Abstract
BackgroundSickle cell disease (SCD) accounts for 5% of mortality in African children aged < 5 years. Improving the care management and quality of life of patients with SCD requires a reliable diagnosis in resource-limited settings. We assessed the diagnostic accuracy of the rapid Sickle SCAN® point-of-care (POC) test for SCD used in field conditions in two West-African countries.MethodsWe conducted a case-control study in Bamako (Mali) and Lomé (Togo). Known cases of sickle cell disease (HbSS, HbSC), trait (HbAS), HbC heterozygotes (HbAC) and homozygous (HbCC), aged ≥6 months were compared to Controls (HbAA), recruited by convenience. All subjects received both an index rapid POC test and a gold standard (high-performance liquid chromatography in Bamako; capillary electrophoresis in Lomé). Personnel conducting tests were blinded from subjects’ SCD status. Sensitivity and specificity were calculated for each phenotype. Practicality was assessed by local healthcare professionals familiar with national diagnostic methods and their associated constraints.ResultsIn Togo, 209 Cases (45 HbAS, 39 HbAC, 41 HbSS, 44 HbSC and 40 HbCC phenotypes) were compared to 86 Controls (HbAA). 100% sensitivity and specificity were observed for AA Controls and HbCC cases. Estimated sensitivity was 97.7% [95% confidence interval: 88.0–99.9], 97.6% [87.1–99.9%], 95.6% [84.8–99.5%], and 94.9% [82.7–99.4], for HbSC, HbSS, HbAS, and HbAC, respectively. Specificity exceeded 99.2% for all phenotypes. Among 160 cases and 80 controls in Mali, rapid testing was 100% sensitive and specific. Rapid testing was well accepted by local healthcare professionals.ConclusionRapid POC testing is 100% accurate for homozygote healthy people and excellent (Togo) or perfect (Mali) for sickle cell trait and disease patients. In addition to its comparable diagnostic performance, this test is cheaper, easier to implement, and logistically more convenient than the current standard diagnostic methods in use. Its predictive value indicators and diagnostic accuracy in newborns should be further evaluated prior to implementation in large-scale screening programs in resource-limited settings where SCD is prevalent.
Highlights
Sickle cell disease (SCD) accounts for 5% of mortality in African children aged < 5 years
In SCD, mutations occurring on the gene encoding for the hemoglobin (Hb) β chain are transmitted in a recessive way, with an impact on the structural, functional and rheological properties of the erythrocyte [3]. 75.5% of the SCD cases worldwide occur in Sub-Saharan Africa
Our study provides new insights into the African operational considerations of using this point-of-care (POC) device under real field conditions that could have been different from those recommended by the manufacturer
Summary
Sickle cell disease (SCD) accounts for 5% of mortality in African children aged < 5 years. We assessed the diagnostic accuracy of the rapid Sickle SCAN® point-of-care (POC) test for SCD used in field conditions in two West-African countries. Sickle Cell Disease (SCD) is the most common inherited blood disorder worldwide, accounting for 5% of the mortality in African children < 5 years of age [1, 2]. 75.5% of the SCD cases worldwide occur in Sub-Saharan Africa. The most common and severe form of SCD is the homozygous HbSS phenotype (sickle cell anaemia) inherited from both parents [2, 3]. Other forms of SCD include the compound heterozygotes HbSC disease and HbS/βthalassaemia [4]. HbC homozygotes and heterozygotes are usually well and these are not forms of sickle cell disease [5]
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