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Taqman Clarification
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Taqman Clarification

I'm freaking a little bit.  For the life of me, I cannot understand the difference in these results.  Prob because it's my daughter, I'm too high-strung emotionally to see.  But her doc says she was detectible at week 4, so I had to fight to get the additional PCR at week 6.  And that one ends by saying Not Detected.  To me they both look pretty much the same except for the UND/DET thing.  Please take a look and let me know what you think. Thanks so much.

4 week results:

HCV RT-PCR, Quant (non-graph)

Hepatitis C Quantitation                                 will follow

HCV RNA was detectable but not quantifiable.  Additional more sensitive testing is being performed.

HCV log10
Unable to calculate result since non-numeric result obtained for component test.

Test Information:
the quantitaive range for this assay is 25 IU/ml to 69 million IU/ml using a combination of Taqman real-time PCR (LLOG 43/IU/ml) plus reflex to another Taqman assay (LLOQ25 IU/ml) for low viral load samples that were detectable by the original Taqman real-time PCR assay but not quantifiable. The limit of detection of the assay is 7.1 IU/ml for HCV genotype 1.



Week 6:

Hepatitis C Quantitation

HCV RNA detected
HCV RNA was detectable but not quantifiable. Additional more sensitive testing is being performed

HCV Quant II
HCV RNA was detectable at low levels.  Additional reflex testing was attempted, quantitation was not possible

HCV log10
Unable to calculate result since non-numeric result obtained for component test

HCV log10
Unable to calculate result since non-numeric result obtained for component test

Test Information:
the quantitaive range for this assay is 25 IU/ml to 69 million IU/ml using a combination of Taqman real-time PCR (LLOG 43/IU/ml) plus reflex to another Taqman assay (LLOQ25 IU/ml) for low viral load samples that were detectable by the original Taqman real-time PCR assay but not quantifiable. The limit of detection of the assay is 7.1 IU/ml for HCV genotype 1.

Hepatitis C RNA-PCR Negative           HCV RNA not detected

COMMENT:  This patient's speciman is NEGATIVE for Hepatitis C virus RNA by the PCR amplification method and DNA Probe Detection.  Negative results do NOT rule out the possibility of HCV infection.  PCR results should vbe used in conjunction with othe laboratory test results and the patient's clinical profile.  






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15 Comments Post a Comment
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419309_tn?1326506891
It's so hard to think straight when our emotions are all tied up in knots... big hug to you, Izzy.

What it seems to boil down to is that your daughter's first test at 4 weeks revealed a VL somewhere between 25IU/ml and 43IU/ml:  detectable at greater than 25IU/ml but the assay doesn't quantitate between those values.

The second test at 6 weeks was considered not detectable because your daughter's doctor is viewing the lower limit of 25IU/ml as the line of distinction between det/und.  Your daughter's second result showed virus somewhere between 7IU and 25IU per ml, but again, the assay does not quantify between 7IU and 25IU.

Hope that helps Izzy... best wishes for SVR to your daughter.

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1669790_tn?1333666195
I understand the Week 4 PCR results, but the Week 6 appear to have contraditing statements.  I'm confused by this report.  I'd ask your doctor to explain:

HCV RNA was detectable, but not quantifiable.
HCV Quant II; HCV RNA was detectable at low levels.
then
Hepatitis C RNA-PCR Negative, HCV RNA not detected

Very confusing way to report.  Hope it works out as indicated

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1669790_tn?1333666195
It's also hard to think straight when on these meds, lol.  I'm still confused, nothing new.

6 Week PCR states:
"Taqman assay (LLOQ25 IU/ml) for low viral load samples that were detectable by the original Taqman real-time PCR assay but not quantifiable. The limit of detection of the assay is 7.1 IU/ml for HCV genotype 1."

Since the report state "Negative" and Not Detected, wouldn't the VL need to be below the limit of detection (7.1 IU/ml)?  
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419309_tn?1326506891
"the quantitaive range for this assay is 25 IU/ml to 69 million IU/ml using a combination of Taqman real-time PCR (LLOG 43/IU/ml) plus reflex to another Taqman assay (LLOQ25 IU/ml) for low viral load samples that were detectable by the original Taqman real-time PCR assay but not quantifiable. The limit of detection of the assay is 7.1 IU/ml for HCV genotype 1."

"The quantitative rage for this assay is 25 to 69 million"... so it can only quantify VLs above 25.  The particular assay will read undetectable, as that is the range of the original Taqman.
The limit of detection is down to 7.1, but that is not this particular Taqman test's deteremination of 'detectable'... it will only say detectable if the VL is 25 or higher.
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1669790_tn?1333666195
I thought detectable if VL from 7.1 - 25 IU/ml, but quantifiable if VL > 25 IU/ml ???

I'm still confused, need sleep, g'night :o)  
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419309_tn?1326506891
Guess I'm not explaining it very well... one more try.

