FISH vs. PCR

[Guest guest]

Hi " K " ,

I'm confused, too, but I know the tests are different. I think we have a

glossary on this page (maybe not yet) so you coulod look it up. Another site

with a complete glossary is www.cnksupport.org in the UK.

L

[ ] FISH vs. PCR

Hey Group:

I was diagnosed in 11/03, at that time I was told I had 39.5%

cancerous cells and over 800,000 out of 1,000,000 cancerous cells,

which I have never understood. I reached 'negative' in January and

received my last FISH results yesterday 'negative' again.

I haven't had a BMA since diagnosis and nothing has been said about

the PCR. I was told by a nurse that FISH & PCR are the same, I know

this is not true from information in this group.

I gather that the PCR test is a more sophisticated test, therefore

more expensive. Hmmmm. . . I have an HMO and from past experience I

know that some doctors don't offer tests that cost more when it's not

necessary. I would, however, like to know at this point whether or not

I am 0.00015 - 0.00057 as some of you survivors have stated from the

PCR test. 'Negative' means 'none' to me and I know that I have a

percentage in my blood and would like to know the 'exact' amount with

the margin for error.

Could someone please enlighten me on this??? It can be posted or

offlist.

I am fantastic as always, only tired all the time, and all my side

effects have subsided.

Thanx & I have you all in my prayers as always

" K "

" IAIN'TFINISHEDYET "

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[Guest guest]

Hi " K " ,

Understanding the various tests used to monitor CML can be difficult and the

doctors and nurses sometimes either don't explain the tests or do so poorly.

That can just make matters worse. You're right FISH and PCR tests are not the

same. You can get a really good explanation of FISH, PCR and cytogenetic tests

(all different) in the Winter 2003 issue of CML Update, which is the newsletter

from cmlsupport.com. To find the newsletter, just go to cmlsupport.com and look

for the link to newsletters, go to the Winter 2003 issue. The article begins on

page 1. One thing that's helpful to know in understanding PCR and FISH tests is

that they are methods of detecting the presence of the abnormal gene that

results in the disease CML. Genes contain DNA and DNA is a code for proteins

and some proteins are enzymes. Enzymes make things happen within a cell that

would not otherwise happen or they make things happen faster. In CML the

aberrant gene produces an enzyme (sometimes called

BCR/ABL) that makes white blood cells divide rapidly and become immortal. The

blood then becomes overrun with these white blood cells. These tests manipulate

the very special type of molecule that is DNA. If you could look at a DNA

molecule it would look like a ladder. The code is contained in the " rungs " of

the ladder. If you sliced the ladder in half lengthwise, i.e., down the length

of the rungs, you'd be able to separate it into two stuctures that each have the

backbone of the ladder and one half of each of the rungs. All the information

that's contained in DNA comes from just four molecules--A,T, C, G-- which

combine in a very precise way. A always pairs with T and C always pairs with G

(in living things molecules can combine with other molecules to make complex

molecules. DNA is a good example of a complex molecule) Each half rung of the

ladder represents A, T, C or G. If you put the ladder back together each rung

will be a combination of either A and T or C and G. So if

you want to find out if someone's blood cells contain a particular gene and you

know the sequence of the gene (the order of A/T and G/C pairs), you can

construct a " probe " that has the gene sequence you're interested in, subject the

blood cell DNA to special techniques that will " unzipper " the DNA (split it down

the middle as in my example) and then mix it with the probe. If the gene you're

looking for is in the blood cells, the probe will " hybridize " or attach to the

cell DNA where the sequence is a match. You can also isolate the DNA you're

interested in (extract it from the cells) and mix it with a probe in a test

tube too. FISH and PCR testing use this unique aspect of DNA to determine

whether a person's white blood cells contain the BCR/ABL gene. Neither test can

actually give you the exact number of cells with BCR/ABL or BCR/ABL genes in any

sample. But they can give you percentages and it's really the percentages over

time that matter because that will tell you if you're

disease is stabilized, progressing or continuing to decrease in magnitude. I

agree with you that zero means zero and if your PCR numbers are 0.00051 to

0.00057, that's not zero, but it's very, very low. Perhaps your doctor was

trying to say that it's equivalent to zero in his/her mind. Also keep in mind

that zero on PCR or FISH or any other test doesn't mean that you no longer have

the disease. It just means that the test did not detect whatever it was looking

for.

