Determinants of the haemoglobin level in patients with sickle cell disease living in sub-Saharan Africa: Major impact of the country of residence and independent effects of leucocyte and platelet counts and haemolysis.

The degree of anaemia in sickle cell disease (SCD) is a well-known contributor to morbidity and mortality. We aimed to explore the factors affecting haemoglobin (Hb) level in African SCD patients, considering haemolysis biomarkers (LDH and bilirubin level, and reticulocyte count), leucocyte and platelet counts and socio-demographic characteristics (gender, age group, country of residence and BMI). The research was part of the CADRE multinational cohort and involved 3699 SCD patients living in Mali, Senegal, Ivory Coast, Democratic Republic of Congo, Gabon and Cameroon: 2936 SS/Sß0, 587 SC and 176 Sß + patients with median Hb level of 8, 11.3 and 11.2 g/dL respectively (p < 0.001). In multivariate analysis conducted in 1394 SS/Sß0 patients, living in Cameroon, female gender, lower BMI, higher haemolysis markers (especially LDH) and higher leucocyte and platelet counts were independently associated with lower Hb level (all p < 0.05). In 497 SC and 156 Sß + patients, female gender (p < 0.001), lower BMI (p < 0.05) and higher platelet counts (p < 0.001) were independently associated with lower Hb level. Anaemia in African SCD patients is not only associated with haemolysis but also with the country of residence, lower BMI and leucocyte or platelet counts which might reflect inflammation related to infectious burden in the region.

Prevalence and correlates of growth failure in young African patients with sickle cell disease.

Growth failure (GF) in children with sickle cell disease (SCD) tends to decline in high-income countries, but data are lacking in sub-Saharan Africa. We performed a cross-sectional study nested in the CADRE (Cœur, Artères et DREpanocytose) cohort in Mali, Senegal, Cameroon, Gabon and the Ivory Coast. SCD patients and healthy controls aged 5-21 years old were recruited (n = 2583). Frequency of GF, defined as a height, weight or body mass index below the 5th percentile on World health Organization growth charts, was calculated. We assessed associations between GF and SCD phenotypic group, clinical and biological characteristics and history of SCD-related complications. GF was diagnosed in 51% of HbSS, 58% of HbSß0 , 44% of HbSC, 38% of HbSß+ patients and 32% of controls. GF in patients was positively associated with parents' lower education level, male sex, age 12-14 years, lower blood pressure, HbSS or HbSß0 phenotypes, icterus, lower haemoglobin level, higher leucocyte count and microalbuminuria. No association was found between GF and clinical SCD-related complications. In sub-Saharan Africa, GF is still frequent in children with SCD, especially in males and during adolescence. GF is associated with haemolysis and microalbuminuria, but not with the history of SCD-related clinical complications.

Degree of anemia, indirect markers of hemolysis, and vascular complications of sickle cell disease in Africa.

The hyperhemolysis paradigm that describes overlapping "hyperhemolytic-endothelial dysfunction" and "high hemoglobin-hyperviscous" subphenotypes of sickle cell disease (SCD) patients is based on North American studies. We performed a transversal study nested in the CADRE cohort to analyze the association between steady-state hemolysis and vascular complications of SCD among sub-Saharan African patients. In Mali, Cameroon, and Ivory Coast, 2407 SCD patients (1751 SS or sickle ß-zero-thalassemia [Sß0], 495 SC, and 161 sickle ß+-thalassemia [Sß+]), aged 3 years old and over, were included at steady state. Relative hemolytic intensity was estimated from a composite index derived from principal component analysis, which included bilirubin levels or clinical icterus, and lactate dehydrogenase levels. We assessed vascular complications (elevated tricuspid regurgitant jet velocity [TRV], microalbuminuria, leg ulcers, priapism, stroke, and osteonecrosis) by clinical examination, laboratory tests, and echocardiography. After adjustment for age, sex, country, and SCD phenotype, a low hemoglobin level was significantly associated with TRV and microalbuminuria in the whole population and with leg ulcers in SS-Sß0 adults. A high hemolysis index was associated with microalbuminuria in the whole population and with elevated TRV, microalbuminuria, and leg ulcers in SS-Sß0 adults, but these associations were no longer significant after adjustment for hemoglobin level. In conclusion, severe anemia at steady state in SCD patients living in West and Central Africa is associated with elevated TRV, microalbuminuria, and leg ulcers, but these vascular complications are not independently associated with indirect markers of increased hemolysis. Other mechanisms leading to anemia, including malnutrition and infectious diseases, may also play a role in the development of SCD vasculopathy.

