The Quantiplex (branched-chain DNA, or bDNA) test made by Chiron, and the NASBA (nucleic acid sequence-based assay) made by Organon Teknika also quantify HIV RNA in the blood plasma. NASBA is more commonly used in Europe than in the US. Each test has a limit of detection below which it cannot quantify HIV.

Current limits of detection for clinically available tests are 400 copies/ml for the RT-PCR test and 10,000 copies/ml for the bDNA test. Second generation tests are being developed that measure as few as 25 copies (RT-PCR) or 400 copies (bDNA). Test results, somewhat variable, are reported in copies/ml.