Sorry for the long post. I hope I haven't confused you further. The newsletter

article I mentioned tells you the pros and cons of each type of test in addition

to explaining the basic techniques, so I'd start there. Please let me know if

I've muddied the waters further.

Adrienne

iaintfinishedyet <kttweety@...> wrote:

Hey Group:

I was diagnosed in 11/03, at that time I was told I had 39.5%

cancerous cells and over 800,000 out of 1,000,000 cancerous cells,

which I have never understood. I reached 'negative' in January and

received my last FISH results yesterday 'negative' again.

I haven't had a BMA since diagnosis and nothing has been said about

the PCR. I was told by a nurse that FISH & PCR are the same, I know

this is not true from information in this group.

I gather that the PCR test is a more sophisticated test, therefore

more expensive. Hmmmm. . . I have an HMO and from past experience I

know that some doctors don't offer tests that cost more when it's not

necessary. I would, however, like to know at this point whether or not

I am 0.00015 - 0.00057 as some of you survivors have stated from the

PCR test. 'Negative' means 'none' to me and I know that I have a

percentage in my blood and would like to know the 'exact' amount with

the margin for error.

Could someone please enlighten me on this??? It can be posted or

offlist.

I am fantastic as always, only tired all the time, and all my side

effects have subsided.

Thanx & I have you all in my prayers as always

" K "

" IAIN'TFINISHEDYET "

---------------------------------

[Guest guest]

Hi K,

You're right, FISH and PCR's are totally different and as if that

wasn't confusing enough, there are different types of PCR's.

Generally speaking, a FISH test will look at about 200 cells and a

PCR will look at anything between 10,000 and 1 million cells. Again

you're right that the PCR is more sophisticated. It's more

sensitive so it can look at a much bigger picture. How useful it

is, is controversial as you'll see.

Some PCR's are qualitative which will give you a yes or no answer

(positive or negative). Either they saw leukemic cells or they

didn't. This type of PCR is of little value unless you're negative

on it because if you're positive, you want to know how positive and

you want to be able to track it....for instance, is it going up or

down from test to test.

This is where the quantitative test comes in as more useful. A

quantitative PCR will give you an actual number so you can see if it

goes up or down. If you're lucky, you'll get something like 0.00000

which of course would be no number but certainly a good result.

There is much controversy however on how good PCR's are because

they're a relatively new technology, there are alot of bugs to work

out and the tests are not standardized meaning that you could get

two totally different results from the same sample sent to two

different labs. So it is generally recommended that patients stick

with the same lab to track their results over time.

hope that helps,

Tracey

-- In , " iaintfinishedyet " <kttweety@s...> wrote:

> Hey Group:

> I was diagnosed in 11/03, at that time I was told I had 39.5%

> cancerous cells and over 800,000 out of 1,000,000 cancerous cells,

> which I have never understood. I reached 'negative' in January and

> received my last FISH results yesterday 'negative' again.

>

> I haven't had a BMA since diagnosis and nothing has been said

about

> the PCR. I was told by a nurse that FISH & PCR are the same, I

know

> this is not true from information in this group.

>

> I gather that the PCR test is a more sophisticated test, therefore

> more expensive. Hmmmm. . . I have an HMO and from past experience

I

> know that some doctors don't offer tests that cost more when it's

not

> necessary. I would, however, like to know at this point whether or

not

> I am 0.00015 - 0.00057 as some of you survivors have stated from

the

> PCR test. 'Negative' means 'none' to me and I know that I have a

> percentage in my blood and would like to know the 'exact' amount

with

> the margin for error.

>

> Could someone please enlighten me on this??? It can be posted or

> offlist.

>

> I am fantastic as always, only tired all the time, and all my side

> effects have subsided.

>

> Thanx & I have you all in my prayers as always

>

> " K "

> " IAIN'TFINISHEDYET "

[Guest guest]

Hey Group:

Thanx Zavie, Adrienne, Barb, & Roy. . . and anyone else who responds to my post.

You guys are great, and I am so happy that I found you. Thanx bro , and I

pray you feel better very soon.

, we got their attention. . . now we have to make sure they follow through.

It is so important to so many of my brother & sister survivors.

Take care and you are all in my prayers.

" K "

" I AIN'T FINISHED YET " !!!