[1] A branched DNA assay begins with a dish or some other solid support (e.g., a plastic dipstick).
The dish is peppered with small, single stranded DNA molecules (or chains) that stick out into the solution.
Thus, small amounts of a nucleic acid can be detected and quantified without a reverse transcription step (in the case of RNA) and/or PCR.
The capture and capture-extender oligonucleotide bind to the target nucleic acid and immobilize it on a solid support.
The immobilization of the target on a solid support makes extensive washing easier, which reduces false positive results.
After binding of the target to the solid support it can be detected by branched DNA which is coupled to an enzyme (e.g. alkaline phosphatase).
[2] Despite the fact that the starting material is not preamplified, bDNA assays can detect less than 100 copies of HIV-RNA per mL of blood.