Aa
HR, Jim, mremeet, Goofy Dad, anyone that has knowledge of pcr testing?
Hi everyone,
Some of you have been following the saga of my "29" at week 12 as well as APK's. I do think/hope my 29 at week 12 is an "artifact" or false positive but for my own peace of mine, I want to comfirm that by getting the most sensitive and accurate pcr test available. Asked my doctor about it yesterday and the study can't provide one more sensitive than the one we've all been discussing but he told me I was welcome to get one on my own.
There's a lot of confusion in my mind surrounding these tests. Searched the archives and found something Goofy Dad posted in Nov.06
http://www.natap.org/2005/HCV/122805_04.htm
Conclusions: Among patients treated with combination therapy for chronic hepatitis C, the TMA test detects HCV RNA in all specimens that are Amplicor-positive, as well as an additional 21.6% that are Amplicor-negative. The increased sensitivity of the TMA test can be helpful in identifying patients with low levels of HCV RNA who are likely to relapse when therapy is stopped. Furthermore, among patients with EVR and a negative Amplicor test at W20, persistent detection of HCV with the TMA test during therapy predicts failure to achieve SVR.
*FDA-approved for detection of HCV RNA as evidence of active infection.
Can someone explain to me like I'm five years old what the above means. Also, HR posted on 11/12/06 the following:
(Continued below)
Some of you have been following the saga of my "29" at week 12 as well as APK's. I do think/hope my 29 at week 12 is an "artifact" or false positive but for my own peace of mine, I want to comfirm that by getting the most sensitive and accurate pcr test available. Asked my doctor about it yesterday and the study can't provide one more sensitive than the one we've all been discussing but he told me I was welcome to get one on my own.
There's a lot of confusion in my mind surrounding these tests. Searched the archives and found something Goofy Dad posted in Nov.06
http://www.natap.org/2005/HCV/122805_04.htm
Conclusions: Among patients treated with combination therapy for chronic hepatitis C, the TMA test detects HCV RNA in all specimens that are Amplicor-positive, as well as an additional 21.6% that are Amplicor-negative. The increased sensitivity of the TMA test can be helpful in identifying patients with low levels of HCV RNA who are likely to relapse when therapy is stopped. Furthermore, among patients with EVR and a negative Amplicor test at W20, persistent detection of HCV with the TMA test during therapy predicts failure to achieve SVR.
*FDA-approved for detection of HCV RNA as evidence of active infection.
Can someone explain to me like I'm five years old what the above means. Also, HR posted on 11/12/06 the following:
(Continued below)
MEDICAL PROFESSIONAL
First ; TMA = Transcription Mediated Amplification, an in vitro amplification method of small stretches of RNA that uses RNA Transcription rounds for its amplification cycles.
PCR = Polymerase chain reaction. It uses up to 55 rounds ( cycles) of a molecular biology reaction that starts with a small specific stretch of DNA e.g. 100 bases long that are part of the viral genome and duplicates that starting material in each round again and again so that in the end a relatively gigantic amount of that specific stretch the " amplicon" is made, still "proportional" to the starting amount, so by quantitating the end product so can quantitate the starting amount = the virus by comparison with a standard that you have equally amplified.
With HCV , a RNA virus, the RNA is first reverse transcribed into DNA, then PCR is used.
A qualitative test is nothing more than a TMA or PCR where:
1. a much larger amount of serum (starting material to investigate) is being prepared and
2. then the amplification process is driven to the extreme, to detect any copy of a virus present in the starting material. This way you obtain highest sensitivity, but you loose quantitation above the detection limit, because you literally "overamplify". Often even a single copy of the virus in the starting material of 1ml of serum will be detected.
Everything has to be optimized to achieve this result. This is called " Robust single copy PCR".
Sometimes HCV is so intensely lipidated, that the ultracentrifugation step used to pellet it down from the starting serum, despite lowering specific gravity of the serum,cannot cath this virion - it floats, because it contains too much fat. Thats why the sensitivity limit is "officially" 2 iU = 5 copies(virions)/ml.
In quantitative PCR we simply use much less starting material and less and less cycles to obtain amplification strength that allows quantitation in the desired range.
PCR = Polymerase chain reaction. It uses up to 55 rounds ( cycles) of a molecular biology reaction that starts with a small specific stretch of DNA e.g. 100 bases long that are part of the viral genome and duplicates that starting material in each round again and again so that in the end a relatively gigantic amount of that specific stretch the " amplicon" is made, still "proportional" to the starting amount, so by quantitating the end product so can quantitate the starting amount = the virus by comparison with a standard that you have equally amplified.
