucleotide polymorphisms (SNPs) in MYH9 and 2 SNPs in APOL1 (representing the G1 and G2 tags) in 521 unrelated adult (18-83 years) SCD patients screened for proteinuria. Using logistic regression, SNPs were evaluated for association with proteinuria. Seven SNPs in MYH9 and one in APOL1 remained significantly associated with proteinuria after multiple testing correction (P < 0·0025). An MYH9 risk haplotype (P = 0·001) and the APOL1 G1/G2 recessive model (P < 0·0001) were strongly associated with proteinuria, even when accounting for the other. Glomerular filtration rate was negatively correlated with proteinuria (P < 0·0001), and was significantly predicted by an interaction between MYH9 and APOL1 in age-adjusted analyses. Our data provide insight into the pathobiology of renal dysfunction in SCD, suggesting that MYH9 and APOL1 are both associated with risk.

Beneficial effects of nitric oxide breathing in adult patients with sickle cell crisis

Pain from vaso-occlusive crisis (VOC) is the major cause of hospitalization in patients with sickle cell disease (SCD). The beneficial therapeutic effects of inhaled nitric oxide (NO) on the pathophysiology of SCD have been reported. A double-blind, randomized, placebo-controlled clinical trial was conducted to determine whether NO breathing reduces acute VOC pain in adult patients and to study the safety of inhaled NO. Twenty-three patients experiencing acute VOC were enrolled. After randomization but before treatment, five were found to not meet final eligibility criteria. Nine patients were assigned to inhaled NO (80 ppm) and nine to placebo (21% O2). Primary outcome was the mean change in pain scores after 4 hr of inhalation, measured on a 10-cm visual analog scale (VAS). Both groups had similar baseline VAS pain scores but inhaled NO significantly reduced pain scores compared with placebo (P 5 0.02) at the end of NO inhalation. Secondary outcome was parenteral morphine use at baseline, 4, and 6 hr. Parenteral morphine use was lower in the inhaled NO group, but the difference was not statistically significant.Safety assessments included systolic blood pressure measurements,pulse oximetry readings, concentration of delivered nitrogen dioxide, and concentration of methemoglobin (metHb). None of these NO toxicities was observed.

Surgical and obstetric outcomes in adults with sickle cell disease

BACKGROUND

Sickle cell disease patients are more likely than the general population to undergo surgery and usually do so at a younger age. Female sickle cell disease patients also have special gynecological and obstetric issues related to their disease.

METHODS

We collected data through standardized clinical report forms, patient interviews, and medical records from 509 adult sickle cell disease patients. Logistic regression was used to estimate the association between multiple variables and each of the surgery types. We also determined the prevalence and outcomes of pregnancy in 284 women with sickle cell disease in this population.

RESULTS

Almost 50% of patients aged 18-27 years had had a cholecystectomy. Mean corpuscular hemoglobin, total bilirubin, and lactate dehydrogenase were significantly higher in the postcholecystectomy group; 9.5% of 504 individuals had undergone splenectomy. Hematocrit, body mass index, and red blood cell count were significantly higher in the postsplenectomy group. Hip replacement had been performed in 9.2% of individuals, with the prevalence increasing as early as the fourth decade and continuing to increase through the sixth decade of life. A history of pregnancy was present in 190 women (67%). Of 410 pregnancies, only 53.9% resulted in live births, 16.6% were voluntarily terminated, and 29.5% were complicated by miscarriage, still birth, or ectopic implantation.

CONCLUSIONS

Sickle cell disease continues to have a strong effect on the mean age for common surgeries and impacts pregnancy outcomes. We conclude that this population has a unique surgical and obstetric history that should be further studied to provide insight into potentially more effective preventive approaches to end-organ damage.

Compound heterozygosity for hemoglobin C and hemoglobin Korle-Bu

We describe a case of compound heterozygosity for hemoglobin C (beta6 Glu-->Lys) and hemoglobin Korle-Bu (beta73 Asp-->Asn). To our knowledge, this is the third case report of this unusual hemoglobin genotype, and the first to integrate data from cation exchange high-performance liquid chromatography, hemoglobin electrophoresis, and beta-globin gene sequencing. The principal hematological finding in our case was microcytosis without significant anemia. The previous case reports of this hemoglobinopathy also describe microcytosis, with varying degrees of hemolytic anemia. Given the relative gene frequencies of hemoglobins C and Korle-Bu, the occurrence of this compound-heterozygous genotype should be anticipated in people of African ancestry.

Genetic polymorphisms associated with priapism in sickle cell disease

Priapism occurs in 30-45% of male patients with sickle cell disease (SCD), but the possible influence of genetic risk factors on the incidence of priapism is not well understood. We examined genetic polymorphisms in 199 unrelated, adult (>18 years), male patients with Hb SS and Hb Sbeta(0)-thalassaemia, 83 (42%) of whom reported a history of priapism. Candidate genes for association with priapism were identified based on their involvement in adhesion, coagulation, inflammation and cell signalling. Additionally, we examined genes involved in nitric oxide biology (NOS2, NOS3, SLC4A1), as well as polymorphisms in the klotho (KL) gene, which has previously been associated with priapism. Strong evidence of association was found for single nucleotide polymorphisms in transforming growth factor-beta receptor, type III (TGFBR3) (rs7526590; P = 0.00058), aquaporin (AQP1) (rs10244884; P = 0.00068), integrin alphav (ITGAV) (rs3768780; P = 0.00090), and the A1 subunit of coagulation factor XIII (F13A1) (hcv1860621; P = 0.00156). Associations with TGFBR3, AQP1, and ITGAV remained significant after adjusting for multiple testing, using the Benjamini-Hochberg procedure. Our data suggest that genes involved in the TGFbeta pathway, coagulation, cell adhesion and cell hydration pathways may be important in risk for priapism.

