Droplet digital PCR (ddPCR) is a laboratory method used to count how much of a specific DNA sequence is in a sample. The sample is first divided into thousands of tiny droplets suspended in oil. Each droplet acts like its own small test.
Some droplets will contain no target DNA, some will contain one copy, and others may contain more. During the test, the DNA inside each droplet is copied. If a droplet contains the target DNA, it produces a fluorescent signal that can be detected at the end of the process.
Each droplet is then checked for light and classified as either “positive” (DNA detected) or “negative” (no DNA detected). By counting how many droplets are positive and how many are negative, the test can accurately calculate the total amount of target DNA in the original sample.
Because ddPCR counts DNA directly rather than comparing it to reference samples, it provides an exact measurement without needing external standards (as needed for qPCR). But it is still good to run a small set of standards alongside unknowns to make sure your ddPCR assay is operating as expected.
