Health policy for sickle cell disease in Africa: experience from Tanzania on interventions to reduce under-five mortality.

Tanzania has made considerable progress towards reducing childhood mortality, achieving a 57% decrease between 1980 and 2011. This epidemiological transition will cause a reduction in the contribution of infectious diseases to childhood mortality and increase in contribution from non-communicable diseases (NCDs). Haemoglobinopathies are amongst the most common childhood NCDs, with sickle cell disease (SCD) being the commonest haemoglobinopathy in Africa. In Tanzania, 10,313 children with SCD under 5 years of age (U5) are estimated to die every year, contributing an estimated 7% of overall deaths in U5 children. Key policies that governments in Africa are able to implement would reduce mortality in SCD, focusing on newborn screening and comprehensive SCD care programmes. Such programmes would ensure that interventions such as prevention of infections using penicillin plus prompt diagnosis and treatment of complications are provided to all individuals with SCD

Haptoglobin, alpha-thalassaemia and glucose-6-phosphate dehydrogenase polymorphisms and risk of abnormal transcranial Doppler among patients with sickle cell anaemia in Tanzania.

Transcranial Doppler ultrasonography measures cerebral blood flow velocity (CBFv) of basal intracranial vessels and is used clinically to detect stroke risk in children with sickle cell anaemia (SCA). Co-inheritance in SCA of alpha-thalassaemia and glucose-6-phosphate dehydrogenase (G6PD) polymorphisms is reported to associate with high CBFv and/or risk of stroke. The effect of a common functional polymorphism of haptoglobin (HP) is unknown. We investigated the effect of co-inheritance of these polymorphisms on CBFv in 601 stroke-free Tanzanian SCA patients aged <24 years. Homozygosity for alpha-thalassaemia 3·7 deletion was significantly associated with reduced mean CBFv compared to wild-type (β-coefficient -16·1 cm/s, P = 0·002) adjusted for age and survey year. Inheritance of 1 or 2 alpha-thalassaemia deletions was associated with decreased risk of abnormally high CBFv, compared to published data from Kenyan healthy control children (Relative risk ratio [RRR] = 0·53 [95% confidence interval (CI):0·35-0·8] & RRR = 0·43 [95% CI:0·23-0·78]), and reduced risk of abnormally low CBFv for 1 deletion only (RRR = 0·38 [95% CI:0·17-0·83]). No effects were observed for G6PD or HP polymorphisms. This is the first report of the effects of co-inheritance of common polymorphisms, including the HP polymorphism, on CBFv in SCA patients resident in Africa and confirms the importance of alpha-thalassaemia in reducing risk of abnormal CBFv

Ready-to-use food supplement, with or without arginine and citrulline, with daily chloroquine in Tanzanian children with sickle-cell disease: a double-blind, random order crossover trial