Blood Is Thicker Than Water

Complications of chronic hypoxia, including erythrocytosis, hyperviscosity, abnormalities of hemostasis, cerebral abscesses, stroke, and endocarditis, are among the most common consequences of cyanotic heart disease in adults. The compensatory erythrocytosis of cyanotic heart disease can become pathologic by causing an increase in blood viscosity, thereby decreasing perfusion and resulting in decreased total oxygen delivery and increased risk of venoocclusive/hyperviscosity syndrome. Treatment of hyperviscosity secondary to erythrocytosis in cyanotic heart disease is controversial. Data is limited but suggest that phlebotomy has the potential to increase exercise capacity, reduce the symptoms of hyperviscosity, and reduce the potential risk of vasoocclusive disease in selected patients with polycythemia secondary to cyanotic heart disease. Unfortunately, repeated phlebotomy can quickly lead to iron deficiency, resulting in microcytic erythrocytes that induce higher viscosity than normocytic erythrocytes, which may increase the risk for venoocclusive events. There are limited data on the use of hydroxyurea to suppress erythrocytosis in this patient population. The authors conclude that until newer approaches to decreasing hematocrit without inducing iron deficiency are shown to be safe and efficacious, phlebotomy should only be used for the acute resolution of hyperviscosity symptoms. In addition, the use of hydroxyurea should be limited to patients with recurrent symptoms.

Hydroxyurea and sickle cell anemia: effect on quality of life

Background

The Multicenter Study of Hydroxyurea (HU) in Sickle Cell Anemia (MSH) previously showed that daily oral HU reduces painful sickle cell (SS) crises by 50% in patients with moderate to severe disease. The morbidity associated with this disease is known to have serious negative impact on the overall quality of life(QOL) of affected individuals.

Methods

The data in this report were collected from the 299 patients enrolled in the MSH. Health quality of llife (HQOL) measures were assessed in the MSH as a secondary endpoint to determine if the clinical benefit of HU could translate into a measurable benefit perceptible to the patients. HQOL was assessed with the Profile of Mood States, the Health Status Short Form 36 (SF-36), including 4-week pain recall, and the Ladder of Life, self-administered twice 2-weeks apart pre-treatment and every 6 months during the two-year, randomized, double-blind, treatment phase. The effects of factors including randomized treatment, age, gender, pre-treatment crises frequency, Hb-F level mean, daily pain from 4-week pre-treatment diaries, and 2-year Hb-F response level (low or high) were investigated.

Results

Over two years of treatment, the benefit of HU treatment on QOL, other than pain scales, was limited to those patients taking HU who maintained a high HbF response, compared to those with low HbF response or on placebo. These restricted benefits occurred in social function, pain recall and general health perception. Stratification according to average daily pain prior to treatment showed that responders to HU whose average daily pain score was 5–9 (substantial pain) achieved significant reduction in the tension scale compared to the placebo group and to non-responders. HU had no apparent effect on other QOL measures.

Conclusion

Treatment of SS with HU improves some aspects of QOL in adult patients who already suffer from moderate-to-severe SS.

Histamine increases sickle erythrocyte adherence to endothelium

Complications of sickle cell anaemia include vascular occlusion triggered by the adherence of sickle erythrocytes to endothelium in the postcapillary venules. Adherence can be promoted by inflammatory mediators that induce endothelial cell adhesion molecule expression and arrest flowing erythrocytes. The present study characterised the effect of histamine stimulation on the kinetics of sickle cell adherence to large vessel and microvascular endothelium under physiological flow. Increased sickle cell adherence was observed within minutes of endothelial activation by histamine and reached a maximum value within 30 min. At steady state, sickle cell adherence to histamine-stimulated endothelium was 47 +/- 4 adherent cells/mm(2), 2.6-fold higher than sickle cell adherence to unstimulated endothelial cells. Histamine-induced sickle cell adherence occurred rapidly and transiently. Studies using histamine receptor agonists and antagonists suggest that histamine-induced sickle cell adhesion depends on simultaneous stimulation of the H(2) and H(4) histamine receptors and endothelial P-selectin expression. These data show that histamine release may promote sickle cell adherence and vaso-occlusion. In vivo histamine release should be studied to determine its role in sickle complications and whether blocking of specific histamine receptors may prevent clinical complications or adverse effects from histamine release stimulated by opiate analgesic treatment.

Sickle cell adhesion depends on hemodynamics and endothelial activation

Venular microvascular circulation in patients with sickle cell anemia exhibits reduced and episodic blood flow. Sickle erythrocyte adhesion to postcapillary venule endothelium is postulated to initiate and propagate episodes of vasoocclusive pain. Hemodynamics likely mediate the adherence of sickle cells to endothelium, controlling delivery of potentially adherent erythrocytes and removal of loosely adherent erythrocytes on the endothelium. This study found a high dependence on shear stress of sickle erythrocyte adhesion to vascular cell adhesion molecule-1 (VCAM-1) on endothelium stimulated by tumor necrosis factor-alpha (TNF-alpha). Shear stress varied from 1.0 dyne/cm 2 (microvascular venular flow), in which VCAM-1 ligand interactions induced by TNF-alpha primarily controlled adherence, to 0.1 dyne/cm 2 (low flow), in which stimulation had little effect on adherence. At shear stresses analogous to in vivo velocities from laser Doppler ultrasound studies (0.8 and 0.6 dyne/cm 2 ), TNF-alpha promoted 1.9- and 2.7-fold increases in adhesion compared with unstimulated (baseline) adherence. These findings suggest a dynamic vasoocclusive process that depends on both receptor expression and shear stress. These results indicate that, in the microvasculature, slightly reduced inflow rate, increased receptor expression, or both may result in large increases in sickle erythrocyte adhesion.

