IS conversion factors

Hi David,
not sure I can help with specific local lab value for Barts but I can tell you the CF for Hammersmith..see below.

The American Cancer Soc. published the following on how to calculate for conversion to IS:

Conversion Factor: How a specific local lab value is calculated to allow for conversion to IS

In order to convert a given local result to the international scale, it is necessary to use a conversion factor (CF). This is calculated as follows: CF = 0.1% divided by MMREq (since 0.1% is the agreed value for MMR on the international scale). Once a laboratory-specific conversion factor has been derived, it can be used to convert all local values to the international scale. (This calculation will be invalid if the reproducibility or linearity of the assay is poor, in which case the methodology will need to be optimized.)
Copyright © 2006, American Society of Hematology

So in the following example calculating your PCR result on the International Scale if your testing lab is Hammersmith would go as follows:

London Hammersmith MMREq,% is 0.045- Divide this % by 0.1% (MMR on IS) and you get a CF of 2.22 or the International Scale Conversion Factor for the Hammersmith Lab.
In my own example my latest PCR result shows the percentage of BCR-ABL1 to be at 0.001% - I am happy with that as it has been the same from the HH lab for the last 2 years. However, if I multiply that result by 2.22 to get a % according to the IS....then I get 0.00222% BCR-ABL. I am also happy with that ;o)

BTW.. I have just tried to replicate the HH CF by calculating it according to the American Cancer Society explanation- but failed to get 2.22- not sure what I am doing wrong but my maths is pretty sub-optimal.

Hope this helps!
Sandy