45 replies to this topic

[LivingWellWithCML]

Definitely Trey - that is an excellent recommendation for anyone who has their PCR testing run on-premise.  Thanks for encouraging me to look into this further!

[Lucas]

Great tópic. Thanks to trey and dan!! One last question: refrigerate the sample help to prevent sample's degradation; doesn't it?

[Trey]

Lucas,

Refrigeration only extends the useful life of the sample to a maximum of about 48 hours.

 

If RNAlater is used it apparently can extend the sample life, but it requires proper procedure for the PCR.  I am not sure how many labs use it.

Edited by Trey, 24 August 2014 - 07:04 PM.

[Lucas]

Thanks so much, trey. I got my last PCR today - 7 months with rnalater - and the result was 2.91% IS.

[thomaskk]

Great news Lucas . You are on your way to MMR within one year. Congratulations

Thomas

[mark1963]

I live in eastern PA and use and my local hospital sends it out to Labcorp. The report says Durham NC. Is this right? I know when I used Quest, I was never positive there, it said Chantilly Va. . Most report completed 4-5 days after draw. The phlebotomist said it is sent somewhere in NJ by courier for Labcorp. so why does report say NC. Is there any  labs in eastern PA that due PCR? My onc says he prefers genoptics? my quickest turnaround was actually a saturday draw that was finalized on a Wednesday afternoon.

I spiked last summer at .03 and went 4 tests at pcru and now a .07 out of nowhere. is pcru to .07 still within margin of error it still is MMR right?

mark 

[Trey]

That report is probably just using the LabCorp corporate headquarters near Durham, NC.  The sample would likely have been processed somewhere else.

[Lucas]

Hi, trey!

 

I have one more question about PCR: if the amounts of a control gene are less than 10.000 transcripts, the result will fluctuate up or down (or both)?

p.s.:My lab runs pcr with less than this (around 7.000 - 8.000 transcripts of abl1)

[Trey]

Lucas,

Not enough information.  Which lab does the PCR?

[Lucas]

Sorry, trey. it's a brazilian lab. the method is real time PCR - bcr-abl mbcr - IS MMR- kit - ipsogen. the real question is: does the number of the control gene (abl in that case) used in the test influences in the result? if the number of copies are less than 10 K, the result will vary up or down?

 

Thanks in advance

[Trey]

Your question assumes the amount of the control gene in the blood sample decreases as the patient's leukemia diminishes, which is not accurate.  ABL1 is the primary control gene used in most CML PCRs, and is a normal gene found in the human body.  BCR-ABL is, of course, abnormal.  The purpose of the PCR is to determine the ratio between BCR-ABL and ABL1, which provides an estimate of leukemia levels in the body by comparing the quantity of leukemic genes to normal genes.  So the PCR shows we are making progress if the leukemic genes (BCR-ABL) decrease in proportion to good genes (ABL1, in this case).  So the amount of ABL1 in the blood sample should be relatively constant over our lifetime regardless of our drug response, but we hope to see the amount of BCR-ABL decrease in relation to ABL1.  That means if we are making progress, the numerator (BCR-ABL) decreases as the denominator (ABL1) remains relatively constant, and this results in a decreasing PCR percentage until the numerator is zero, which is PCRU.

 

Ipsogen uses ABL1 as the control gene:

http://www.iuhealth....p210_update.pdf

[Lucas]

i think i understand better now, trey. My bcr-abl ratio is declining, but i thought that the number of the control gene was the number of the anilased transcripts and that the more transcripts analised, more accurate the result (if with add the number of the control gene to the bcr-abl, the total analised transcripts is always around 7-8K, with a steady decline in the bcr number and increase in the abl1, and i thought that it was necessary more transcripts to have a more accurate result), but it seems it doesn't matter too much. I think i had a wrong perception of the pcr exam.

 

Thanks again for the patience.

[Trey]

You are thinking too hard about this.  PCRs are an estimating process and and not exact.  And most PCRs have about the same sensitivity and quality.  Ipsogen is equivalent to most other PCRs, so your results will be close enough. 

[Lucas]

Thanks again trey. maybe it's just paranoia because i'm waiting for another pcr - from the third different lab

[gianfranko]

I am probably posting this too late in the discussion.  But, for whatever is worth, when my wife's PCR is tested by Quest Diagnostics (FL) she is PCRu.  When she is tested by Genepath (FL), she is PCRu.  When she is tested by Genoptix (CA), she is MMR.  This has happened because she had switched insurances and different insurances have different lab networks.  So would this imply that Genoptix is the better lab of the three?

[Trey]

GF,

 

Not better, but some labs allow PCR BCR-ABL reporting at lower levels.  Genoptix allows reporting down to -4.5 log, while the others truncate it at -4 logs.  This does not mean more sensitive.  Virtually all PCRs can detect down below 5 logs, but the false positives become very high at around -4 log, so most labs cut the reporting off at -4 log. 

[Lucas]

i got another pcr from the third lab - one of my doctors order this one less than two weeks of my last one. that lab uses bcr as control gene - the others runs abl1 - and uses taqman machines. the result was 6% (3% bcr-abl/bcr ratio). my result from the other lab - abl 1 gene and ipsogen - was 2.9% IS. i really don't know what to think about this mess.

[LivingWellWithCML]

Variation in control gene is one of the variables, and I can't tell if the former is on International Standard.  Who knows.

 

My advice is to look at your last FISH test result and see where are you on reaching CCyR (which is negative or 0% FISH).  Once you reach that milestone, then the PCR test results become more relevant for monitoring molecular response.  CCyR roughly corresponds to a PCR of < = 1%.  What was your last FISH test result?

 

BTW, I know how you feel.  I have agonized over this stuff way more than I should have (as you can tell by my crazy calls to PCR lab techs) - the stress and number crunching can be harder on us sometimes than CML!

[Lucas]

Thanks, dan! Actually, i think all the results were in IS (there's a convertion factor) but the control gene was different. I also know that pcr can vary 0.5 log and this result is on this margin (both exams around 7 months of therapy. one was 2.9% and other 6%). I not really worried about this result, i'm frustrated only. I think i'll have to wait one more month to have another pcr. 

 

About the Fish, we don't run much FISH here, we use cytogenetics tests and i'm waiting for the result too, so, fingers crossed

[Buzzm1]

when I have my PCR test done quarterly, I always call attention to the fact that the vial needs to immediately be refrigerated ... 

... the vial used already contains the stabilization agent

I go on a Monday, or a Tuesday, early in the day, so that they transport it before traffic gridlock begins setting in at 3pm

 

can't take too many precautions