Background: Sickle cell disease increases malnutrition risk. Low arginine and nitric oxide [NO] bioavailability are implicated in sickle-related morbidity. Simple interventions are required, especially in low-income settings. We aimed to test the hypotheses: (1) supplementary arginine, citrulline and daily chloroquine increases bioavailable arginine and flow-mediated-dilatation (FMDmax%; a measure of NO-dependent endothelial function), and (2); protein energy supplementation in the form of ready-to-use supplementary-food (RUSF) improves nutritional status in children with sickle cell disease. Methods: A random-order, double-blind, cross-over trial with two four-month intervention periods (each followed by four-months wash-out) was conducted in Dar-es-Salaam, Tanzania. 119 children aged 8-12 years, naïve to hydroxyurea, were enrolled from the Muhimbili National Hospital Sickle Cohort. The random order sequence and allocation codes were generated centrally. Two formulations of RUSF (500kcal/day) were tested: ‘basic’ with weekly chloroquine (150/225mg base, depending on weight) (RUSF-b) and ‘vascular’ (RUSF-v) fortified with arginine, citrulline designed to achieve mean intakes of 0.2g/0.1g/kg/day and daily chloroquine (max 3mg base/kg/day). The primary outcomes of the comparison of the 2 RUSF formulations were mean FMDmax%, mean plasma arginine to ornithine ratio and mean plasma arginine to asymmetric-di-methylated-arginine (ADMA) ratio. The primary outcomes of the combined effect of both RUSF interventions were mean height and body mass index for age z-scores with analysis by intention to treat. Trial registration: ISRCTN74331412 Findings: 114/119 children had complete data for all reported endpoints. There was no treatment effect of RUSF-v compared to RUSF-b on the ratio of arginine to ornithine (mean within individual difference -0.09, 95% CI -0.03/0.2, p=0.12), or on FMDmax% (-1.00 95% CI -2.47/0.47, p=0.18) but the arginine:ADMA ratio was significantly increased (-0.56, 95% CI -0.81/-0.31, P<0.001). In planned analyses using random effects models to estimate the effect of each intervention compared to baseline/washout, the arginine:ADMA ratio increased following both RUSF-v or RUSF-b (+86%, p<0.001; +41%, p<0.001). Similarly, FMDmax% was higher after 2 RUSF-v (+0.92, p<0.001) but not after RUSF-b intervention (+0.39, p=0.22). Adjusted for covariates, effect estimates for FMDmax% increased: RUSF-v (+1.19, p<0.001) and RUSF-b (+0.93, p=0.008). Following either intervention (RUSF-b and RUSF-v pooled) compared to baseline/wash-outs, body-mass-index-z-score (+0.091, P=0.001) and height-for-age-z-score (+0.013, P=0.081) increased. There were 71 and 81 adverse events of which 21 and 26 were serious during intervention and washout (P=0.31) in 83 participants, 1 of whom died in the 2nd washout period. Interpretation: RUSF providing 500kcal/day results in small weight gains in children with sickle cell disease. However, RUSF even without arginine and citrulline fortification improves arginine dysregulation and may improve endothelial function. Long-term studies are required to assess if these physiological effects translate to improved clinical outcomes and better growth and development in sickle cell disease

A pilot study of a non-invasive oral nitrate stable isotopic method suggests that arginine and citrulline supplementation increases whole-body NO production in Tanzanian children with sickle cell disease.

BACKGROUND: Low bioavailability of nitric oxide (NO) is implicated in the pathophysiology of sickle cell disease (SCD). We designed a nested pilot study to be conducted within a clinical trial testing the effects of a daily ready-to-use supplementary food (RUSF) fortified with arginine (Arg) and citrulline (Citr) vs. non-fortified RUSF in children with SCD. The pilot study evaluated 1) the feasibility of a non-invasive stable isotope method to measure whole-body NO production and 2) whether Arg+Citr supplementation was associated with increased whole-body NO production. SUBJECTS: Twenty-nine children (70% male, 9-11years, weight 16.3-31.3 kg) with SCD. METHODS: Sixteen children received RUSF+Arg/Citr (Arg, 0.2  g/kg/day; Citr, 0.1  g/kg/day) in combination with daily chloroquine (50 mg) and thirteen received the base RUSF in combination with weekly chloroquine (150 mg). Plasma amino acids were assessed using ion-exchange elution (Biochrom-30, Biochrom, UK) and whole-body NO production was measured using a non-invasive stable isotopic method. RESULTS: The RUSF+Arg/Citr intervention increased plasma arginine (P = .02) and ornithine (P = .003) and decreased the ratio of asymmetric dimethylarginine to arginine (P = .01), compared to the base RUSF. A significant increase in whole-body NO production was observed in the RUSF-Arg/Citr group compared to baseline (weight-adjusted systemic NO synthesis 3.38 ± 2.29 μmol/kg/hr vs 2.35 ± 1.13 μmol/kg/hr, P = .04). No significant changes were detected in the base RUSF group (weight-adjusted systemic NO synthesis 2.64 ± 1.14 μmol/kg/hr vs 2.53 ± 1.12 μmol/kg/hr, P = .80). CONCLUSIONS: The non-invasive stable isotopic method was acceptable and the results provided supporting evidence that Arg/Citr supplementation may increase systemic NO synthesis in children with SCD

