And sort of how do you differentiate between the different PFIX subtypes?

So at last count there are 13 so that makes it very difficult.

The usual way to approach it is to really sort of look at the GTT and they're probably two main subgroups.

There's people with maybe a primary cholestasis which may be a hepatocyte cholestasis.

They can't get rid of the bile from their hepatocytes and then there's another group which has more of a cholangitis.

or a cholangiopathy type presentation where the bile is damaging their bile ducts and their biliary tree.

And the main way to differentiate that would be the GGT level.

And how do you explain genetic testing and how do you interpret a variant of uncertain significance?