Towards a point-of-care strip test to diagnose sickle cell anemia

Abstract

A rapid test to identify patients with sickle cell disease could have important benefits in low-resource settings. Sickle cell anemia (SCA) affects about 300,000 newborns each year, the majority of whom are born in sub-Saharan Africa. Low-cost therapies are available to treat SCA, but most countries in sub-Saharan Africa lack robust neonatal screening programs needed to identify patients in need of treatment. To address this need, we developed and evaluated a competitive lateral flow assay that identifies patients with SCA (genotype HbSS) in 15 minutes using undiluted whole blood. A small volume of blood (0.5 μL– 3 μL) is mixed with antibody-coated blue latex beads in a tube and applied to the strip. Strips are then placed in a well of running buffer and allowed to run for 10 minutes. Laboratory evaluation with samples containing different proportions of hemoglobin A (HbA) and hemoglobin S (HbS) indicated that the test should enable identification of SCA patients but not persons with sickle cell trait (SCT). We evaluated the test using 41 samples from individuals with SCA, SCT, and normal blood. With visual inspection or quantitative analysis, we found a 98% accuracy when differentiating SCA from normal and SCT samples as a group (90% sensitivity and 100% specificity for identifying SCA). This work demonstrates important steps towards making a lateral flow test for hemoglobinopathies more appropriate for point-of-care use; further work is needed before the test is appropriate for clinical use.

HemoTypeSC, a low-cost point-of-care testing device for sickle cell disease: Promises and challenges

“…Several POCT devices for SCD have recently been developed based on different diagnostic principles including differential erythrocyte density [13], differential mobility of Hb S and Hb A through filter paper [14] and a polyclonal antibody-based capture immunoassay [15]. All of these have their limitations either because they require instrumentation as an integral part of the procedure to achieve maximum specificity and sensitivity or because of limited accuracy [16]. More recently, a new POCT (HemoTypeSC) was developed, based on monoclonal antibodies (MAb) that differentiate normal adult haemoglobin (HbA), sickle haemoglobin (HbS) and haemoglobin C (HbC) [17].…”

To test or not: occurrence of sickle cell trait and assessment of the awareness toward its screening among patients attending Magale Health Center IV, Namisindwa District, Eastern Uganda

“…Further, the PPV and NPV were 100% and 98.30%, respectively. The sensitivity of the rapid sickle cell (dithionate qualitative solubility test) is low compared to the 84% of a density-based test using aqueous multiphase systems done in Zambia, 25 93% and 94% among children and post-partum women, respectively, in a study conducted in Angola, 19 98.4% sensitivity using an immunoassay, 14 , 26 and 99% using the Sickle SCAN™ test (BioMedomics, Durham, NC, USA). 12 This assay has demonstrated a low sensitivity, which is attributed to interfering reactivity due to other Hb variants, particularly hemoglobin C (HbC)-Harlem and fetal hemoglobin (HbF).…”

“…8 This has necessitated tests that are inexpensive, reliable, rapid and fieldable. 12 , 14 – 15 Cognizant to these, point-of-care testing (PoCT) has been explored, and is hoped to avert preventable morbidities and mortalities. There are varied PoCT assays and techniques, notable among these are: SICKLEDEX ® (Streck, Omaha, NE, USA) that relies on the solubility differences in the HbA and sickle hemoglobin (HB-S) molecules, 16 and the sickle cell hemoglobin-S (dithionate qualitative solubility) test (Bio Lab Diagnostics India Private Limited, Mumbai, Maharashtra, India) that is based on Hb solubility testing.…”

“…There are varied PoCT assays and techniques, notable among these are: SICKLEDEX ® (Streck, Omaha, NE, USA) that relies on the solubility differences in the HbA and sickle hemoglobin (HB-S) molecules, 16 and the sickle cell hemoglobin-S (dithionate qualitative solubility) test (Bio Lab Diagnostics India Private Limited, Mumbai, Maharashtra, India) that is based on Hb solubility testing. 17 To ascertain their diagnostic use, validation was conducted, 12 , 15 , 18 , 19 and HB-S-PoCT was found to be practical in a resource-limited setting. For example, a paper-based validation test in a cohort of 159 newborns in Angola reported HB-S diagnostic sensitivity of 81.8% and specificity of 83.3%; while in the USA, a sensitivity of 94.2%, specificity of 97.7% and an overall diagnostic accuracy of 96.9% was reported.…”

Therapeutic angiogenesis as a treatment for Coronary Artery Occlusions

“…These immunoassays can accurately detect the presence of different hemoglobin variants and can discriminate SCA from SCT and healthy blood. 30,31 Early diagnosis is essential to reduce the risk of death from life-threatening SCA complications. Newborn screening in developed countries has allowed early intervention and treatment of SCA, resulting in the reduction of childhood mortality and improvement in the quality of life of adults.…”