The result is such because the report is the result of 'reflex' testing.  
(1) They use a test that can quantify 43IU or higher with a detection rate down to 7.1.  This test was detectable, but it's not the final report of the test, only the process.
(2) because the above was positive, they run the reflex that has a quantitative range and lower limit of detection of 25IU, and it was negative
In this particular Taqman, Quant II represents the end result.  In order for process/part one to also be negative, VL would have to be 7IU or lower.
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1669790_tn?1333666195
Yes, I understood this to be a two part test, similar to the Quest's Heptimax, RT-PCR and TMA tests, with similar limits of detections, but different lower limits of quantification.  

If the limit of detection of both of these tests used is 7.1 IU/ml, then how can one test show positive and the more sensitive test show negative?  This is what I don't understand.

I guess what you're saying is, regardless of what the first test shows, the Quant II (reflex) is the definative test and final test, and did not show a VL > 7.1 IU/ml.  I wish they gave a better explanation on the test.

Eureka, thanks for your insight on this explanation.  Notice I didn't say incite this time.  ;o)

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419309_tn?1326506891
"If the limit of detection of both of these tests used is 7.1"
-------------
That's probably what's causing the confusion: Part I quantification has a lower limit of 7.1, but part 2 quantification only has a lower limit of 25 IU, not 7.1
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412873_tn?1329178055
~Hepatitis C RNA-PCR Negative           HCV RNA not detected~

I thank you both for your input.  Taqman is still so confusing to me.  Based on the comment above...I believe she was UND somewhere between week 4 and 6?  

Wish it was more simple...like the Quest Heptimax...I may be going old school....but at least it was clear.  

Thanks so much,

Isobella

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Avatar_f_tn
I hate to say this, but it looks inconclusive to me. It looks like they are indicating that there might be some virus left. Since it is an amount right on the borderline of detection they cannot commit to a definitive answer. The only thing that will clear it up is the next test.

When is the next VL test? I would consult with the doctor at that point taking into consideration her genotype, IL28B type and all the other health factors.

I don't know your daughter's genotype but I was interested to find out recently that there are rare cases of under quantitation in GT4 specimens because the test probes do not cover all mutations of the viral genome. I have always wondered about people being apparently undetected for long periods then relapsing. One answer is that the virus is lurking dormant in cells which have a very long lifecycle. Another answer is that VL tests cease to detect a mutant version of the virus whihc develops when the natural replication pathways are blocked. When treatment stops, the virus then has a chance to revert to it's natural form when it can be detected once more.

Either way, I would do more testing and play it safe - whatever that means in your daughter's case. She's lucky to have a Mum like you on her side.



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979080_tn?1323437239
While on tx I  used the LabCorp NGI Quantasure  <2 IU.
It is the most sensitive  Quant. available.
I used to be geno 4a,c.

b
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412873_tn?1329178055
~~Hepatitis C RNA-PCR Negative           HCV RNA not detected

COMMENT:  This patient's speciman is NEGATIVE for Hepatitis C virus RNA by the PCR amplification method and DNA Probe Detection.  Negative results do NOT rule out the possibility of HCV infection.  PCR results should vbe used in conjunction with othe laboratory test results and the patient's clinical profile~~

I'm thinking that meant UND at week 6.  Her doctor speaks in circles.  Trying to give false hope while delivering the news of 48 vs 24.  I'm kicking myself for not getting better testing (meaning testing I can understand, perhaps). And not getting it done at 5 weeks.  Never even thought about the LapCorp NGI Quantisure.  

I know the protocol, I know the gray areas, but it's my kid for crying out loud.....I don't want her to have to do 48.

For the record, we were  geno 1a, CT.  

Thanks so much for your input.  It helps me keep perspective.

Sincerely,

Isobella

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Avatar_m_tn
Hi there, you are and have been in a position that no parent wants to be in. I can understand you not wanting your child to do 48 weeks, yet you also want her to have the best possible chance of being rid of this forever. So no need to rehash what is recommended. It seems quite clear at 4 weeks she was still detected by the standards...... This is form the mayo clinic on being detected and being und concerning tx. Wishing you both the very best.

A "Detected" result with the comment "HCV RNA level is <43 IU/mL (<1.63 log IU/mL). This assay cannot accurately quantify HCV RNA below this level." indicates that the HCV RNA level is below the lower limit of quantification for this assay. When clinically indicated, follow-up testing by this assay is recommended in 1 to 2 months. For the purposes of assessing response-guided therapy eligibility, an "Undetected" result is required; a "Detected" result below the limit of quantification should not be considered equivalent to an "Undetected" result.

http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/83142
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419309_tn?1326506891
Too many choices and all that technical jargon really just makes things more confusing; imho <2 is overkill and <45 is insufficient.  It's important to keep in mind that all the current protocols are based on data accumulated on the DAAs during research using 25 IU/ml as the lower limit of quantification, so that's the cut-off to use when using VL to gauge treatment response and time lines.  Can-do is right, she was not undetected at week 4 -- but the expectation is that since she was at week 6, she should be at 8 and 12 as well... hang in there Izzy.
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412873_tn?1329178055
Thanks so much for helping me find balance.  I know (now) that I'm grasping at straws thinking the 4 week was the same as the 6.  

She's actually doing really well.  Once triple therapy and the need for 20 grams of fat is out of the equation, I'm thinking she's gonna find tx way easier.

I'm countng my blessings-at the top of the list is everyone here!!

All the best,

Isobella

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