Measuring Hemoglobin: Point-of-Care Diagnostics for Anemia and Sickle Cell Disease in Low-Resource Settings
Bond, Meaghan McNeill
Doctor of Philosophy
This thesis describes my work to develop point-of-care diagnostic tools to measure hemoglobin concentration and diagnose sickle cell disease. In an effort to set design parameters for point-of-care hemoglobin analyzers, I assessed the variability of hemoglobin, platelet count, and white blood cell count and differential in successive drops of fingerprick blood. The average percent coefficient of variation in successive drops of fingerprick blood was up to 7 times higher than in venous controls. Fluctuations in blood parameters with increasing volume of fingerprick blood are within instrument variability for volumes equal to or greater than 60 – 100 μL. These data suggest caution when using measurements from a single drop of blood. Anemia is most common in regions of the world least able to afford effective diagnostics, and affects more than 60% of children under five years old in much of sub-Saharan Africa. Current methods to measure hemoglobin suffer from a high per-test cost or low accuracy. This thesis describes a method to measure hemoglobin concentration by performing spectroscopy of blood spotted on paper using a custom, portable reader. I assess the accuracy using chromatography paper in a U.S. laboratory and in a Malawi hospital. I assess the accuracy using nitrocellulose paper in the laboratory and in oncology patients at Lyndon B. Johnson hospital in Houston, TX, with 89% of samples within ±1 g/dL of a reference standard. This method for measuring hemoglobin concentration costs <$0.01 per test. Sickle cell disease is caused by a mutation in the hemoglobin molecule and leads to severe anemia, pain, and decreased immune function. It is estimated that 75.5% of babies with sickle cell disease are born in sub-Saharan Africa, where there are few resources to diagnose and treat the disease. Additionally, high-resource settings need a rapid diagnostic capable of identifying patients with sickle cell disease upon presentation to the emergency room. This thesis describes a new competitive lateral flow test capable of distinguishing sickle cell disease from sickle cell trait and normal blood using <10 μL of blood from a fingerprick with 98% accuracy (90% sensitivity and 100% specificity for identifying sickle cell disease).