D4 Assay (IMAGE) Duke University Caption A researcher holds a test version of the D4 Assay, which has been proven to be able to detect trace amounts of disease biomarkers. Credit Michaela Kane, Duke University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.