Enhanced pulmonary and systemic response to endotoxin in transgenic sickle mice

Some suggest that sickle cell disease (SCD) is associated with a "proinflammatory state" that predisposes patients to acute chest syndrome in the setting of triggering factors. Conflicting data emerged when inflammation markers in SCD were compared with healthy individuals. Therefore, we examined transgenic sickle and control mice at baseline and with endotoxin (LPS) intraperitoneal injection to determine whether a proinflammatory state truly exists. At baseline, sickle mice had elevated levels of circulating leukocytes and soluble vascular cell adhesion molecule 1 (sVCAM-1). No other differences were observed at baseline or in response to saline. However, LPS challenge was associated with significant increases in mortality (p<0.05), airway tone (p<0.03), serum and bronchoalveolar lavage levels of cytokines tumor necrosis factor-alpha (p<0.03), interleukin-1beta (p<0.02), and sVCAM-1 (p<0.01) in sickle mice compared with control subjects. Furthermore, 4 hours after LPS, microarray analysis identified 413 genes differentially expressed in the sickle mice (n=5) compared with only 7 in the control subjects (n=5). No difference in lung parenchyma was observed by light microscopy. This enhanced response to LPS suggests that the sickle red blood cell confers a subclinical "proinflammatory state." This enhanced response to inflammatory insult, particularly by adhesion molecules such as sVCAM-1, could play a role in the increased susceptibility to pulmonary dysfunction that has been observed clinically in SCD.

Invasive pneumococcal infections in children with sickle cell disease in the era of penicillin prophylaxis, antibiotic resistance, and 23-valent pneumococcal polysaccharide vaccination

Rates and severity of pneumococcal infections in children with sickle cell disease were examined before licensure of pneumococcal-conjugated vaccine (PVC). Rates of peak invasive infection rates in 1-year-old children with hemoglobin SS and mortality in those 0 to 10 years of age were 36.5 to 63.4 and 1.4 to 2.8 per 1000 person-years, respectively (>10 and 100 times as frequent as in the general population). Overall, 71% of serotyped isolates (n=80) were PVC serotypes and 71% of nonvaccine serotype strains were penicillin-sensitive. Clinical presentation in children with hemoglobin SS (n=71; more with hypotension) and hemoglobin SC (n=18; more with acute chest syndrome, otitis media) differed. Penicillin nonsusceptibility (38% of isolates) varied between geographic study sites. Penicillin prophylaxis appeared less effective against intermediate and resistant strains. Of all infected children, meningitis developed in 20% and 15% died (hemoglobin SS, n=15 and 11; hemoglobin SC, n=1 each). Factors associated with death included age >4 years (58%), serotype 19F, and not being followed by a hematologist (42% each). The pneumococcal-polysaccharide vaccine was 80.4% effective within 3 years after vaccination (95% CI, 39.7, 93.6). Children with sickle cell disease of all ages may benefit from PVC boosted with polysaccharide vaccination.

Inflammatory mediators promote strong sickle cell adherence to endothelium under venular flow conditions

Adherence of sickle erythrocytes to endothelium in venules is thought to initiate or propagate vaso-occlusive episodes. Because of blood shear forces with normal microvascular flow, adherence in post-capillary venules requires binding via high-affinity receptor-mediated pathways. Microvascular flow in sickle patients is episodic, even in asymptomatic patients, so adherence may also occur at low shear not requiring high-affinity binding. Sickle cell binding to endothelium was quantified under flow or static incubation with unusually large vWF, thrombospondin, alpha(4)beta(1)/VCAM-1 or alpha(4)beta(1)/fibronectin (FN). Adherence under flow at 0.5 dyne/cm(2) shear stress leads to the greatest number of adherent sickle cells. Adherence under flow at 1.0 dyne/cm(2) leads to the strongest adherence. Static incubation conditions promote weak adherence of low numbers of sickle cells to endothelium. Following attachment at 1.0 dyne/cm(2), adherence strength was 2.5 +/- 0.1 or 2.6 +/- 0.2 dynes/cm(2) for alpha(4)beta(1)/VCAM-1 or alpha(4)beta(1)/FN pathways, a level 50% greater than adherence strength mediated by thrombospondin or ULvWF (1.7 +/- 0.08 or 1.6 +/- 0.07 dynes/cm(2), respectively). Sickle cell adhesion promoted by simultaneous activation of alpha(4)beta(1)/VCAM-1 and alpha(4)beta(1)/FN pathways is the strongest at 6.2 +/- 0.2 dynes/cm(2) and adherent red cells resist detachment shear stresses up to 10 dynes/cm(2). These data demonstrate that sickle cell adhesion to endothelium is regulated both by receptor/ligand affinity and flow conditions. Thus, both microvascular flow conditions and receptor-ligand interactions may regulate sickle cell adherence in vivo.

