If it were me, I'd test again at week 12 per normal protocol. That would be the day before your 13th shot. A good test to ask for would be "Heptimax" by Quest Diagnostics. It is very sensitive and goes down to 5 IU/ml. In fact, any further tests should be senstive tests like Heptimax. It's not unusual that the doctor gave you the test he did. Just not the best test IMO. And certainly the wrong test from here on out since you are below its limit. But as Mike said, not to worry. Chances are that you will also be non-detectible with the more sensitive test.
Be well.
-- Jim
Alternatively, you could ask them to run a more sensitive PCR or TMA on the same blood, assuming the lab still has enough left. If you go this route, make sure whatever test they run has a sensitivity of at least 50 IU/ml and preferably 10 IU/ml or under.
Good suggestion Jim. When I scheduled to have next week's PCR drawn, I checked around to find out what test would be used and it's sensitivity before I made the appointment.
I would have prefered the <5 but settled for the <50 at this point as all I need to show, according to the statement at my last follow-up, is a 2 log drop over the 12 wks of 1400 mg of riba from my original baseline of 72,000,000 last January. I figured UND <50 certainly is more than the 720,000 required for the 2 log drop, and if it is UND, then I can pursue a <5 test for a more precise measurement.
Another good <2/<5 test(depending if you're talking copies or I.U.) is the 'Quantasure' from LabCorp.
As I understand it, bDNA is the most accurate at measuring what your viral load is, if you have a viral load, and it is higher than 615.
TMA is the most sensitive at detecting the absence/presesence of virus, but is doesn't measure what it finds.
If you expect to find virus (like at baseline) bDNA is a good choice. If you expect you may be UND, TMA is a good choice. My doc will usually tag a bDNA onto the TMA even when UND is expected, presumeably as a redundancy. I prefer TMA over PCR because I've read a number of published studies on it's accuracy. Sensitive PCR may be just as good though. Google 'tma residual viremia'.
As Jim says, Heptimax is another good way to go.
A PCR <50 is considered sensitive and should be fine. In fact, as of the last time I checked, that was the most sensitive test used in the European trials -- in other words <50 was considered non-detectible for all practical purposes.
That said, what lab are you using? If it's Quest, you can have the PCR reflexed (automatically re-tested) to a qualitative or quantitative TMA if the PCR shows <50. That way you only have to get stuck once :)
Good luck and be well.
-- Jim