An Accurate and Rapid Color-Based Point-of-Care Assay for the Detection of Severe Anemia in Low Resource Settings

Background: Severe anemia is a leading cause of morbidity and mortality among children in low-resource countries, particulalrly in sub-Saharan Africa, where malaria is endemic and sickle cell disease is prevalent. In many low-resource regions, particularly more remote areas, laboratory diagnostics are not always readily available. The utility of available equipment can be limited by lack of technical expertise, maintenance, and trained personnel, as well as lack of affordable reagents and reliable power. In a setting where severe, life-threatening anemia is common, it is critical for providers to have access to a rapid and accurate diagnostic tool to determine which patients need acute evaluation and treatment. A simple, rapid, accurate, and disposable point-of-care assay (AnemoCheck¨) has recently been tested and published(Tyburski et al. JCI 2014, in press), Hemoglobin concentration is measured by assessing the color of a chemical solution containing hydrogen peroxide and 3,3',5,5'-tetramethylbenzidine, after mixing with 10μL blood. The AnemoCheck assay is self-contained and does not require electricity, complicated sensors, or additional equipment. The color scale of the original assay correlated well with mild anemia (Hb 9-13 g/dL) but was not designed to discriminate lower hemoglobin concentrations. Accordingly, the test was modified to allow the color scale to detect more severe anemia (Hb 2.5-9.1 g/dL), but needs to be tested in a real-world setting where severe anemia is prevalent.

Methods: The primary objective of this study was to determine whether AnemoCheck tests could measure hemoglobin concentrations at least as accurately as currently used standard laboratory techniques in low resource settings where severe anemia is common. The study was performed in the sickle cell clinic at Hospital Pedi‡trico David Bernardino, a large, public pediatric hospital in Luanda, Angola. After receiving informed consent from a parent or guardian, capillary blood was collected by fingerstick as per routine to measure hemoglobin using a BioSystems BTS-350 Hemoglobin Analyzer. A small sample of capillary blood was also collected for the AnemoCheck assay using a 10μL end-to-end capillary tube via capillary action (Sanguis Counting, Germany). Venous blood was also collected to measure hemoglobin using a calibrated hematology analyzer (Sysmex XT-2000i), which was considered the true hemoglobin concentration for comparison purposes. Hemoglobin was determined first by AnemoCheck by placing the 10μL capillary into a 2mL screw cap polypropylene tube containing the chemical reagents. The tube was then vigorously shaken and after 60 seconds, was compared to a standardized color scale and the hemoglobin concentration was determined. The AnemoCheck results were obtained and recorded before any additional machine-determined results were available, to avoid potential bias.

Results: For this pilot study, samples were collected from 40 children for hemoglobin determination by all three methods. The range of hemoglobin concentrations, based on results from the Sysmex hematology analyzer, was 4.8 – 9.2 g/dL (median 7.0). As illustrated in the Figure, the hemoglobin values obtained from the AnemoCheck assay correlated well with the Sysmex hematology analyzer results, r=0.74, p<0.0001. The AnemoCheck results were more accurate than the hemoglobin values obtained by the BioSystems Hemoglobin Analyzer (r=0.47, p=0.020), which is the primary mode of hemoglobin determination in the clinic. On average, the hemoglobin obtained by AnemoCheck was within 0.5 g/dL of the Sysmex value (range 0-1.9 g/dL), compared to the Biosystems value (absolute mean difference=0.7 g/dL, range 0-2.2 g/dL).

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Conclusions: Laboratory diagnosis of anemia is expensive and difficult in low resource settings such as Angola, where severe anemia is common and life-threatening. Our pilot data demonstrate that a novel, point-of-care, color-based assay that does not require electricity or expensive reagents is able to accurately estimate low hemoglobin concentrations. Further refinements of the AnemoCheck assay will include photographic color assessment and automated hemoglobin estimation, which will be helpful in resource-poor settings. This test has the potential to become extremely useful diagnostic tool in low resource hospitals and health centers, where sophisticated equipment and reagents may not be available.