<43 IU/mL, but detectable - I think I finally get it

[flcyclist]

In a recent post there was a report of "Detectable <43 IU/mL".  It didn't make sense to me since I was familiar with Quest's Hepatitis C Viral RNA, Quantitative Real-Time PCR with 43 IU/mL as the lowest detection limits.  However, after reading the following from Labcorp's test, this might help to explain why it listed <43, but detectable.  

Labcorp's Hepatitis C Virus (HCV), Quantitative, RNA PCR (Nongraphical) With Reflex to Genotyping reads as follows:
- "The limit of detection of this assay is 7.1 IU/mL for HCV genotype 1, and the quantifiable range of the assay is 43 IU/mL to 69,000,000 IU/mL."  So, this test and possibly others can detect above 7.1 IU/mL and under 43 IU/mL that virus is present, but cannot quantify or count the virus under the quantifiable range of 43 IU/mL.    

https://www.labcorp.com/wps/portal/!ut/p/c0/04_SB8K8xLLM9MSSzPy8xBz9CP3I1JT8YquyzNTykNTiEqdKEOlXmpuUWqQfDlJeguBHmpoaGFga6Bfk5joCAIx2trw!/

Sorry for the hair splitting and to those that already understood, but I hope it helps some others to understand these confusing  reports.  And if I got this all wrong, please let me know.  This stuff is still so new to me.    

[drummerman2655]

My labs machine does two things .. i can give you quantitive >15  
AND it can give "HCV Not Detected IU/mL"

Which is just gave me today when I received my 9 week vl test.

AST 16     ALT 11  

I am in shock.

3 weeks to go.

dm

[flcyclist]

Billy,
I don't believe that false-positive and false-negatives are frequent since they've refined their techniques in these tests, but I think this is more of a CYA.  I don't know the %, but false results are possible.  Maybe someone has more information on the amount of false reporting on the most recent tests??

I was posting this more to show the reference range and that results ≥43 IU/mL suggest active HCV infection.

[working dog]

so what i'm getting is it could be a false positive??? so when i was 43 at end of week 4 maybe i didn't have any vl? that must be why they didn't seem like it was such a big deal at that point....billy

[flcyclist]

Maybe this test also does the same as Labcorp's - quantifies over 43 IU/mL, but can detect down to 7 IU/mL??? Is so, it doesn't indicate that on their lab test summary.  Or maybe a Qualatative test was used instead of a Quantitative in your example?  

My comments were specific to Quest's HCV RNA Quant RT-PCR.

Method:  HCV RNA Quant RT-PCR  
Real-time polymerase chain reaction (PCR)
Linear range: 43 to 69,000,000 IU/mL
Alias: HCV viral load, HCV quantitation  
Reference Range: HCV RNA <43 IU/mL

Interpretive Information:
In patients with reactive EIA results, a negative HCV RNA result typically indicates resolved infection but does not rule out carrier status; negative results may also indicate a false-positive EIA result, false-negative HCV RNA result, or intermittent viremia for a carrier.
Results ≥43 IU/mL suggest active HCV infection.

[tbd1046]

"My understanding of Quest's HCV RNA Quant RT-PCR is if detectable, it will need to be above the lower detection limits of 43 IU/mL.   If the results read < 43 IU/mL, then it is und."

Actual results have read:

"HCV RESULTS (IU) IU/mL
HCV RNA Detected, less than 43 IU/mL.            
HCV RESULT (LOG)   <1.63     Log 10"

And

"HCV RESULTS (IU)  IU/mL
HCV RNA Not detected.                            
HCV COMMENT  The lower limit of quantitation is 43 IU/mL."

My clinic accepts "Detected, less than 43 IU/ml" as detected.

[crossroadsec]

I get it now. It scares the crap out of me as I approach week 8 tho. So much is riding on this!
I just went in for a cbc differential at the local university lab so they could fax it to my hospital in OKC. I cried n hugged the nurses just talking about 4 week und.
Thanks once again for appealing to our logic. We gotta keep our wits about us while we're still fighting..
Karen :)

[flcyclist]

My understanding of Quest's HCV RNA Quant RT-PCR is if detectable, it will need to be above the lower detection limits of 43 IU/mL.   If the results read < 43 IU/mL, then it is und.  It won't report und on the results.  The Linear range of the test is: 43 to 69,000,000 IU/mL.

It you do Quest's more sensitive TMA test, Hepatitis C Viral RNA, Quantitative TMA, the lower detection limits is 5 IU/mL.  The Linear range of this test is: 5 to 7,500 IU/mL.  

This is why I was confused since Quest doesn't appear to have a test such as Labcorp's that can detect below the lower limits, but doesn't doesn't quantify the results.  If I understand correctly, Quest's tests don't report this way.  

The Heptimax test combines these two test as a rollover, so if you're interested in just doing the TMA, you can do that to save time and money.  

http://www.questdiagnostics.com/hcp/intguide/jsp/showintguidepage.jsp?fn=TS_HCV_RNA_QuantPCR.htm

http://www.questdiagnostics.com/hcp/intguide/jsp/showintguidepage.jsp?fn=TS_HCV_RNA_QuantTMA.htm

http://www.questdiagnostics.com/hcp/intguide/jsp/showintguidepage.jsp?fn=TS_Heptimax.htm

[lynda607]

Sorry his3707, you were inquiring about the Quest RT PCR.  I did not see the "quest" until after I had posted the above.

[lynda607]

The test will read either:

<43 HCV RNA DETECTED
                 or
<43 HCV RNA NOT DETECTED

This is with the LabCorp Hepatitis C Virus (HCV), Quantitative, Real-time PCR

If HCV RNA detected at 43 IU/mL or above the test will give the numeric value.  

[his3707]

does anyone have an example of what a test result for the quests HCV RNA Quant RT PCR <43 looks like for detectable or undetectable <43 looks like. also for the lab corp test you are talking about here?  Thanks  Lydia

[flcyclist]

After reading the Labcorp test, for some reason it suddenly became very clear.  I reread your response in dixiechic's thread and it says essentially the same thing, but I guess my mind wasn't digesting quickly enough.  Thanks for your help in clarifying.  

I just didn't want to hijack dixie's great news with this technical stuff.

[lynda607]

Regarding the Labcorp test flcyclist is talking about:

The limit of quantitation on that test is 43 IU/mL or above.  If HCV RNA is deteced the test can give a numeric number (viral load) if the IU/mL is 43 or above.  The level of dectection goes down to 7.1 IU/mL.  The assay will detect HCV RNA down to 7.1 IU/mL which is fairly sensitive but it can't quantify or give a numeric value for any HCV RNA detected between 7.1 IU/mL and 42 IU/mL.  The patient is still detected, but no numeric value can be assigned.  
HCV RNA detected but under the quatifiable range should not be considered undetected.  This is particually important for patients treating with Incivek at the 4 week mark.

[working dog]

mine was 43 at 4 weeks...they said it was almost none...i still don't get it all the way...i have to wonder how long they'll want me to tx...in 2 weeks i'll know my 8 week and would like to think i'll be undetectable.....thanks for looking into this......billy

[ninjamonkey]

I'm confused

[willbb]

Sometimes takes a while...:0        good tho you guys are interested enough to keep at it

Heck...I still don"t know how to use my  black berry and been trying for 4 years  :)

[hrsepwrguy]

Your not alone, I didn't get it either, lynda almost had to smack over the head before I understood.