You could discuss either of these HCV RNA tests; they are both extremely sensitive, and either would be appropriate for in-treatment testing:
Labcorp’s NGI Quantasure # LC 140639
I believe this is an HCV Quantitative test with a <2 IUmL lower limit of sensitivity. Labpcorp has other HCV tests with similar names; be sure to request the exact number above. Additionally, this test was unavailable recently for a period of time; be sure it is currently available.
Quest diagnostic’s ‘HEPTIMAX’, with a lower limit of sensitivity of 5 IU/mL:
http://www.questdiagnostics.com/hcp/topics/heptimax/heptimax.html
As far as the ‘why’ is concerned, please review this post from the Medhelp archives that discuss this in depth:
http://www.medhelp.org/posts/Hepatitis-C/Lab-Corp-no-longer-offering-10-PCR/show/772286
Good luck—
Bill