DNA testing for sickle cell anemia in Africa: Implementation choices for the Democratic Republic of Congo.

peer reviewed[en] BACKGROUND: Hemoglobin-based tests form the reference diagnostic test for SCA. In limited resource countries, these tests face limitations including cost, low sensitivity due to recurrent transfusions in endemic malaria region, and interference from fetal hemoglobin in neonatal diagnostic. This study aimed at adapting DNA-based SCA tests to limited resource countries and evaluating the economic benefit. METHODS: 338 participants were recruited in the Democratic Republic of Congo, sorted in 3 cohorts based on venous blood, umbilical cord blood (UCB) and buccal swab sampling. RFLP was performed to identify mutated allele. The feasibility and technical validity of this RFLP was evaluated for specimens collected on DBS cards and on EDTA tubes. RFLP on DBS stored at room temperature was regularly repeated to assess sample conservation. Finally, the cost analysis was performed. RESULTS: DBS cards yielded identical results to extracted DNA. Repeated testing returned the same result after four years. The DBS-based test performed on UCB or on buccal swab had a sensitivity and a precision of 100%. Cost comparison indicated that our approach costs half price of the widely used isoelectrofocussing of hemoglobin. CONCLUSION: The implemented DNA-based test approach overcomes the limitations faced by hemoglobin-based tests, while being more affordable. We propose to implement the RFLP test as a first line diagnostic test after transfusion and as second tiers for newborn screening. However, users should be aware that this test is unable to differentiate HbC from HbS or identify other point mutation of gene deletion of HBB gene.Médecine Génomique en Wallonie (WALGE/ED)3. Good health and well-bein

Clinical and biological profile of Sickle Cell Anemia children in a rural area in Central Africa.

peer reviewed[en] BACKGROUND: Sickle Cell Anemia (SCA) is the most common genetic disease worldwide caused by a single mutation in the gene HBB. The disease severity is very variable and depends on many factors. We evaluated the clinical and biological profile of sickle cell anemia children in rural Central Africa. METHODS: This cross-sectional study was conducted in the Hôpital Saint Luc de Kisantu, located 120 km away from Kinshasa-DR Congo in an area of 35 km around Kisantu with a population of roughly 80 000 individuals. We included SCA patients aged 6 months to 18 years. We collected clinical and hematological data. The SCA scoring system proposed by Adegoke et al. in 2013 was applied to determine the disease severity. We searched for factors associated to the disease severity. RESULTS: This study included 136 patients, 66 males and 70 females (sex-ratio M/F 0.94). The mean severity score was 8.21 ± 5.30 (ranges 0-23). Fifty-nine (43.4%) children had mild disease, 62 (45.6%) moderate and 15 (11%) severe disease. Girls had higher levels of HbF than boys (p = 0.003). An inverse correlation was observed between fetal hemoglobin and the disease severity (p = 0.005, r -0.239, IC95% -6.139; -1.469). Some factors such age influence the occurrence of certain chronic complications such as avascular bone necrosis. CONCLUSION: In conclusion, the disease severity of SCA depends on multiple factors. In this study, fetal hemoglobin was the main modulator of the disease severity. These data may also serve as a baseline to initiate HU treatment in this setting

Value of DNA testing in the diagnosis of sickle-cell anemia in childhood in an environment with a high prevalence of other causes of anemia.

peer reviewed[en] BACKGROUND: Sickle-cell anemia (SCA) is the most common genetic disease worldwide caused by a single mutation in the gene HBB. DNA testing can help to clarify the diagnosis when Hb electrophoresis is inconclusive. We evaluated the usefulness and feasibility of DNA-based diagnosis of SCA in rural Central Africa. METHODS: This is a cross-sectional study conducted from November 2016 to end October 2017 in the Hôpital Saint Luc de Kisantu, located 120 km from Kinshasa. This hospital offers the management of SCA patients, mainly identified using the Sickling test (Emmel test) combined with clinical features. We included patients aged 6 months to 18 years locally diagnosed as SCA, and we collected clinical and hematological data. All patients were offered Hb electrophoresis and DNA testing at the Center for Human Genetics of the University of Kinshasa. RESULTS: This study included 160 patients. Hemoglobin capillary electrophoresis suggested that 136 (85%) were homozygote SS, 13 (8.1%) were heterozygote (AS), and 11 (6.9%) were homozygote normal (AA). DNA testing confirmed these electrophoresis findings, with the exception of four patients, two AS in electrophoresis were found SS due to recent transfusion, and two SS in electrophoresis were found AS because they have compound heterozygous form S/β°-thalassemia. The diagnosis of SCA was therefore wrongly ascertained with Emmel test in 15% of patients. CONCLUSION: This study reveals a high proportion of false-positive SCA diagnoses in a rural environment in Central Africa. This underlines the importance of DNA testing in conjunction with Hb electrophoresis

Pure de novo 17q25.3 micro duplication characterized by micro array CGH in a dysmorphic infant with growth retardation, developmental delay and distal arthrogryposis

We describe a 3-year-old girl with pure 17q25.3 duplication and a complex clinical presentation comprising psychomotor/mental retardation, growth retardation and most dysmorphic features of partial duplication 17q syndrome with, additionally, a striking distal arthrogryposis. The duplication size was maximum 2.46 MB, being thus, to the best of our knowledge, the smallest 17q25.3 duplicated portion ever reported. This defect could only be detected by microarray assays, stressing once again the pertinence of this tool in detecting cryptic rearrangements. From the findings in the present patient and in the previously reported cases with duplication within the 17q21-7q25 region, it appears that the clinical features collected from the group of patients without a complementary monosomy illustrate better the trisomy 17q phenotype, and that most dysmorphic features of the 17q duplication syndrome might largely be related to the very terminal segment extending from 17q25.3 to 17qter.status: publishe