Health policy for sickle cell disease in Africa: experience from Tanzania on interventions to reduce under-five mortality

Tanzania has made considerable progress towards reducing childhood mortality, achieving a 57% decrease between 1980 and 2011. This epidemiological transition will cause a reduction in the contribution of infectious diseases to childhood mortality and increase in contribution from noncommunicable diseases (NCDs). Haemoglobinopathies are amongst the most common childhood NCDs, with sickle cell disease (SCD) being the commonest haemoglobinopathy in Africa. In Tanzania, 10 313 children with SCD under 5 years of age (U5) are estimated to die every year, contributing an estimated 7 % of overall deaths in U5 children. Key policies that governments in Africa are able to implement would reduce mortality in SCD, focusing on newborn screening and comprehensive SCD care programmes. Such programmes would ensure that interventions such as prevention of infections using penicillin plus prompt diagnosis and treatment of complications are provided to all individuals with SCD

Peripheral vascular response to inspiratory breath hold in paediatric homozygous sickle cell disease.

There is increasing evidence that autonomic dysfunction in adults with homozygous sickle cell (haemoglobin SS) disease is associated with enhanced autonomic nervous system-mediated control of microvascular perfusion. However, it is unclear whether such differences are detectable in children with SS disease. We studied 65 children with SS disease [38 boys; median age 7.2 (interquartile range 5.1-10.6) years] and 20 control children without symptoms of SS disease [8 boys; 8.7 (5.5-10.8) years] and recorded mean arterial blood pressure (ABP) and daytime haemoglobin oxygen saturation (S(pO(2))). Cutaneous blood flux at rest (RBF) and during the sympathetically activated vasoconstrictor response to inspiratory breath hold (IBH) were measured in the finger pulp of the non-dominant hand using laser Doppler fluximetry. Local factors mediating flow motion were assessed by power spectral density analysis of the oscillatory components of the laser Doppler signal. The RBF measured across the two study groups was negatively associated with age (r = -0.25, P < 0.0001), ABP (r = -0.27, P = 0.02) and daytime S(pO(2)) (r = -0.30, P = 0.005). Children with SS disease had a higher RBF (P = 0.005) and enhanced vasoconstrictor response to IBH (P = 0.002) compared with control children. In children with SS disease, higher RBF was associated with an increase in the sympathetic interval (r = -0.28, P = 0.022). The SS disease status, daytime S(pO(2)) and age explained 22% of the variance in vasoconstrictor response to IBH (P < 0.0001). Our findings suggest that blood flow and blood flow responses in the skin of young African children with SS disease differ from those of healthy control children, with increased resting peripheral blood flow and increased sympathetic stimulation from a young age in SS disease. They further suggest that the laser Doppler flowmetry technique with inspiratory breath hold manoeuvre appears to be robust for use in young children with SS disease, to explore interactions between S(pO(2)), ABP and autonomic function with clinical complications, e.g. skin ulceration

Clinical epidemiology of individuals with Sickle cell anemia using Hydroxyurea at Muhimbili National Hospital, Dar Es Salaam, Tanzania

