Viral load tests PCR VS. Bdna

[JCB1606]

The numbers between the PCR test and Bdna test results are different.The PCR detects a lower limit .Is the bdna test as dependable as the PCR? If the bdna test rests are UDT is that comparable to the PCR UDT test results for accuracy?  I've been recieving the bdna test and UDT @ 4,12 and 24 weeks. Am I really UDT? Thanks

[Bali05]

That makes perfect sense.
Problem is a very reputable Dr. I consulted told me the
38K value could show higher with a more sensitive test which he wanted to run right
away but I prefer to stay with the same for now to compare apples to apples.
Should the <615 test come back UND a more sensitive test will be at order.

Thanks for clarifying this.

Bali05

[GoofyDad]

I think if you ran the same blood through the same test - your'd get somewhat diferent results - the amplification process isn't perfect. But that's not the point (or the question). In theory any test should have given about the same results. The situation when a more sensitive test make a diference is when you're blow the level of sensitivity of the higher test.

Say you were at 500 - then the < 615 test would have shown you as UND. The <50 test would have shown you as 500. Where you are now - any test should show you at about 38,000.  

[Bali05]

Bill,

The test was done by BioReference Labs here in the US.

GoofyDad,

I understand the test only goes to <615 .

If I would have tested same blood with a test <50 would that test

being that is more more sensitive also increase the 38,466 value

and if so of up to how much can that differ ?

[GoofyDad]

To be clear on this for the sake of others who have asked: The < 615 and < 3200 are there to show the "normal" result for a healthy person. This test goes down to 615 IU so a normal result for this test is < 615. This test can't distinguish between 0 and 614, it can only say < 615 or an actual number that is 615 or higher.

< 615 is expected result

38, 466 is actual result.

[Bill1954]

Sorry to hear about your mother’s cancer; you have my condolences. Yes, I would use that way of expressing it; 38,466 IU/mL. Just out of curiosity, was the result quoted in copies/mL generated here in the U.S., or was it an overseas result?

Bill

[Bali05]

Bill,
I went to battle for 2 years fighting my mothers pancreatic cancer. Believe me
I know about the importance of getting things in writing

On this forum many people quote their VL. If someone asks me for my viral load

the aswer is : 38,466  correct ?

[Bill1954]

Bali—

“If someone asks me for VL what do I aswer please ?”

Most labs use IU/mL now; it would benefit you to answer in IU/mL. It sounds as if someone quoted you a number using copies/mL at one time? This underscores the importance of getting everything in writing, and spending the time to ascertain their methods.

To simplify this, ask for copies of your labs, and make sure they are using IU/mL in the future. There are conversion tables available, but it gets difficult, because different labs used different values in transcribing copies to IU:

http://janis7hepc.com/Viral_Loads.htm

Assay Conversion Factor

Amplicor HCV Monitor v2.0
(manual procedure) 1 IU/mL = 0.9 copies/ml
Cobas Amplicor HCV Monitor v2.0
(semi-automated procedure) 1 IU/mL = 2.7 copies/ml
Versant HCV RNA 3.0 Quantitative Assay 1 IU/mL = 5.2 copies/ml
LCx HCV RNA Quantitatiive Assay 1 IU/mL = 3.8 copies/ml
SuperQuant 1 IU/mL = 3.4 copies/ml


Best to you—

Bill

[Bali05]

Hi GoofDad,

The above is my VL from 6.12.09.

First they told me it was 2 Million. Than I got home all depressed looked at the number and saw that they did not read the comma right. So they corrected
it 200,024. After that I spoke to someone else who told me the I.U. value
is your real VL.I spoke to doctors who told me this was high and to doctors
who say it is low and to doctors who say it is low but could be higher with a different
test !!??
If someone asks me for VL what do I aswer please ?

[GoofyDad]

Bali -

I'm not Bill, but I once played him on TV. The swooning females were amazing. OK - overwhelming at times. Just kidding.

Since you are currently detectable above the lower limit of the bDNA test - this turned out to be a perfect test for you at this time. The two readings you show are the same thing - one stated in individual copies (virons) and the other in International Units. The International Units has some sort of a standardizing mechanism built in to make it easy to compare different tests run on different machines. In any case, your viral load is quite low - but still beyond being undetectable.

You are close enough to UND that it would make sense to go for a test with a greater degree of sensitivity on your next round of testing.  

  

[Bali05]

Bill,

kind of lost you there with all that log stuff

Hep.C,RNA,bDNA,QNT~      200,024       <3200 copies/ml
Hep.C,RNA,bDNA,QNT~        38,466        <  615  I.U./ml


What is your first impression by looking at these numbers ?

