Paper-Based Assays

Paper-based diagnostic test for Sickle Cell Disease (SCD). A blood sample is mixed with hemoglobin solubility buffer then deposited on paper. Sickle hemoglobin (HbS) deoxygenated by the buffer becomes insoluble and remains in the area of the initial drop, while other forms of hemoglobin remain soluble and wick laterally outwards. The resulting blood stain pattern is used to differentiate between blood samples from individuals with SCD (SS), sickle cell trait (AS), and no hemoglobinopathies (AA). The pattern can be interpreted by eye or automatically using a simple image analysis algorithm. The test identifies any sickle hemoglobin (AS and SS) with 100% sensitivity and 100% specificity for both visual and automated analysis, detects SCD (SS) with 93% sensitivity and 94% specificity for visual evaluation and 100% sensitivity and 97% specificity for automated analysis, and sickle cell trait carriers (AS) with 94% sensitivity and 97% specificity using visual evaluation. The per test cost is  <$0.25 USD. The test was validated in a population of women with previously unknown SCD status in Cabinda, Angola.

Relevant Publications:

• Piety NZ, Yang X, Kanter J, Vignes SM, George A, Shevkoplyas SS (2016) “Validation of a low-cost paper-based screening test for sickle cell anemia,” PLoS ONE, 11(1): e0144901 https://doi.org/10.1371/journal.pone.0144901

• Yang X, Kanter J, Piety NZ, Benton MS, Vignes SM, Shevkoplyas SS (2013) “A simple, rapid, low-cost diagnostic test for sickle cell disease,” Lab on a Chip, 13(8): 1464 – 1467 (back cover) https://doi.org/10.1039/C3LC41302K

• Torabian K, Lezzar D, Piety NZ, George A, Shevkoplyas SS (2017) “Substituting Sodium Hydrosulfite with Sodium Metabisulfite Improves Long-term Stability of a Distributable Paper-based Test Kit for Point-of-Care Screening for Sickle Cell Anemia,” Biosensors, 7(3): 39 https://doi.org/10.3390/bios7030039

• Piety NZ (2017) “Traveling to Angola to validate a paper-based sickle cell disease test,” IEEE Pulse Magazine, 8(3): 45 https://doi.org/10.1109/MPUL.2017.2683438

Quantitative version of the paper-based diagnostic test for SCD. Optimized solubility buffer formula combined with an improved image analysis algorithm enabled quantification of sickle hemoglobin (HbS). The standard deviation of the difference between this simple, low-cost method and conventional lab-based hemoglobin electrophoresis is only 7%, which is accurate enough to guide clinical decision making during SCD treatment. Developed using research funding from an American Heart Association predoctoral fellowship.

Relevant Publications:

• Piety NZ, Yang X, Lezzar D, George A, Shevkoplyas SS (2015) “A rapid paper-based test for quantifying sickle hemoglobin in blood samples from patients with sickle cell disease,” American Journal of Hematology, 90(6): 478 – 482 https://doi.org/10.1002/ajh.23980

Newborn sickle hemoglobin (HbS) screening assay. A modified version of the SCD diagnostic test capable of screening newborns for HbS. A self-contained filter is used to remove cellular debris (which could cause a false positive result) from the lysed blood sample prior to mixing with deoxygenation buffer and depositing the mixture on paper. Enables visible detection of HbS concentrations as low as 2% at the point-of-care. No electricity or equipment is required, and the total cost of materials and reagents is ~$2 USD per test. Developed from an idea to a laboratory proof-of-concept study to a real-world field validation in Cabinda, Angola.

Relevant Publications:

• Piety NZ, George A, Serrano S, Lanzi MR, Patel PR, Noli MP, Kahan S, Nirenberg JF, Airewele G, Shevkoplyas SS (2017) “A paper-based test for screening newborns for sickle cell disease,” Scientific Reports, 7(1): 45488 https://doi.org/10.1038/srep45488

• Piety NZ, Shevkoplyas SS (2017) “Paper-based diagnostics: rethinking conventional sickle cell screening to improve access to high-quality health care in resource-limited settings,” IEEE Pulse Magazine, 8(3): 42 – 46 https://doi.org/10.1109/MPUL.2017.2678658

Blood hemoglobin (Hb) quantification assay. A blood sample is mixed with Drabkin reagent to convert Hb to cyanmethemoglobin (a stable brown-colored compound). The mixture is deposited on chromatography paper and allowed to dry. The mean color intensity of the resulting blood stain is measured using image analysis and used to quantify Hb. The standard deviation of the difference between this simple, low-cost method and a gold standard laboratory method is only 0.62 g/dL, which is sufficiently accurate to guide clinical decision making.

Relevant Publications:

• Yang X, Piety NZ, Vignes SM, Benton MS, Kanter J, Shevkoplyas SS (2013) “Simple paper-based test for measuring blood hemoglobin concentration in resource-limited settings,” Clinical Chemistry, 59(10): 1506 – 1513 https://doi.org/10.1373/clinchem.2013.204701

3D printed paper-based patterns/devices. A novel process for patterning paper using 3D printed polycaprolactone (PCL) and wax-based filaments with low glass transition temperatures. Hydrophobic barriers are created by printing melted material through the thickness of porous paper substrates. Features extending beyond the thickness of the paper can also be printed using the same material. Enables fabrication of paper-based assays using common extrusion 3D printers instead of highly specialized wax ink printers.

Paper-based printable humidity sensors. Colorimetric assays based on the reaction of CuCl2 and CoCl2 with water molecules. Printed using a Fujifilm Dimatix Materials Printer DMP-2831. The solutions can be co-printed with other paper-based assays and used to calibrate image analysis algorithms, thereby improving the accuracy of measurements impacted by ambient humidity. Developed at the Åbo Akademi University Center for Functional Materials (FUNMAT) in Turku, Finland using research funding from a Whitaker International Program Summer Grant Award.