Sickle erythrocyte adherence to endothelium at low shear: role of shear stress in propagation of vaso-occlusion

Under venular flow conditions, sickle cell adherence to endothelium is mediated by cell adhesion molecules and adhesive proteins associated with inflammation, coagulation, and endothelial perturbation. Periodic and reduced blood flow are observed in sickle microcirculation during hematologic steady state, suggesting that blood flow is compromised in sickle microcirculation. We tested the hypothesis that low blood flow enhances adherence by quantifying sickle cell adhesion to endothelium under venular flow (1.0 dyne/cm(2) shear stress) and low flow (0.1 dyne/cm(2) shear stress), with and without addition of adhesion promoting agonists. Under low flow, sickle cell adherence to endothelium increases with contact time in the absence of endothelial activation or adhesive protein addition. In contrast, at venular shear stress, sickle cell adherence only occurs following endothelial activation with TNF-alpha or addition of thrombospondin. Analysis of these data with a mathematical model reveals that at low flow adherence is "transport-controlled," meaning that contact time between sickle cells and endothelium is a more important determinant of adherence than high-affinity receptor-ligand interactions. Low-affinity interactions are sufficient for adhesion at low flow. In contrast, at venular flow (1 dyne/cm(2) shear stress) adherence is "affinity-controlled," meaning that adherence requires induction of specific high-affinity receptor-ligand interactions. These findings demonstrate that in addition to activating factors and adherence proteins, microvascular shear stress is an important determinant of sickle cell adhesion to endothelium. This suggests that in vivo, erythrostasis is an important determinant of adhesion that can act either independently or concurrently with ongoing acute events to induce adhesive interactions and vaso-occlusion.

Reduction of pain episodes and prothrombotic activity in sickle cell disease by dietary n-3 fatty acids

The effects of dietary n-3 fatty acids (n-3FAs) on the frequency of pain episodes and ex vivo blood tests of thrombosis have been evaluated in patients with sickle cell disease (SCD) utilizing a double-blind, olive oil-controlled clinical trial. Dietary n-3FA therapy (0.1 g/kg/d) was provided as menhaden fish oil (0.25 g/kg/d) containing 12% eicosapentaenoic acid (EPA), and 18% docosahexaenoic acid (DHA). Within 1 month dietary n-3FAs exchanged with n-6FAs in plasma and erythrocyte membrane phospholipids (p <0.01 in all cases). Treatment with dietary n-3FAs for 1 year reduced the frequency of pain episodes requiring presentation to the hospital from 7.8 events during the preceding year to 3.8 events/year (p <0.01; n = 5). By contrast, subjects receiving control dietary olive oil (n = 5) experienced 7.1 pain events/year, compared to 7.6 during the previous year (p >0.4). The reduction in episodes in n-3FA-treated subjects was also significant when compared to control subjects (p <0.01). Dietary n-3FA therapy was not associated with hemorrhagic, gastrointestinal or other adverse effects. Compared to 10 asymptomatic African-American controls, sickle cell subjects demonstrated significantly increased pretreatment: 1) flow cytometric expression of platelet membrane P-selectin (CD62p; p <0.01) and annexin V binding sites (p = 0.02); 2) plasma levels of platelet-specific secretory proteins platelet factor 4 (PF4) and beta-thromboglobulin (betaTG) (p <0.01 in both cases); 3) plasma products of thrombin generation, prothrombin fragment 1.2 (F1.2) and thrombin:antithrombin (TAT) complex (p <0.01 in both cases); and 4) plasma levels of thrombolytic products, D-dimer and plasmin:antiplasmin (PAP) complex (p <0.01 in both cases). Treatment with dietary n-3FAs concurrently decreased plasma levels of F1.2, D-dimer, and PAP (p <0.05, compared to olive oil controls), implying that the reduction in pain events was related to n-3FA-dependent inhibition of thrombosis. We conclude that dietary n-3FAs reduce the frequency of pain episodes perhaps by reducing prothrombotic activity in sickle cell disease.

Thrombogenesis in sickle cell disease

Thirty-three subjects with sickle cell disease (SCD), 11 during episodes of pain and 22 during periods without pain, were evaluated for in vivo thrombogenic activities as compared with 10 normal black control subjects. Measurements were performed for (1) platelet surface activation, assessing flow cytometric expression of activated integrin alpha(IIb)beta(3) receptor (GPIIb/IIIa, CD41a) and P-selectin (CD62p); (2) platelet and erythrocyte surface procoagulant activities, measuring flow cytometric binding of activated factor (FVa) and annexin V; (3) plasma levels of platelet-specific secreted proteins platelet factor 4 (PF4) and beta-thromboglobulin (betaTG); (4) plasma markers of thrombin generation, prothrombin activation fragment (F(1.2)), and thrombin: antithrombin complex (TAT); and (5) plasma markers of fibrinolysis, D -dimer, and plasmin:antiplasmin complex (PAP). As compared with control subjects, asymptomatic subjects with SCD demonstrated significantly increased platelet activation (P <.01 for P-selectin and annexin V binding), elevated plasma levels of PF4 and betaTG (P <.01 and P <.03, respectively), and increased plasma concentrations of F(1.2), TAT, PAP, and D -dimer (P <.05 in all cases). During episodes of SCD pain, platelet activation was increased as compared with periods without pain (P <.01 for expression of activated integrin alpha(IIb)beta(3) receptor and P-selectin and binding of FVa and annexin V), erythrocytes expressed procoagulant activities (P <.01 for FVa and annexin V binding), and platelet microparticles appeared in the circulation (3% to 30%; P <.001). SCD pain episodes were associated with elevated plasma levels of F(1.2), TAT, PAP, and D -dimer (P <.05 as compared with asymptomatic intervals). The frequency of pain episodes correlated with enhanced platelet procoagulant activity (r = 0.61, P <.05) and elevated plasma fibrinolytic activity (r = 0.74, P <.01) measured during periods without pain. Plasma fibrinolytic activity was inversely correlated with time to the next pain episode (r = -0.50, P <.05). Thus, asymptomatic subjects with SCD exhibit ongoing platelet activation, thrombin generation, and fibrinolysis that increases during episodes of pain. These changes are predictive of frequency of pain and interval to next pain episode, thereby implicating thrombogenic activity in the development of SCD pain episodes.