How much different could this be with the PCR <50 I.U./ml test ?

[GoofyDad]

bDNA give true UND to the level of it's sensitivity. And it's not that sensitive. Thus, it's probably not the best choice for assessing UND on tx. Once you are off the viral suppression drugs, it seems unlikley that you would be able to maintain a non-zero viral  load that was below the bDNA sensitivity. If a viable virus was present, one could expect it to rapidly climb above the level of detectability.    

[JCB1606]

The results you posted  for the Bdna assay ,<3200 and <615 are the same VL results I have been getting from the the VA @4,12,24 weeks and 4 months post TX. Do these results give a true answer for UDT?  Thanks for the detailed answers.

[Bill1954]

Goof-

Thanks; as usual, you’re correct. I had to look up the old hard copies of the CPMC testing and we received the same testing; bDNA QUANT, TMA QUAL. I don’t know why I keep crossing my wires on this—

Bill



Bali05—

I hope the info I’m offering is correct; I’m just another schmuk on this forum trying to understand this subject along with everyone else :o).

“if you were to run the different VL test types
from the same blood does one end up
with different VLs?
How by much can they be different ?”

I believe the answer to this would be yes; the qualitative results would probably differ. I understand that nucleic acid testing is only sensitive to + or - .5 log, so it can vary by up to one log. This is a very large numerical number when the viral load is in the millions, but is much more accurate as the load is reduced. For instance, if the actual numerical load is say, 20; the log value is 1.30. If the test is accurate to .5 log, this would mean a very small discrepancy in low numbers; in this case, it would be accurate to log .65.

“Is it true that these tests count viral material and do not differentiate between live or dead Virus?”

I don’t know. I believe NAC testing relies on “lighting up” or fluorescing the virus, then using a meter to gauge the degree of fluorescence, and by that, determining the actual quantitative load. Whether this assays for all viral particles, or only active, viable virus is a question for another guy :o). Good question, though.

Bill

[Bali05]

Bill,

if you were to run the different VL test types
from the same blood does one end up
with different VLs?
How by much can they be different ?
Is it true that these tests count viral material and do not differentiate between live or dead Virus?

[GoofyDad]

Like Oprah after a rack of ribs, I'm gonna bust your chops again on qualitative vs quantitative. When I treated at CPMC they ordered bDNA for vial count (quantitative) and TMA for detectable/non-detectable (qualitative).

At least I think I have that right.

  

[Bill1954]

Hi Bali—

The bDNA viral assay isn’t used as much by clinicians anymore in favor of more sensitive methodology. There are essentially three types of viral testing available for HCV

bDNA
PCR
TMA

While bDNA is very *specific* for disease (that is when it says you have disease, it means it), it is less sensitive, as evidenced by it’s lower limit of sensitivity (<615 IU/mL).

Clinicians are more inclined to order either the PCR (Polymerase Chain Reaction) or TMA (Transcription Mediated Amplification) due to their superior dynamics. The PCR test typically has a lower dynamic range of <50 IU/mL, and TMA tests to <5 and in one instance that I’m aware of to  <2 IU/mL.

International units have been used to express viral load now for several years; other expressions that were formerly used were copies/mL, as well as EQ/mL. Most labs now utilize the new IU format, but it’s a good idea to make sure if you’re looking at old studies that might have utilized other methods.

Bill

[Bali05]

Hi Bill,

You sound like you know a lot about the different VL tests.

Any idea what kind of test this is and how it compares to other tests ?
Also when referring to ones viral load the I.U./ml value would be the one ?

Hep.C,RNA,bDNA,QNT~            <3200 copies/ml
Hep.C,RNA,bDNA,QNT~            <  615  I.U./ml


Thank you
Bali05

[Bill1954]

The way you have phrased your question makes it difficult to answer. Yes, typically, a PCR test has a lower limit of sensitivity; if that is what you are looking for. If you are looking for specificity, the bDNA test is superior.

My hepatologist would order both tests for viral assay; the PCR quantitative (actually TMA) for purposes of sensitivity, and bDNA qualitative for specificity.

Most clinicians now use either a PCR quantitative test which typically has a lower limit of sensitivity of <50 IU/mL, or a TMA qualitative for sensitivity to as low as 2 IU/mL.

A good test for early treatment is Quest diagnostic’s ‘Heptimax’; this is a two part test that utilizes both PCR and TMA methodology. If the sample being tested is <50 IU/mL, then the sample is tested again with TMA technology; this lowers the limit to <5 IU/mL.

Bill