Background: The pathophysiology of sickle cell disease (SCD) is complex and involves nitric oxide depletion, increased inflammation/adhesion molecules and vaso-occlusion in addition to the chronic hemolytic anemia. This pathophysiology results in systemic clinical complications including recurrent episodes of severe pain, stroke, acute chest syndrome (ACS) and an increased susceptibility to infection. SCD severity varies among individuals and fetal hemoglobin (HbF) is known as a major modulator of the disease. To date, hydroxyurea (HU) is a known intervention that acts by increasing HbF in individuals with SCD. The increase in HbF reduces the risk of ‘sickling’ events and improves clinical outcomes. This is the first study on the use of HU in individuals with SCA in Tanzania.Methods: A case-control study to determine the proportion, indications, clinical and laboratory outcomes of SCD patients with HU use was conducted at Muhimbili National Hospital in Dar Es Salaam, Tanzania.Results: Forty-two patients with Sickle cell anemia (SCA) on HU treatment and 32 patients with SCA not on HU treatment were enrolled. The proportion of HU use by individuals with SCA at Muhimbili National Hospital was 10 per 1000. The mean HbF % was 9.8 ± 2.4 vs 6.2 ±1.4 for controls (P &lt;0.001). Thirty (71.4%) were enrolled for HU treatment due to central nervous system (CNS) events, frequent painful crises 11(26.2%) and recurrent anemia 1(2.4%). Thirty-two SCA patients (76.2%) reported improvements after being on HU for at least six months. Of these, 91% reported no history of severe pain that required hospitalizations since they started HU. Twenty patients (66.7%) out of those with CNS events reported not to have experienced convulsions after HU initiation.Conclusions: HbF was higher in patients who were on HU and had positive correlation with clinical outcomes. Further clinical trials are required to evaluate more effects of HU use among SCA individuals in Tanzania. Keywords: Sickle cell anemia, HU, Fetal hemoglobin, Tanzania

Bacteraemia in sickle cell anaemia is associated with low haemoglobin: a report of 890 admissions to a tertiary hospital in Tanzania

Bacteraemia is a leading cause of morbidity in sickle cell anaemia (SCA), but information from studies in Africa is limited. We evaluated 890 admissions from 648 SCA patients at a tertiary hospital in Tanzania. Bacteraemia was present in 43 admissions (4·8%); isolates included Staphylococcus aureus (12/43; 28%), non-Typhi Salmonella (9/43; 21%), Streptococcus pneumoniae (3/43; 7%) and Salmonella Typhi (2/43; 5%). Compared to SCA patients without bacteraemia, SCA patients with bacteraemia had significantly lower haemoglobin [71 g/l vs. 62 g/l, odds ratio 0·72 (95% confidence interval 0·56-0·91), P &lt; 0·01]. Further exploration is needed of the relationship between anaemia and bacterial infections in SCA in Africa.</p

Negative Epistasis between Sickle and Foetal Haemoglobin Suggests a Reduction in Protection against Malaria.

BACKGROUND: Haemoglobin variants, Sickle (HbS) and foetal (HbF) have been associated with malaria protection. This study explores epistatic interactions between HbS and HbF on malaria infection. METHODS: The study was conducted between March 2004 and December 2013 within the sickle cell disease (SCD) programme at Muhimbili National Hospital, Tanzania. SCD status was categorized into HbAA, HbAS and HbSS using hemoglobin electrophoresis and High Performance Liquid Chromatography (HPLC). HbF levels were determined by HPLC. Malaria was diagnosed using rapid diagnostic test and/or blood film. Logistic regression and generalized estimating equations models were used to evaluate associations between SCD status, HbF and malaria. FINDINGS: 2,049 individuals with age range 0-70 years, HbAA 311(15.2%), HbAS 241(11.8%) and HbSS 1,497(73.1%) were analysed. At enrolment, malaria prevalence was significantly higher in HbAA 13.2% compared to HbAS 1.24% and HbSS 1.34% (p<0.001). Mean HbF was lower in those with malaria compared to those without malaria in HbAA (0.43% vs 0.82%) but was the reverse in HbSS (8.10% vs 5.59%). An increase in HbF was associated with a decrease in risk of malaria OR=0.50 (95%CI: 0.28, 0.90; p=0.021) in HbAA, whereas for HbSS the risk of malaria increased OR=2.94 (1.44, 5.98; p=0.003). A similar pattern was seen during multiple visits; HbAA OR=0.52 (0.34, 0.80; p=0.003) vs HbSS OR=2.01 (1.27, 3.23; p=0.003). CONCLUSION: Higher prevalence of malaria in HbAA compared to HbAS and HbSS confirmed the protective effect of HbS. Lower prevalence of malaria in HbAA with high HbF supports a protective effect of HbF. However, in HbSS, the higher prevalence of malaria with high levels of HbF suggests loss of malaria protection. This is the first epidemiological study to suggest a negative epistasis between HbF and HbS on malaria