Reference intervals for serum cystatin C and serum creatinine in an adult sub-Saharan African population.

BACKGROUND: Serum cystatin C (SCysC) and serum creatinine (SCr) are two biomarkers used in common practice to estimate the glomerular filtration rate (GFR). For SCysC and SCr to be used in a given population, normal values need to be determined to better assess patients. This study aimed to determine SCysC and SCr reference intervals (RIs) in a Cameroonian adult population and factors susceptible of influencing them. METHODS: We carried-out a cross-sectional study from November 2016 to May 2017 in Yaoundé, Cameroon. Participants were Cameroonians aged 18 years and above, residing inside the country and found in good health at study inclusion. SCysC and SCr were determined by particle-enhanced turbidimetric immunoassay standardized against the ERM-DA471/IFCC reference material and by the IDMS reference modified Jaffe kinetic method, respectively. RIs were determined using the 2.5th and 97.5th percentiles and their respective 90% confidence intervals (CIs). The quantile regression served to identify potential factors likely influencing SCysC and SCr values. RESULTS: We included 381 subjects comprising 49.1% females.. RIs for SCysC varied between 0.57 (90%CI: 0.50-0.60) and 1.03 mg/L (90%CI: 1.00-1.10) for females, and from 0.70 (90%CI: 0.60-0.70) to 1.10 mg/L (90%CI: 1.10-1.20) for males. Concerning SCr, its RIs ranged from 0.58 (90%CI: 0.54-0.61) to 1.08 mg/dL (90%CI: 1.02-1.21) for females, and from 0.74 (90%CI: 0.70-0.80) to 1.36 mg/dL (90%CI: 1.30-1.45) for males. Men had significantly higher SCysC and SCr values than women (p <  0.001). Likewise, subjects aged 50 years and above had higher SCysC values in comparison to younger age groups (p <  0.001), which was not the case for SCr values (p = 0.491). Moreover, there was a positive and significant correlation between SCysC and SCr in women (ρ = 0.55, p < 0.001), in men (ρ = 0.39, p < 0.001) and globally (ρ = 0.58; p < 0.001). Furthermore, the sex influenced both biomarkers' values across all quantile regression models while age and body surface area (BSA) influenced them inconsistently. CONCLUSION: This study has determined serum cystatin C and serum creatinine reference intervals in an adult Cameroonian population, whose interpretations might take into account the patient's sex and to a certain extent, his/her age and/or BSA.

Simple noninvasive tests for liver fibrosis diagnosis in sub-Saharan African adults with chronic viral hepatitis B or C: A cross sectional study in Cameroon.

BACKGROUND AND AIMS: This study aimed at measure the correlation between simple less expensive and noninvasive tests for liver fibrosis and Fibrotest among patients with chronic hepatitis B (HBV) or C (HCV) in resource-limited settings. MATERIALS AND METHODS: This was a cross-sectional study conducted at the Centre Pasteur of Cameroon among adults with chronic HBV or HCV infection. The correlation between aspartate aminotransferase to platelet ratio index(APRI), the gamma-glutamyl transferase to platelet ratio (GPR), and Fibrosis-4 score (FIB-4); and Fibrotest was assessed using the Spearman rank test providing the rho (ρ) coefficient of correlation. RESULTS: Of the 52 patients (mean age: 49 years, males: 51.9%) included, 52% were infected with HBV (n = 27). The APRI, GPR, FIB-4, and Fibrotest median scores (25th-75th percentiles) were: 0.37 (0.25-0.64), 0.34 (0.20-1.45), 1.49 (0.88-3.12), and 0.43 (0.21-0.80), respectively. The correlation with Fibrotest were: APRI (ρ = 0.678, p value < 0.0001), GPR (ρ = 0.621, p value < 0.0001) and FIB-4 (ρ = 0.772, p value < 0.0001). CONCLUSIONS: This study found a significant correlation between APRI, GPR and FIB-4; and Fibrotest among patients with chronic HBV or HCV infection in Cameroon. FIB-4 appeared as the diagnosis method with the strongest correlation with Fibrotest.

Investigations of Kidney Dysfunction-Related Gene Variants in Sickle Cell Disease Patients in Cameroon (Sub-Saharan Africa).