With HCV , a RNA virus, the RNA is first reverse transcribed into DNA, then PCR is used.
A qualitative test is nothing more than a TMA or PCR where:
1. a much larger amount of serum (starting material to investigate) is being prepared and
2. then the amplification process is driven to the extreme, to detect any copy of a virus present in the starting material. This way you obtain highest sensitivity, but you loose quantitation above the detection limit, because you literally "overamplify". Often even a single copy of the virus in the starting material of 1ml of serum will be detected.
Everything has to be optimized to achieve this result. This is called " Robust single copy PCR".
Sometimes HCV is so intensely lipidated, that the ultracentrifugation step used to pellet it down from the starting serum, despite lowering specific gravity of the serum,cannot cath this virion - it floats, because it contains too much fat. Thats why the sensitivity limit is "officially" 2 iU = 5 copies(virions)/ml.
In quantitative PCR we simply use much less starting material and less and less cycles to obtain amplification strength that allows quantitation in the desired range.
He may not admit that you're right to your face, doctors have pride and ego like anyone else. But inside he'll know you're right, and much more importantly he'll probably incorporate what he learned from you into his future practice - hopefully for the benefit of all his patients.
Agreed mrmreet. I guess somewhere deep inside of me I just want to be right and "win" this one with the doc (and for my H's future well being) so I'm looking for intelligent support for my argument! I'd pretty much convinced myself I was right and was thinking I'd write up the lab slip as such. The tenatious pig headed part of me wants the "young whipper snapper doc" to concede and he just won't bite!
If your doctor is receptive to discussing the possible benefit of testing at the lowest level possible, then I'd simply print out the studies referenced above by PDS and HR and then hand them to your doctor on your next visit. Use a highlighter to mark off the most salient statements, including:
"Among patients treated with combination therapy for chronic hepatitis C, the TMA (5-10 IU/ml) test detects HCV RNA in all specimens that are Amplicor-positive (50-100 IU/ml), as well as an additional 21.6% that are Amplicor-negative. The increased sensitivity of the TMA test can be helpful in identifying patients with low levels of HCV RNA who are likely to relapse when therapy is stopped. Furthermore, among patients with EVR and a negative Amplicor test at W20, persistent detection of HCV with the TMA test during therapy predicts failure to achieve SVR."
The benefit of a more sensitive test as described in this study seems pretty straightforward and common sensical. Hopefully your doctor will agree. And if he does you'll not only be helping yourself, but you'll be helping his future (and current) patients by bringing it to his attention as well. But even if he doesn't see the light, sounds like he won't object to you getting the more sensitive test anyway.
"Among patients treated with combination therapy for chronic hepatitis C, the TMA (5-10 IU/ml) test detects HCV RNA in all specimens that are Amplicor-positive (50-100 IU/ml), as well as an additional 21.6% that are Amplicor-negative. The increased sensitivity of the TMA test can be helpful in identifying patients with low levels of HCV RNA who are likely to relapse when therapy is stopped. Furthermore, among patients with EVR and a negative Amplicor test at W20, persistent detection of HCV with the TMA test during therapy predicts failure to achieve SVR."
The benefit of a more sensitive test as described in this study seems pretty straightforward and common sensical. Hopefully your doctor will agree. And if he does you'll not only be helping yourself, but you'll be helping his future (and current) patients by bringing it to his attention as well. But even if he doesn't see the light, sounds like he won't object to you getting the more sensitive test anyway.
I have read this thread and will try to explain the kenetics of the viral decay and how it will relate to the PCR testing and sensitivities. Then hopefully somebody like hepatitisresearcher can chime in and tell me if this is right.
It seems that there are 2 main slopes to viral reduction which are the following:
1-Initial quick drop in the first 24 hours of TX, this is due mostly to the initial kill of the virus directly and is due to the interferon mostly. Usually a 1 to 1.5 log reduction.
2-The next stage of viral reduction is usually represented by a logrithmic decay of the viral load and is typically linear along the log graph. This slope along with how long you treat will ultimately determine your chances of success. I think the slope of this line is due to your body's ability to kill the infected hypocrites (sp) and this can range from individual to individual.
Now to the good stuff:
To get a sustain response you need to drop you viral count to nearly zero. NOT YOUR BLOOD tests which only measure a mere fraction of the the amount of plasma in your body, but you whole body.
