The REDI-Dx® Biodosimetry Test System consists of the REDI-Dx® gene expression assay, the DxCollect® Blood Collection Tube (BCT), the Applied Biosystems® 3500xL Dx Genetic Analyzer CS2, and REDI-Dx® Interpretative Software. The system is being developed to provide quantitative estimation of absorbed radiation dose from a patient blood sample that is collected between 1 and 7 days post-exposure. The test system is being developed to measure the relative expression of 18 genes (15 response genes and 3 normalizer genes) and to use a multi-variate algorithm to estimate absorbed dose.
After collection using the DxCollect® Blood Collection Tube (BCT), the sample would be transported to testing labs at ambient temperature. The DxCollect® solution preserves the nucleic acids within blood allowing for ambient stability up to 14 days. Upon delivery, the lab would use the REDI-Dx® Test with automated liquid handling platforms specifically designed for high volume and high throughput to perform sample processing and testing. Final analysis is performed on the ABI 3500 Dx Genetic Analyzer instrument, with results generated by REDI-Dx® Interpretive Software.
REDI-Dx® system performance is being assessed using data consisting of total body irradiation (TBI) samples and non-irradiated samples which included different ethnicities, ages, and potentially confounding conditions including burn, trauma and flu. REDI-Dx® dose estimates are anticipated to be quantitative throughout the clinically relevant range of 0 to 8 Gray (Gy).
In irradiated samples spanning the range of 0.5 Gy to 10 Gy and using time post-exposure from 24 hours to 7 days, REDI-Dx® is expected to demonstrate Positive Predictive Values of 98.8% for samples of 0.5 Gy or less and 94.5% for samples of 6.0 Gy or more.
Negative Predictive Values (NPV) and Positive Predicative Values (PPV) for treatment groups were calculated using 891 single dose irradiated samples and 950 non-irradiated samples. For all four dose ranges, the complete data set is evaluated. PPV is the proportion of samples estimated in each indicated range that have actual doses in the range. NPV is the proportion of samples estimated outside of the indicated range that have actual doses outside of the range. Irradiated samples spanned the range of 0.5 Gy to 10 Gy and time post exposure was from 6 hours to 7 days. Treatment Actions are based on recommended medical triage and treatment guidelines for acute radiation exposure. (Coleman, et. al)
The REDI-Dx® High Throughput Biodosimetry Test System is being developed to have sufficient throughput, capacity, speed and accuracy to help formulate an appropriate response to a mass-scale nuclear incident. The REDI-Dx® Biodosimetry System is targeting a quantitative range of 0 to 8 Gy and a false positive rate of less than 0.5% across different ethnicities and confounding conditions. The system is being developed to be compatible with existing clinical laboratory testing infrastructure and to deliver results in as little as 6 hours.