BACKGROUND: Renal dysfunctions are associated with increased morbidity and mortality in sickle cell disease (SCD). Early detection and subsequent management of SCD patients at risk for renal failure and dysfunctions are essential, however, predictors that can identify patients at risk of developing renal dysfunction are not fully understood. METHODS: In this study, we have investigated the association of 31 known kidney dysfunctions-related variants detected in African Americans from multi-ethnic genome wide studies (GWAS) meta-analysis, to kidney-dysfunctions in a group of 413 Cameroonian patients with SCD. Systems level bioinformatics analyses were performed, employing protein-protein interaction networks to further interrogate the putative associations. RESULTS: Up to 61% of these patients had micro-albuminuria, 2.4% proteinuria, 71% glomerular hyperfiltration, and 5.9% had renal failure. Six variants are significantly associated with the two quantifiable phenotypes of kidney dysfunction (eGFR and crude-albuminuria): A1CF-rs10994860 (P = 0.02020), SYPL2-rs12136063 (P = 0.04208), and APOL1 (G1)-rs73885319 (P = 0.04610) are associated with eGFR; and WNT7A-rs6795744 (P = 0.03730), TMEM60-rs6465825 (P = 0.02340), and APOL1 (G2)-rs71785313 (P = 0.03803) observed to be protective against micro-albuminuria. We identified a protein-protein interaction sub-network containing three of these gene variants: APOL1, SYPL2, and WNT7A, connected to the Nuclear factor NF-kappa-B p105 subunit (NFKB1), revealed to be essential and might indirectly influence extreme phenotypes. Interestingly, clinical variables, including body mass index (BMI), systolic blood pressure, vaso-occlusive crisis (VOC), and haemoglobin (Hb), explain better the kidney phenotypic variations in this SCD population. CONCLUSION: This study highlights a strong contribution of haematological indices (Hb level), anthropometric variables (BMI, blood pressure), and clinical events (i.e., vaso-occlusive crisis) to kidney dysfunctions in SCD, rather than known genetic factors. Only 6/31 characterised gene-variants are associated with kidney dysfunction phenotypes in SCD samples from Cameroon. The data reveal and emphasise the urgent need to extend GWAS studies in populations of African ancestries living in Africa, and particularly for kidney dysfunctions in SCD.

High prevalence of anti-D antibodies among women of childbearing age at Centre Pasteur of Cameroon.

We conducted a cross sectional retrospective study to determine anti-D and D-negative phenotype rates among Cameroonian women of reproductive age (15-44 years), in order to evaluate the importance of D alloimmunization. Analysis of the haematology laboratory records from January 2006 to December 2007 harvested 225 results for red blood cell alloantibody screening and 2460 D phenotypes. Anti-D rate was found to be high at 4% and not linked to women's parity. Three hundred and fifty two (14.3%) women were found to be D-negative. Anti-D rates significantly decreased with age from 18.8% among teenagers (15-19) to 7.8% among older women (35-44) (p = 0.001). The number of women submitted to both irregular antibody screening and type D phenotype determination was not strong enough (50) to analyse the link between anti-D rate and antigen D distribution in our study.

Haematological values in a healthy adult population in Yaoundé, Cameroon.

BACKGROUND: Haematological values derived from local populations are useful in laboratories to improve diagnoses for local patients. In Cameroon, these data are not yet available. Moreover, there is great variation in baseline parameters pertaining to full blood cell count among medical laboratories. OBJECTIVES: This study aimed to determine values for the complete blood cell count of a healthy adult Cameroonian population for use in locally derived ranges in our medical laboratories. METHODS: A cross-sectional study was conducted among blood donors attending three blood banks in Yaoundé from November 2015 to September 2016. We expected to obtain at least 120 venous blood samples from both men and women. Tests were performed for (1) HIV, (2) complete blood cell count, (3) hepatitis B virus, (4) malaria, (5) syphilis, (6) C-reactive protein and (7) hepatitis C virus. RESULTS: We enrolled 294 healthy participants (161 men, 133 women) aged 18 to 55 years. The median haemoglobin concentration was 135 g/L in men and 114 g/L in women (p < 0.001). The median reticulocyte count was 60 × 109/L in men and 40 × 109/L in women (p < 0.001). Significant variation by sex was observed for the platelet count. The median white blood cell count was 4.1 × 109/L in men and 4.6 × 109/L in women (p = 0.008). CONCLUSION: This study provides locally derived ranges for complete blood cell and reticulocyte counts for a healthy adult population in Yaoundé, Cameroon. These results can be used pending larger studies.