Techniques for blood administration in sickle cell patients

Transfusion therapy provides many benefits to Individuals with sickle cell disease but may lead to cardiovascular complications, alloimmunization, exposure to infection, and iron overload. Simple transfusion is used to increase oxygen-carrying capacity. Chronic simple transfusion is useful in preventing a number of complications in sickle cell disease. Acute erthrocyte exchange transfusion can reduce the percentage of cells containing sickle hemoglobin while decreasing volume overload and minimizing hyperviscosity. Chronic erythrocyte exchange transfusion reduces iron loading but Increases donor exposure. Directed odnation may reduce alloimmunization and exposure to infection.

Activation of vascular endothelial cell adhesion molecule expression by sickle blood cells

Microvascular complications in sickle cell disease occur as a result of obstruction of small vessels by deoxygenated sickle cells. Cerebrovascular complications are also common and result from obstruction of large blood vessels by thrombosis with changes in vessels that have some similarity to those found in arteriosclerotic vascular disease. Endothelial damage and activation from sickle cell-endothelial interactions may contribute to both. We find that endothelial cells have increased expression of VCAM-1, E-selectin, and ICAM-1 when exposed to sickle blood cells. The concentration-dependent, sickle-induced, adhesion molecule expression is significantly greater than that promoted by normal cells. The time course of Cell Adhesion Molecule (CAM) expression is similar to that induced by TNF-alpha and IL1. Studies after white cell enrichment and reduction suggest leukocytes are the primary mediators. CAM expression by endothelial cells appears stimulated by soluble factors. Antibody inhibition studies support TNF-alpha and IL-1, produced by sickle leukocytes, as the primary soluble factors responsible for the observed CAM expression. Both the induction of endothelial CAM expression and subsequent endothelial adherence of sickle erythrocytes may play significant roles in the pathophysiology of sickle-related complications, and reduction in CAM expression may provide a new approach to treatment.

Evidence that microdeletions in the alpha globin gene protect against the development of sickle cell glomerulopathy in humans

There is a large variability in the severity of the clinical manifestations of sickle cell anemia (SSA), including renal involvement. Haplotypes in the beta-globin gene cluster associated with the geographical origin of the sickle mutation, as well as microdeletions in the alpha-globin genes, could provide an epigenetic influence on the heterogeneous outcome in SSA. It has been determined that the cause of progressive renal insufficiency in SSA is a glomerulopathy, clinically detected by the presence of macroalbuminuria (albumin excretion rate >300 mg/g creatinine). To investigate the role of the alpha-globin gene microdeletion and beta-globin gene cluster haplotypes on the degree of glomerular involvement, 76 adult SSA patients (hemoglobin SS) were studied to determine the relationship between these genetic markers and the development of sickle cell glomerulopathy. Macroalbuminuria was present in 22 (29%) of 76 adult SSA patients. The coinheritance of microdeletions in one or two of the four alpha-globin genes (alpha-thalassemia) was associated with a lower prevalence of macroalbuminuria (13%) versus patients with intact alpha-globin genes (40%, P = 0.01). By contrast, there was no association between albuminuria and beta-globin gene haplotypes (Central African Republic [CAR] versus non-CAR haplotypes). Patients with alpha-globin gene microdeletions had lower mean corpuscular volumes and mean corpuscular hemoglobin concentration than patients with all four alpha genes (86+/-2 versus 99+/-3 fl, and 33.9+/-0.2 versus 34.9+/-0.2%, respectively, P<0.05). There were no such hematologic differences between CAR and non-CAR beta-globin haplotypes. There were no differences in duration of disease (age), hemoglobin levels, reticulocyte index, and lactate dehydrogenase levels between those with and without glomerulopathy, but the mean arterial pressure was higher (87+/-1 mm Hg) in patients with intact alpha gene locus versus those with microdeletions (80+/-2 mm Hg, P<0.05). It is concluded that the coinheritance of microdeletions in the alpha-globin gene locus in SSA patients confers "renoprotection" by mechanisms not related to the degree of anemia or the severity of hemolysis, but could be related to a reduced mean corpuscular volume or to a lower erythrocyte hemoglobin concentration.

Family functioning and social support in the adaptation of caregivers of children with sickle cell syndromes

OBJECTIVE

To examine moderating effects of family functioning and social support on the relationship of child-related stressors to caregivers' psychological adaptation in a sample of caregivers of children with a chronic illness.

METHOD

Participants were 67 caregivers of children and adolescents with sickle cell syndromes. We conducted MANOVAs and subsequent effect size calculations to determine if family functioning would buffer the effects of caring for difficult-to-manage children with this illness.

RESULTS

Findings supported a moderator effect of family functioning on the association of children's externalizing behavioral problems to caregivers' symptoms of hostility. Greater levels of cohesive and adaptive family functioning buffered the potential detrimental effects of caring for children perceived as hard to manage. No significant associations were obtained between measures of caregivers' psychological adaptation and the severity of their children's disease.

CONCLUSIONS

We make recommendations for family systems interventions, particularly for caregivers of children with behavior problems.

Leg ulcers in sickle cell disease

Leg ulcers are a frequent complication in patients with sickle cell anemia and S/beta thalassemia causing significant physical disability and negative psychologic and social impact. Systematic conservative approaches to treatment using gentle debridement and control of edema result in rapid healing of most ulcers. Chronic recalcitrant ulcers are a challenge to the clinician and patient. Controlled clinical trials are not available to fully define the therapeutic approach to the chronic leg ulcers.

