Dataset Information

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 ?L- 3 ?L) 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.

SUBMITTER: Bond M

PROVIDER: S-EPMC5433739 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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

Bond Meaghan M Hunt Brady B Flynn Bailey B Huhtinen Petri P Ware Russell R Richards-Kortum Rebecca R

PloS one 20170516 5

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 ...[more]

PMID: 28520780

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Project description:BackgroundNucleic acid-based amplification tests (NAAT), above all (q)PCR, have been applied for the detection of Mycobacterium leprae in leprosy cases and household contacts with subclinical infection. However, their application in the field poses a range of technical challenges. Loop-mediated isothermal amplification (LAMP), as a promising point-of-care NAAT does not require sophisticated laboratory equipment, is easy to perform, and is applicable for decentralized diagnosis at the primary health care level. Among a range of gene targets, the M. leprae specific repetitive element RLEP is regarded as highly sensitive and specific for diagnostic applications. METHODS: Our group developed and validated a dry-reagent-based (DRB) RLEP LAMP, provided product specifications for customization of a ready-to-use kit (intended for commercial production) and compared it against the in-house prototype. The assays were optimized for application on a Genie® III portable fluorometer. For technical validation, 40 "must not detect RLEP" samples derived from RLEP qPCR negative exposed and non-exposed individuals, as well as from patients with other conditions and a set of closely related mycobacterial cultures, were tested together with 25 "must detect RLEP" samples derived from qPCR confirmed leprosy patients. For clinical validation, 150 RLEP qPCR tested samples were analyzed, consisting of the following categories: high-positive samples of multibacillary (MB) leprosy patients (> 10.000 bacilli/extract), medium-positive samples of MB leprosy patients (1.001-10.000 bacilli/extract), low-positive samples of MB leprosy patients (1-1.000 bacilli/extract), endemic controls and healthy non-exposed controls; each n = 30. RESULTS: Technical validation: both LAMP formats had a limit of detection of 1.000 RLEP copies, i.e. 43-27 bacilli, a sensitivity of 92% (in-house protocol)/100% (ready-to-use protocol) and a specificity of 100%. Reagents were stable for at least 1 year at 22 °C. Clinical validation: Both formats showed a negativity rate of 100% and a positivity rate of 100% for high-positive samples and 93-100% for medium positive samples, together with a positive predictive value of 100% and semi-quantitative results. The positivity rate for low-positive samples was 77% (in-house protocol)/43% (ready-to-use protocol) and differed significantly between both formats. CONCLUSIONS: The ready-to-use RLEP DRB LAMP assay constitutes an ASSURED test ready for field-based evaluation trials aiming for routine diagnosis of leprosy at the primary health care level.

Dataset Information

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

Publications

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

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