Hi Frank,

A log (logarithm) is really just a way to re-scale numbers. Why the medical profession wants to use a log scale to describe results to non mathematical people is a complete mystery. Using more simple ratios is I guess just too simple!!!

If you are into maths then an explanation of the log scale (showing some really good reasons for using a log scale) is here:

http://en.wikipedia.org/wiki/Logarithm

A log scale can be based on anything, so it is technically wrong to talk about a log scale without saying what base you are using. In the CML context a base of 10 is being used. A natural base (e) is the one I use most but base 10 is also pretty common. If you are using a standard scientific calculator (iPhone users rotate your screen to landscape) base 10 will probably appear as "log" and base e will appear as "ln". I would like to write log followed by subscript of 10 but the formatting in here is not agreeable so I will write log.

The log scale is being used here to make the ratio of your PCR results more compact (& possibily harder to understand). Your log reduction is given by the following:

Log change from dx = log (PCR at dx / PCR now)

Log change from some other time point = log (PCR then / PCR now)

If your PCR at dx was 100 and your PCR now is 10 then, log change = log (100/10) = log (10) = 1

If your PCR at dx was 1 and your PCR now is 0.1 then, log change = log (1/0.1) = log (10) = 1

So as you can see the log is just another way of looking at the ratios of you PCR results.

If the ratio is greater than 1 (i.e. your numbers are decreasing) then the log change will be positive, or a log reduction

If the ratio is 1 (i.e. no change) then the log change is zero

If the ratio is less than 1 (i.e. your numbers are increasing) then the log change is negative, or a log increase

A shift of one decimal place, or one order of magnitude is 1 log (base 10) change. A shift of 2 decimal places, or two orders of magnitude is a 2 log change.....

If you look at your most recent PCR of 0.01 compared to your 2/09 PRC of 0.2 then the log change is log(0.2/0.01) = log (20) = 1.3 (positive number representing a log reduction)

Unfortunately (or fortunately for you) your 2nd last result is a PCRU i.e. 0 so if we did a log of zero it would be negative infinity i.e. you can't calculate a log increase using a PCRU

If you compare you 3rd last result with your last result the your log change is log(0.008/0.01) = log(0.8) = -0.097 (negative number representing a log increase)

What exactly this means I am not well placed to say, but I do note that you went from PCRU to 0.01 before and then back to PCRU again.

Best wishes.

Josie

Dx Dec 2010 @37

2x IVF egg collection

Glivec 600 & 800mg

PCRU March 2012

Unsuccessful pregnancy attempt - relapsed, 3 months interferon (intron A), bad side effects from interferon

Nilotinib 600mg Oct 2012

PCRU April 2013, 2 years MR4.5 mostly PCRU with a few blips

April 2015 stopped again for pregnancy attempt (donor egg), pregnant first transfer, 0.110 at 10wks, 2.1 at 14wks, 4.2 at 16wks, started interferon, slow dose increase to 25MIU per wk, at full dose PCR< 1 for remainder of pregnancy

Healthy baby girl Jan 2016, breastfed one month

Nilotinib 600mg Feb 2016

MMR May 2016

PCRU Feb 2017