A User-Friendly Point of Care Device, Glucose-6-Phosphate Dehydrogenase
Grant Number: 2R44AI129057-02A1
Grant Agency and Type: NIH NIAID, Phase II SBIR
Principal Investigator: Robert Harper
Disease Indication: Malaria
Malaria caused by Plasmodium vivax threatens over 2 billion people globally and sickens tens of millions annually. Radical cure for P. vivax malaria includes therapy aimed both at the acute attack (blood schizontocidal) and against future attacks (hypnozoitocidal). The only hypnozoitocide available is 8- aminoquinolines such as Primaquine or tafenoquine. However, clinicians often do not prescribe 8- aminoquinolines due to the high prevalence (8%) of individuals with various levels of inherited Glucose-6- phosphate dehydrogenase (G6PD) deficiencies, because these drugs can cause life-threatening acute hemolytic anemia in patients with moderate to severe G6PD deficits. There is an urgent need to quantify both Hgb and G6PD for patients stricken with malaria or prior to the administration of 8-aminoquinilones. All current quantitative methods for G6PD determination are laboratory-based spectrophotometric methods, requiring diluents, reagents, pipettes, and trained personnel. There are currently no commercially available point-of-care (POC) tests that can quantify both Hgb and G6PD directly from a fingerstick sample. Developing a robust, quantitative assay for field use in low resource areas is a high priority for overall malaria control and elimination.
To complete the development of the PreQuine System, we will: (1) Finalize Assay Development by Assessing Bioactive Components. Three commercially available diaphorase will be tested to ensure (a) a high degree of activity at the optimal pH, (b) long-term stability; and (c) no inhibition in the presence of maleimide; (2) Transition from Hand Assembly to Semi-Automated Assembly of Test Strips. This will be achieved by optimizing process capabilities of coating, slitting, and laminating the strips into 5-up card stock; (3) Incorporate a Temperature Correction Factor (TFC). The PreQuine system must be able to function in a working temperature of 18°C to 40°C. The TFC will be incorporated into the software and correct for temperature differences. Finally, (4) Validation of the PreQuine System. Validation for G6PD and Hgb levels will demonstrate concordance between the manufactured test strips and reference methods. Once validated and commercialized, the PreQuine System will provide a point-of-care diagnostic tool to identify G6PD-deficient individuals who cannot tolerate 8-aminoquinoline treatment, which will transform malaria treatment strategies and aid in the eradication of P.vivax and P. oval malaria.
Results and Commercialization Status:
Graph 1. is a plot of Percent Reflectance (%R) versus Glucose-6-Phosphate Dehydrogenase (G6PD) concentrations from patient samples; samples spiked with G6PD and samples that went through a freeze-thaw process to ensure the samples encompassed the analytical range of 0.8-12.5 Units G6PD /g Hgb. Reflectance values were obtained by the hand-held PreQuine Meter, and G6PD concentrations were obtained via the Pointe Scientific G6PD Spectrophotometric assay.
Graph 1. Third-degree Polynomial of Spectrophotometric Concentration of G6PD vs % Reflectance
Graph 2. is a linear regression of retrospectively calculated results from the PreQuine Meter versus results obtained by the Pointe Scientific G6PD Spectrophotometric assay. The graph reveals excellent agreement. Once we have completed the calibration software, the output will be displayed as Hgb g/dL and G6PD U/g Hgb.
Graph 2. First-order Linear Regression Spectrophotometric Concentration of G6PD vs PreQuine Meter Output Calculation