The amount of virus detected in your PCR represents a small fraction (1/10,000) of the viral copies in your total body. So say you have 9 copies (which is undetectable with a very sensitive test) you could have approx. 9 X 10,000 or 90,000 copies of virus in your system. That 90,000 needs to get pretty close to zero to get a sustained response. You need another 4 to 5 log drop of viral load to be clear.
So hypothetically speaking, the sensitivity of a PCR test to actually tell you if you are clear of the virus would in theory be 0.00001 IU/ml.
So when we speak of a test that goes to 5, 10, 30, or even 50, all these tests are relatively the same number because they are within one log of each other.
So to recap, somebody with a starting viral load of 1,000,000 would need an 11 log reduction to clear the virus. A (10 iu/ml)test would only measure a 5 log reduction, And a (50 iu/ml) test would only measure approx. a 4.75 log reduction. On a log scale these numbers are virtually the same.
Any thoughts?
I am also going 72 weeks.
It seems that there are 2 main slopes to viral reduction which are the following:
1-Initial quick drop in the first 24 hours of TX, this is due mostly to the initial kill of the virus directly and is due to the interferon mostly. Usually a 1 to 1.5 log reduction.
2-The next stage of viral reduction is usually represented by a logrithmic decay of the viral load and is typically linear along the log graph. This slope along with how long you treat will ultimately determine your chances of success. I think the slope of this line is due to your body's ability to kill the infected hypocrites (sp) and this can range from individual to individual.
Now to the good stuff:
To get a sustain response you need to drop you viral count to nearly zero. NOT YOUR BLOOD tests which only measure a mere fraction of the the amount of plasma in your body, but you whole body.
The amount of virus detected in your PCR represents a small fraction (1/10,000) of the viral copies in your total body. So say you have 9 copies (which is undetectable with a very sensitive test) you could have approx. 9 X 10,000 or 90,000 copies of virus in your system. That 90,000 needs to get pretty close to zero to get a sustained response. You need another 4 to 5 log drop of viral load to be clear.
So hypothetically speaking, the sensitivity of a PCR test to actually tell you if you are clear of the virus would in theory be 0.00001 IU/ml.
So when we speak of a test that goes to 5, 10, 30, or even 50, all these tests are relatively the same number because they are within one log of each other.
So to recap, somebody with a starting viral load of 1,000,000 would need an 11 log reduction to clear the virus. A (10 iu/ml)test would only measure a 5 log reduction, And a (50 iu/ml) test would only measure approx. a 4.75 log reduction. On a log scale these numbers are virtually the same.
Any thoughts?
I am also going 72 weeks.
Thanks for the info. I'm going to look for that Chicago paper. An old beau of mine is a former NIH/Johns Hopkins HIV/HCV co-infectious disease specialist and I was sorely tempted to make contact after 20+ years to get some definitive answer to this testing question as it seems to be a sticking point with many of the mainstream docs. I made a similar argument with the doc based on what I've learned here. I'm considered an intelligent person ('though not a medicine "doc") and the doc conceded that the rationale/argument was sound, but felt simply that there was no substantive information to worry about searching for a more sensitive test. He simply deferred to whatever I felt "we" should do. I'll add Heptimax to my H's lab and have him go to Quest lab (doc gave me his entire year's worth of lab slips and just calls me and tells me what he wants to run so the reality is I can write/X anything I want). I'll sleep alot better if I feel that UND really is UND, right now I'm not convinced but I don't say a word to my H as he's feeling on top of the world (which in some respects he is at 13,000 ft. w/skis strapped to his feet right now). I am continually impressed by the depth of knowledge and conversation on this forum. I'm grateful to have stumbled on it. I'm also cheered by the fact that our family doc grills me every four months when I'm in to see him about this disease. I think he's feeling a tad guilty for not discovering this in my husband when his liver enzymes rose in 1988 and rose again in 1998. If only I knew then what I know now... sigh.....hopefully the family doc will be a smarter family doc.
Have an Answer?
You are reading content posted in the Hepatitis C Community
Learn about this treatable virus.
Getting tested for this viral infection.
3 key steps to getting on treatment.
4 steps to getting on therapy.
What you need to know about Hep C drugs.
How the drugs might affect you.
These tips may up your chances of a cure.
A list of national and international resources and hotlines to help connect you to needed health and medical services.
Herpes sores blister, then burst, scab and heal.
Herpes spreads by oral, vaginal and anal sex.
STIs are the most common cause of genital sores.
Condoms are the most effective way to prevent HIV and STDs.
PrEP is used by people with high risk to prevent HIV infection.
