There probably is, but I'm not 100% sure on how I would accomplish that, considering I'm still fairly green with creating addons.
I have an idea on how to do it, but since the text in question usually wraps to a second line in the tooltip and the break point for the wrap can be different for each item depending on the tooltip frame size, I'm not sure how to grab the whole thing and yank it out.
In my head I would do something like this, but from my understanding this would not actually work with the way I currently code the addon and the wrapping.
Lua Code:
string.gsub(string.find(_G[self:GetName().."TextLeft"..i]:GetText(), ^_G["USE"] .* _G["ITEM_QUALITY6_DESC"], "Artifact Power Percent: " .. string.format("%3.5f", appercent) .. "%")