Early renal damage in patients with sickle cell disease in sub-Saharan Africa: a multinational, prospective, cross-sectional study.

BACKGROUND: Chronic kidney disease is one of the leading causes of mortality in patients with sickle cell disease. However, it has been almost exclusively studied in patients with the SS phenotype and in high-income countries, despite more than 80% of patients living in Africa. We looked for the determinants of glomerulopathy in a multinational cohort of patients with sickle cell disease of different phenotypes in sub-Saharan Africa. METHODS: In the CADRE cohort, we prospectively included patients 3 years and older with sickle cell disease of all haemoglobin phenotypes in Cameroon, Côte d'Ivoire, Mali, and Senegal. All individuals were assessed at steady state. The main outcome of interest was albuminuria defined as a urine albumin-to-creatinine ratio of greater than 30 mg/g. We investigated the clinical and biological determinants (including haemolysis markers) of albuminuria in two main phenotype groups (SS and Sß(0); SC and Sß(+)) with further stratification by age and country. FINDINGS: The study is ongoing because of follow-up. 2582 patients with sickle cell disease were included (1776 SS, 136 Sß(0), 511 SC, and 159 Sß(+)). 644 patients with the SS and Sß(0) phenotypes (33·7%, 95% CI 31·6-35·8) and 110 with the SC and Sß(+) phenotypes (16·4%, 13·6-19·2) had albuminuria. In the SS and Sß(0) group, albuminuria was detected in 144 (27%) of 527 children younger than 10 years and its frequency increased with age (29 [48%] of 60 patients aged >40 years). Multivariable analysis showed that albuminuria was associated with age (odds ratio 1·43, 95% CI 1·20-1·71; p<0·0001), female sex (1·35, 1·02-1·82; p=0·045), low haemoglobin (0·79, 0·66-0·93; p=0·006), high lactate dehydrogenase concentrations (1·33, 1·14-1·58; p=0·0009), and, using Côte d'Ivoire as the reference, Mali (2·49, 1·64-3·79; p=0·042) and Cameroon (1·59, 1·01-2·51; p=0·0007) in patients with the SS and Sß(0) phenotypes. The magnitude of the association of albuminuria with haemoglobin and lactate dehydrogenase concentrations increased with age. In the SC and Sß(+) patients, only low haemoglobin (0·69, 0·48-0·97; p=0·029), high blood pressure (1·63, 1·17-2·27; p=0·0017), and Mali (3·75, 1·75-8·04; p<0·0001) were associated with albuminuria. INTERPRETATION: Hyperhaemolysis is associated with albuminuria, with an age-dependent effect, in the SS and Sß(0) phenotypes only, suggesting a different pathological mechanism for glomerular disease in the patients with SC and Sß(+) phenotypes. However, both phenotypes are associated with a high prevalence of albuminuria in childhood. Therefore, screening for albuminuria is advised in African children with sickle cell disease to detect early renal damage. FUNDING: Paris Cité Sorbonne University (GrEX project) and Cardiology and Development.

Haematological values in a healthy adult population in Yaoundé, Cameroon

Background: Haematological values derived from local populations are useful in laboratories to improve diagnoses for local patients. In Cameroon, these data are not yet available. Moreover, there is great variation in baseline parameters pertaining to full blood cell count among medical laboratories.Objectives: This study aimed to determine values for the complete blood cell count of a healthy adult Cameroonian population for use in locally derived ranges in our medical laboratories.Methods: A cross-sectional study was conducted among blood donors attending three blood banks in Yaoundé from November 2015 to September 2016. We expected to obtain at least 120 venous blood samples from both men and women. Tests were performed for (1) HIV, (2) complete blood cell count, (3) hepatitis B virus, (4) malaria, (5) syphilis, (6) C-reactive protein and (7) hepatitis C virus.Results: We enrolled 294 healthy participants (161 men, 133 women) aged 18 to 55 years. The median haemoglobin concentration was 135 g/L in men and 114 g/L in women (p < 0.001). The median reticulocyte count was 60 × 109/L in men and 40 × 109/L in women (p < 0.001).Significant variation by sex was observed for the platelet count. The median white blood cell count was 4.1 × 109/L in men and 4.6 × 109/L in women (p = 0.008). Conclusion: This study provides locally derived ranges for complete blood cell and reticulocyte counts for a healthy adult population in Yaoundé, Cameroon. These results can be used pending larger studies