Inhibition of plasma-mediated adherence of sickle erythrocytes to microvascular endothelium by conformationally constrained RGD-containing peptides

Adherence of sickle erythrocytes to vascular endothelium likely initiates or participates in microvascular occlusion, leading to ischemic tissue and organ damage characteristic of sickle-cell pain episodes. In vitro, sickle-cell adherence to endothelium involves adhesive plasma proteins and integrin and nonintegrin receptors on sickle cells and endothelial cells. The involvement of arginine-glycine-aspartic acid (RGD) sequences in adhesive plasma proteins and integrin receptors suggests that RGD-containing peptides may inhibit sickle-cell/endothelial-cell adherence. In the present study, inhibition of plasma-mediated sickle-erythrocyte adherence to endothelium using conformationally constrained RGD-containing peptides was quantified in vitro under continuous flow at a shear stress of 1.0 dyn/cm2. Two conformationally constrained RGD peptides were investigated: 6Z (which has high affinity for alpha5beta1, alpha(V)beta3, and alpha(IIIb)beta3 integrin receptors), and TP9201 (which preferentially binds to alpha(IIb)beta3). Peptide 6Z at 50 microM inhibited plasma-mediated sickle-cell adherence to microvascular endothelium 70% when incubated with sickle red cells, and 63% when incubated with endothelium. Under similar conditions, peptide TP9201 inhibited plasma-mediated sickle-cell adherence up to 85% at concentrations from 250 to 500 microM TP9201. The inhibition of plasma-mediated adherence by conformationally constrained RGD peptides, but not by linear or circular constructs, suggests that the tertiary structure of the peptide containing the binding sequence is important. Inhibition of plasma-mediated sickle-cell adhesion with these peptides in vitro suggests that such conformationally constrained RGD peptides could provide therapeutic interventions in the course of the disease by inhibiting receptor-ligand interactions.

Bone marrow transplantation for sickle cell disease

BACKGROUND

We investigated the risks and benefits of allogeneic bone marrow transplantation in children with complications of sickle cell disease.

METHODS

Twenty-two children less than 16 years of age who had symptomatic sickle cell disease received marrow allografts from HLA-identical siblings between September 1991 and April 1995. The indications for transplantation included a history of stroke (n = 12), recurrent acute chest syndrome (n = 5), and recurrent painful crises (n = 5). Patients were prepared for transplantation with busulfan, cyclophosphamide, and antithymocyte globulin.

RESULTS

Twenty of the 22 patients survived, with a median follow-up of 23.9 months (range, 10.1 to 51.0), and 16 patients had stable engraftment of donor hematopoietic cells. In three patients the graft was rejected and sickle cell disease recurred; in a fourth patient graft rejection was accompanied by marrow aplasia. In 1 of the 16 patients with engraftment, there was stable mixed chimerism. Two patients died of central nervous system hemorrhage or graft-versus-host disease. Kaplan-Meier estimates of survival and event-free survival at four years were 91 percent and 73 percent, respectively. Among patients with a history of acute chest syndrome, lung function stabilized; among patients with prior central nervous system vasculopathy who had engraftment, stabilization of cerebrovascular disease was documented by magnetic resonance imaging.

CONCLUSIONS

Allogeneic stem-cell transplantation can be curative in young patients with symptomatic sickle cell disease.

Barriers to bone marrow transplantation for sickle cell anemia

While allogeneic marrow transplantation is curative therapy for patients with sickle cell anemia, only a small fraction of patients in the United States receive this treatment. We surveyed participants in our multicenter study of marrow transplantation for sickle cell anemia to determine reasons for not proceeding to transplantation. Among the 4848 patients less than 16 years of age with sickle cell anemia that were followed in 22 collaborating centers, 315 (6.5%) patients were reported to meet protocol entry criteria for transplantation, although there was wide variation among the institutions (0.9-36%). Among the 315 patients eligible for transplantation, 128 (41%) had human leukocyte antigen (HLA) typing performed, and of these 44 (14% of those meeting entry criteria) had an HLA-identical sibling. Common reasons for not proceeding with HLA typing in the remaining 187 patients included lack of a candidate sibling donor (76 patients, 24% of those meeting criteria) and lack of financial or psychosocial support (33, 10.5%). Parental refusal (30, 9.5%), physician refusal (13, 4%), history of medical noncompliance (2, < 1%), and other reasons (33, 10.5%) were less frequently cited. To date, 25 patients have been transplanted. Of the remaining 19 patients with HLA-matched donors, seven did not proceed to transplantation because of parental refusal, while the others anticipate a future transplantation (6), have experienced symptomatic improvement (4), or have relocated abroad (2). We conclude that the major barrier to marrow transplantation for sickle cell anemia is lack of an HLA-identical donor. But since only 6.5% of all children with sickle cell disease were considered eligible for transplantation, it is possible that other significant obstacles remain to be identified. For patients reported to meet eligibility criteria, parental refusal and limited financial or psychosocial support were infrequent barriers to transplantation.

