NASBA was developed by J Compton in 1991, who defined it as "a primer-dependent technology that can be used for the continuous amplification of nucleic acids in a single mixture at one temperature". Immediately after the invention of NASBA it was used for the rapid diagnosis and quantification of HIV-1 in patient sera. Although RNA can also be amplified by PCR using a reverse transcriptase (in order to synthesize a complementary DNA strand as a template), NASBA's main advantage is that it works under isothermal conditions – usually at a constant temperature of 41 °C or two different temperatures, depending on the primers and enzymes used. Even when two different temperatures are applied, it is still considered isothermal, because it does not cycle back and forth between those temperatures. NASBA can be used in medical diagnostics as an alternative to PCR that is quicker and more sensitive in some circumstances.