Abstract
BackgroundThe high childhood mortality and life-long complications associated with sickle cell anemia (SCA) in developing countries could be significantly reduced with effective prophylaxis and education if SCA is diagnosed early in life. However, conventional laboratory methods used for diagnosing SCA remain prohibitively expensive and impractical in this setting. This study describes the clinical validation of a low-cost paper-based test for SCA that can accurately identify sickle trait carriers (HbAS) and individuals with SCA (HbSS) among adults and children over 1 year of age.Methods and FindingsIn a population of healthy volunteers and SCA patients in the United States (n = 55) the test identified individuals whose blood contained any HbS (HbAS and HbSS) with 100% sensitivity and 100% specificity for both visual evaluation and automated analysis, and detected SCA (HbSS) with 93% sensitivity and 94% specificity for visual evaluation and 100% sensitivity and 97% specificity for automated analysis. In a population of post-partum women (with a previously unknown SCA status) at a primary obstetric hospital in Cabinda, Angola (n = 226) the test identified sickle cell trait carriers with 94% sensitivity and 97% specificity using visual evaluation (none of the women had SCA). Notably, our test permits instrument- and electricity-free visual diagnostics, requires minimal training to be performed, can be completed within 30 minutes, and costs about $0.07 in test-specific consumable materials.ConclusionsOur results validate the paper-based SCA test as a useful low-cost tool for screening adults and children for sickle trait and disease and demonstrate its practicality in resource-limited clinical settings.
Highlights
Sickle cell anemia (SCA) is the most severe and prevalent form of sickle cell disease, accounting for more than 80% of all affected births worldwide.[1, 2] sickle cell anemia (SCA) results from homozygous inheritance of a missense mutation that induces a single amino acid change in the β-globin subunit of adult hemoglobin, converting normal adult hemoglobin (HbA) into sickle hemoglobin (HbS)
We describe further development of the paper-based test and its initial clinical validation for identifying individuals with sickle cell trait (HbAS), sickle cell anemia (HbSS) and other forms of sickle cell disease (HbSC, HbSβ- thalassemia) in our research laboratory in the United States
To perform the test a sample of blood is diluted with the hemoglobin solubility buffer at a 1:10 ratio and a 20 μL droplet of this mixture is deposited onto chromatography paper (Fig 1A)
Summary
Sickle cell anemia (SCA) is the most severe and prevalent form of sickle cell disease, accounting for more than 80% of all affected births worldwide.[1, 2] SCA results from homozygous inheritance of a missense mutation that induces a single amino acid change in the β-globin subunit of adult hemoglobin, converting normal adult hemoglobin (HbA) into sickle hemoglobin (HbS). The cumulative effect of these abnormalities is an increased propensity of sickle erythrocytes to undergo intravascular lysis or trigger episodic occlusion of blood vessels. These abnormalities in turn result in systemic ischemia-reperfusion injury, chronic inflammation, activation of the coagulation system, and vascular dysfunction that induce the various clinical manifestations of SCA, giving rise to life-long morbidity and premature mortality associated with the disease.[3]. This study describes the clinical validation of a low-cost paper-based test for SCA that can accurately identify sickle trait carriers (HbAS) and individuals with SCA (HbSS) among adults and children over 1 year of age
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