Molecular basis of sickle cell-endothelial cell interactions

Adherence of sickle erythrocytes to microvascular endothelium is posited to initiate or contribute to sickle cell vaso-occlusive pain episodes. Adherence and occlusion in vivo may depend on hemodynamics interacting with plasma, erythrocyte, and endothelial cell factors. Four receptor-mediated adherence pathways have been described to date: adherence mediated by high molecular weight von Willebrand factor multimers bridging glycoprotein lb-like and integrin receptors on sickle cells and similar receptors on endothelial cells; thrombospondin bridging CD36 on sickle reticulocytes and the alpha v beta 3 integrin on large-vessel endothelial cells or alpha v beta 3 and CD36 on microvascular endothelium; binding of sickle reticulocyte alpha 4 beta 1 receptors to vascular cell adhesion molecule 1 expressed on endothelial cells stimulated by cytokine or double-stranded RNA viruses; and binding of sickle cells to endothelial cell-associated fibronectin via sickle reticulocyte alpha 4 beta 1 activated by phorbol ester or interleukin-8. The significance of these adherence pathways in sickle cell vaso-occlusion is discussed.

Practical guide to the diagnosis of thalassemia. Council of Regional Networks for Genetic Services (CORN)

Thalassemias occur in individuals of all ethnic backgrounds and are among the most common genetic diseases worldwide. The diagnosis of thalassemia can easily be part of primary medical practice. Here we outline a practical approach to the detection of thalassemias in three common clinical settings. The first involves any patient with a low mean corpuscular volume (MCV) with or without anemia. The second is a neonatal screening result indicating possible presence of thalassemia. Finally, evaluation for thalassemia should be considered in the context of family planning or pregnancy in patients whose ethnicity indicates origin from high risk geographic areas. We also review the various types of the thalassemia syndromes and provide an overview of general therapeutic considerations.

Double-stranded RNA induces sickle erythrocyte adherence to endothelium: a potential role for viral infection in vaso-occlusive pain episodes in sickle cell anemia

Vaso-occlusive pain episodes in sickle cell anemia are hypothesized to be precipitated by adherence of sickle erythrocytes to vascular endothelium in the microcirculation. Febrile episodes, thought to be viral in etiology, are frequently associated with vaso-occlusion; however, a direct link between viral infection and vascular occlusion has not yet been established. Many pathogenic viruses contain double-stranded RNA or replicate through double-stranded RNA intermediates. Double-stranded RNA has been shown to induce vascular cell adhesion molecule-1 (VCAM-1) protein expression on endothelial cells. Recently, a new adhesion pathway has been described between VCAM-1 expressed on cytokine stimulated endothelium and the alpha 4 beta 1 integrin complex expressed on sickle reticulocytes. Based on these observations, the hypothesis was developed that viral infection, through double-stranded RNA intermediates, increases endothelial VCAM-1 expression leading to sickle erythrocyte adhesion to endothelium via an alpha 4 beta 1-VCAM-1--dependent mechanism. In support of this hypothesis, endothelial cells exposed to the synthetic double-stranded RNA poly(I:C) or the RNA virus parainfluenza 1 (Sendai virus) express increased levels of VCAM-1 and support increased sickle erythrocyte adherence under continuous flow at 1.0 dyne/cm2 shear stress as compared with unstimulated endothelium. Blocking antibodies directed against either VCAM-1 on the endothelium or alpha 4 beta 1 on sickle erythrocytes inhibit nearly all of the increased sickle cell adherence caused by poly(I:C) or Sendai virus. These results support the hypothesis that viruses, through double-stranded RNA elements, can induce sickle erythrocyte adherence to endothelium through alpha 4 beta 1-VCAM-1--mediated adhesion and provide a potential link between viral infection and microvascular occlusion precipitating sickle cell pain episodes.

Accelerated healing of chronic sickle-cell leg ulcers treated with RGD peptide matrix. RGD Study Group

Leg ulcers are a chronic manifestation of sickle-cell disease (SCD) and are often painful, disabling, and difficult to treat. RGD peptide matrix treatment is a novel therapy designed to provide a topical synthetic extracellular matrix that can act as a temporary substitute for the damaged natural matrix at the ulcer site. In this randomized, placebo-controlled, double-blind, prospective, multicenter investigation, SCD patients with full-thickness leg ulcers were treated with standard therapy plus RGD peptide matrix or saline placebo once weekly for up to 10 weeks. Healing in patients with chronic ulcers (2 months or greater in duration) was significantly accelerated (P = .0085) in RGD peptide matrix recipients compared with the placebo group. In these chronic ulcer cases, the average percent ulcer closure (decrease in ulcer surface area) in the RGD peptide matrix group (54.4% +/- 8.9%) exceeded that in the placebo group (19.0% +/- 24.3%) nearly threefold by study endpoint. Furthermore, RGD peptide matrix was equally effective in promoting healing of long persistent ulcers and ulcers of shorter duration. In contrast, standard therapy plus placebo was significantly less effective (P = .001) in promoting healing for ulcers of progressively greater duration. The results of this study provide preliminary evidence that RGD peptide matrix treatment may significantly accelerate healing of chronic sickle-cell leg ulcers.

Comparison of liquid and dried blood for neonatal hemoglobinopathy screening: laboratory and programmatic issues

OBJECTIVES

To compare laboratory and programmatic issues in neonatal hemoglobin screening in two systems using either liquid cord blood or heel puncture blood dried on filter paper (DB) to determine the accuracy of hemoglobin phenotype; the collection rate of cord blood versus DB; and the types of and reasons for errors.

METHODS

Cord blood samples for 6904 newborns were analyzed by electrophoresis in a large hospital laboratory. DB samples on the same cohort were analyzed by isoelectric focusing in a state public health laboratory.

