Hi Doc,

I understand Brian Conway's team (University of British Columbia) picked up an atypical case of HIV by sending a plasma sample for resistance test, even though the patient had negative ELISAs 12 and 14 months after exposure, negative bDNA, negative DNA PCR and a negative co-culture with PBMCs. See http://www.thebody.com/Forums/AIDS/SideEffects/Archive/Testing/Q156332.html. Brian Conway,M.D. explains that as part of this process, the resistance test sequences the virus using a technique that is quite different from Roche PCR and bDNA.

My very basic understanding is that PCR technology is used in the viral load assay and the genotypic resistance test. However the resistance test then requires further technology to determine the DNA sequence of the PCR product that was generated.

I would be FOREVER GRATEFUL if you would advise me how precisely/else the resistance test is different from Roche PCR and bDNA.

This is too complex of a question to answer here. You are correct that PCR is used in the first step of the genotyping resistance assay followed by a sequencing reaction to determine the DNA sequence that uses different biochemical steps. PCR is not used for the bDNA assay.