What is undetectable?

[jmjm530]

A lot of us use the word "undetectable" when we post that we cleared the virus at this week or that. But at the same time we mean slightly different things by that term, depending on what viral load test we use.

Someone on another board posted that their doctor told them they were "undectable" with a viral load of 500. That doctor's threshold was 600. In fact, my first viral load test had that same threshold.

The Swedish study, and many others, considers <50 as "undetectable." My own doctor agrees and considers anything under 50 to be of questionable clinical value.

Regardless, I've been using Quest's Heptimax, which is a two-stage testing process that can go down to <5 IU/mg, first through conventional PCR testing, and then through TMA amplification.  So I guess when I use the term "undectable" I mean <5 IU. And I know some of you, use Labcorp's test, which I believe can go down to <2 IU.

So, in a long-winded way, LOL, here is my question: When you use the word "undetectable", what do you mean in terms of sensitivity. And if you know, what lab/test is your doctor ordering?

[artgal]

My doctor used Quest Diagnostic Lab for my 4 week viral RNA, Quantitative PCR. His words were -- "your viral load is undetectable". The HCV RNA (IU/mL) was <50 and the HCV RNA (LOG IUmL) was <1.70. This test came back after three days, which really surprised me.

[snook_man]

Mine was the quest, <5 IU/ML..
That is the only test I have had. So far, week 12 and 24 have been undetectable.

[jmjm530]

Do you know if that is Quest's qualitative test, or is it their Heptimax test which is uses both quantitative and TMA amplification? Both tests go down to <5IU/ML.

[snook_man]

Yeah, right on the lab paper it states, Heptimax (TM)..

[stc1993]

my 12 wk pcr went undetectable <600 it took only 3 days to get it back.  My 24 wk pcr was done by lab corp it went undetectable <10 it took 2 weeks to get it back.

Monte

[willing]

I had some difficulty getting my Dr. and testing clinic to use the more sensitive tests (Quest's <500 was what they were used to ordering). When I first brought it up, he gave me the sort of look I'd expect to get if I started telling a plumber what brand of wrenches to use. For most of the VL tests given in the course of tx(baseline, 24-week, 48-week, 6-month post) I don't believe there's much justification for paying the extra $ for the more sensitive tests. For example, early usage of the TMA technique as reported by <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12467774&query_hl=13">Sarazzin</a> showed that a number of patients who thought they were clear at 48-weeks turned out to actually have low-level VL and thus were bound to relapse. But if you're going to relapse VL will jump back quickly enough, so the more sensitive test isn't helping. Sensitivity does matter however, when used to mark the point in time when VL first dips below the point of visibility : you're likely to make different decisions about tx duration depending on whether your 12-week VL is 0, 25, 250 or 2500.
Comparison with studies that rely on less sensitive tests is always a problem.  I've always had a hunch that in any given study the relapse group would have shown a higher mean VL than the SVR group if a more sensitive test had been used, but since studies invariably report %s at cutoff rather than VL amounts that's hard to confirm.

I only discovered all this after my own 12-week VL test, which showed undetectable but at a <500 treshhold, which left a lot of time to wonder...

[Califia]

Yep, that's it.   A little standardization in this area certainly wouldn't hurt.

[layla]

I take undetectable as exactly that, it is on which ever test you took. If the virus is undetectable under 500, 50, 5 or 2, it is undetectable on that particular test. I would also insist on the most sensative test each time I had one. Perhaps it is not important to other people but for me it is. Eveyone is different as we all know. LL

[Dirac]

I had a limit of 615 in my tests. I was undetectable (with this number in mind) at weeks 12, 24, 48 and post treatment at weeks 12, 24 and 48. I am sure that I do not have the virus any more in my system or that is what my doctor says. So it is not the test limit but the continous and repeated "undetectable" results
Good luck

[TnHepGuy_]

Since the beginning of 2004 I've been given the Roche Taqman, with a sensitivity of <30 (quantitative) and <10 (qualitative).


As discussed by above, the lack of standardization causes all kinds of confusion in this area. And to get really nit-picky, not all of these tests are quite as accurate as others when at their lowest detection limits. <a href="http://www.projectsinknowledge.com/Init/G/1665/1665-TxReporter.pdf">Here's</a> a paper that discusses some of the tests available and their differences. (it's a PDF file)

Of course, these tests only give the doctor, patient and researcher a very partial look at things viral. Once a patient goes 'undetectable' everyone is effectively 'flying blind', since there's currently no way to determine how, when or if the virus is eliminated in the liver and associated tissues - hence the next 36 weeks of serum-clear tx for geno 1's post-week #12, the whole time with no true knowledge of if the virus is still replicating at lower levels, with relapse imminent.


TnHepGuy

[giddyup]

I'm taking infergen an riba.I'm on week 41. 2 weeks ago my test showed less than 600 on quantitive, but positive for the virus on a separate qualitive test.Bitter sweet aye. My Doctor says interpertation of the Qualitive test is difficult.she has has seen the virus detect negative in succesive tests when the patient stopped treatment.The thought is that the natural immune system keeps the virus in check.

[Califia]

I don't understand why physicians wouldn't uniformly order the most sensitive tests currently available.   Is there any rational justification for this?  (Not a rhetorical question, by the way.)

[layla]

I personally would insist on another sensative test. These more sensative test are somewhat less accurate overall. LL

[willing]

giddyup : any detectable VL at 42 weeks is discouraging, I'm sorry. As Layla suggested, testing again seems well worthwhile. Also check out the sensitivity/specificity stats for your test, usually these are above 95%.  Specificity is the fraction of cases known to have no virus which also reported  no virus on the test. So (1-specificity) would be the likelihood of your test being a false positive.

califia: yeah, it's all about $. When I checked, I believe the Quests's heptimax, at $300, was about twice the cost of its threshhold-500 test. If money's not a problem there's no reason to not always  go with the most sensitive, but otherwise it makes sense to at least do it at the 12-week point.

[giddyup]

Yup it doesn't look good.I'm hoping consensus ribba combo will pan out differently then peg at this point. Mayby as I said my Imnune system wiil keep it down.This is something my doctor thinks is Possible.I plan on finishing the study at 48 weeks.The doc said he'll put me on phase 3 protease trials when they finally come out.For now I'll just be happy to end this tx.I'm stage 4 but the old liver seems to be functioning well.Thanks for your comment.My next test is in 6 weeks.

[Califia]

The bottom line rearing its ugly head again?   Gee, what a surprise.

[LvdByGod]

i think it's just a word. and "undetectable" doesn't mean NO VIRUS. it simply means that in whatever test you had sensitive or not that if you are under it's measure mark you are no longer detectable on that test...that's all it means. i think we want it to mean more but even if it tests down to 2iu we still can't say we have no virus left at all in us.

the more sensitive test we get i guess the better our odds that we really are clear if they come out negative until the end...i guess that's the only real benefit...it's more comforting of a thought but doesn't change reality one bit unfortunately.