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Need explanation about RT-PCR results

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#1 Rapunzel


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Posted 03 October 2012 - 10:41 AM


I have some questions about my latest RT-PCR results.  I had to go with LabCorp and not Quest this time as my insurance changed the lab that is in network.  The format of the results changed and so I am unable to make sense of the new results.

Here are the results:

1. b2a2 transcript: 0.192

2. b3a2 transcript: 0.136

3. e1a2 transcript: ------

4.  <0.001% (Sensitivity limit of assay)

Transcripts: First of all, what are b2a2, b3a2 and e1a2.  I have never seen this in my Quest reports.  What do those numbers against the transcripts (0.192 and 0.136) signify?  I do not see any reference values and hence I do not know if this result is good or bad.  I do not have past results reported at the transcript level, so I cannot compare the data to see if my condition has become better or worse.

Log Reduction: The report says that the standardized baseline is 100% BCR-ABL.  So I think this represents 5 log reduction or more--Is this correct?  The previous RT-PCR results (done in August 2012) indicated 3.014 log reduction.  From this perspective I think that I am doing well.  Does 5-log reduction represent PCRU or MMR (Major Molecular Response)?

Other Details: DX in 11/2009.  On Gleevec from 11/2009 to 1/2011.  On Tasigna since 1/2011.

#2 TeddyB


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Posted 03 October 2012 - 11:28 AM

3 log reduction is MMR, 4.5 log reduction is CMR, not sure what a 5 log reduction is, i would think it is still CMR.

#3 Trey


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Posted 03 October 2012 - 02:24 PM

There are 3 main types of Ph+ chromosomes, also called junction variants, called b2a2, b3a2, and e1a2.   A junction variant means that when the Ph+ chromosomes are formed, they are formed by chromosome 9 and chromosome 22 each breaking at a certain point along the chromosome and trading places.  Most people only have only one type of Ph+ chromosome, either b2a2 or b3a2.  I have both of the most common ones (b2a2 and b3a2), and so do you.  You can read more about this in a previous posting:


So for those with both b2a2 and b3a2, you need to add the two PCR results together to get your total BCR/ABL PCR result.  So .192 + .136 = .328   It does not say explicitly that these numbers are percentages (it says "transcripts" -- is this the exact language?), and although they probably are percentages given the other information you provided, this issue needs to be clarified.  If they are not percentages, then your PCR result is much higher.

If the .328% is the correct result, that is less than 3 log reduction.  I would also assume that the 3 log reduction you were told about previously was incorrect since most lab techs do not know how to deal with multiple breakpoint PCRs.  But if the numbers you provided are not percentages, then your result is not nearly as good, so ask the Onc to make that point clear.

#4 Rapunzel


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Posted 03 October 2012 - 03:57 PM

Trey, Thanks very much for the explanation.  I see now that the transcripts are expressed in % (% appears under the Units column in the far right hand side of the report and I did not see that the first time).  So, as you say I must be 0.328% which is a little over 2 log reduction. ughhhhhh!

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