RESULTS

Interlaboratory concordance was 99.4% for 6904 matched specimen pairs, which included 27 disease and 596 carrier phenotypes. In 42 pairs, discordances for potential disease phenotypes occurred with cord blood samples. Errors involving carrier phenotypes occurred in 15 cord blood samples and 14 DB samples. Inconclusive results requiring repeat testing occurred more often in the cord blood testing system (92) than in the DB system (23). Clerical transcriptions and limitations of the techniques accounted for most laboratory errors. Noncompliance in sample collection occurred more frequently with cord blood (181) than DB (86).

CONCLUSIONS

Both systems are subject to errors, but are equally reliable for neonatal hemoglobinopathy screening.

Acute multiorgan failure syndrome: a potentially catastrophic complication of severe sickle cell pain episodes

The purpose of this report is to characterize the acute multiorgan failure syndrome that complicates some episodes of sickle pain. A retrospective chart review was used to identify episodes of sickle pain complicated by the acute failure of at least two of three organs: lung, liver, or kidney. The defining criteria of organ failure were established, and the clinical characteristics, laboratory values, treatment methods, and outcomes were noted in episodes that met the criteria. Seventeen episodes of acute multiorgan failure were identified in 14 patients, 10 with sickle cell anemia and 4 with hemoglobin SC disease. Most episodes occurred during a pain event that was unusually severe for the patient. The onset of organ failure was associated with fever, rapid fall in hemoglobin level and platelet count, nonfocal encephalopathy, and rhabdomyolysis. Bacterial cultures were negative in all but four episodes. Aggressive transfusion therapy was associated with survival and with rapid recovery of organ function in all but one episode. The syndrome developed in patients who had previously exhibited relatively mild disease with little evidence of chronic organ damage and relatively high hemoglobin values in steady state. Acute multiorgan failure syndrome is a severe, life-threatening complication of pain episodes in patients with otherwise mild sickle cell disease. The syndrome appears to be reversed with prompt, aggressive transfusion therapy. High baseline hemoglobin levels may represent a predisposing factor.

Sustained attention and inhibitory control in children with sickle cell syndrome

Comparing sustained attention and inhibitory control among youth with sickle cell syndrome (SCS) and nondiseased sibling controls, this study found significant differences in multiple components of attention and inhibitory control as a function of chronological age. Older SCS youth were found to have increased attention and reflectivity. Although it has been argued that SCS youth without overt neurological impairments might evidence microvascular infarction, the present study, which employed commonly utilized neurocognitive and behavioral measures, does not lend support to the notion of generalized deficits in the absence of specific laboratory findings. Disease parameters including hemoglobin levels, days hospitalized, and emergency room visits were not significantly correlated with performance on any of the measures. Within the limitations of this particular study, results were interpreted to refute the notion of disease-related neurocognitive impairments for SCS youth. Further, the development of attentional skills for SCS youth is suggested to proceed similarly to that of normally developing youth.

Alpha 4 beta 1-integrin expression on sickle reticulocytes: vascular cell adhesion molecule-1-dependent binding to endothelium

Important complications in sickle cell anemia occur secondary to vascular occlusion, which is postulated to be initiated by interactions of erythrocytes with vascular endothelial cells. In patients with sickle cell anemia, up to 25% of reticulocytes express the alpha 4 beta 1-integrin complex. Furthermore, erythrocytes from patients with sickle cell anemia bind to endothelial cells activated by tumor necrosis factor alpha via (TNF alpha) via interactions between erythrocyte alpha 4 beta 1 and endothelial cell vascular cell adhesion molecule-1 (VCAM-1). Thus, binding of alpha 4 beta 1-expressing reticulocytes to cytokine-activated endothelial cells may initiate vascular complications in sickle cell anemia and perhaps other hemolytic anemias during episodes of infection and inflammation.

Thrombospondin from activated platelets promotes sickle erythrocyte adherence to human microvascular endothelium under physiologic flow: a potential role for platelet activation in sickle cell vaso-occlusion

Adherence of erythrocytes to vascular endothelium likely contributes to the pathophysiology of episodic vascular occlusion in patients with sickle cell disease (SCD). In addition, coagulation activation has been reported in sickle patients during complications such as pain episodes. To test the hypothesis that platelet activation contributes to sickle erythrocyte binding, we investigated whether factors released from activated sickle platelets promote adherence of sickle erythrocytes to human microvascular endothelial cells (MEC) under flow conditions. Activated sickle platelet supernatant (ASPS) promoted high levels of sickle erythrocyte adherence to MEC (55.4 +/- 3.9 erythrocytes/mm2) but only moderate adherence of normal erythrocytes to MEC (14.1 +/- 0.7 erythrocytes/mm2). When MEC were incubated with an antibody (OKM5) against CD36 (a thrombospondin [TSP] receptor), platelet supernatant mediated sickle erythrocyte adherence was inhibited 86%, suggesting that TSP participated in the adherence. To further define the role of TSP in adherence, additional studies using purified TSP were performed. At a concentration of 0.2 micrograms/mL TSP in serum-free media (SFM), sickle erythrocyte adherence to MEC was 33.9 +/- 2.7 erythrocytes/mm2 and sixfold greater than either sickle erythrocyte adherence in the absence of TSP or normal erythrocyte adherence in the presence of TSP. Doubling the concentration of TSP to 0.4 micrograms/mL proportionally increased adherence of sickle erythrocytes. Incubation of MEC with OKM5 or anti-alpha v monoclonal antibodies inhibited TSP-mediated sickle erythrocyte adherence more than 95%. These data suggest that activated platelet release factors, including alpha-granule TSP, which promote receptor-mediated sickle erythrocyte adherence to microvascular endothelium. Such factors released during in vivo platelet activation could contribute to vaso-occlusive complications by promoting erythrocyte adherence and microvascular occlusion.