
In most cases you don't need to add acronyms or their definitions at all: PerfectIt finds acronyms and links them to their definitions with over 90% accuracy straight out of the box.
But some abbreviations are hard to detect automatically, especially acronyms with numbers or hyphens in them. You can add those in Styleworks to improve PerfectIt's accuracy.

Steps
Write the definition together with the abbreviated form, either order works:
extensively drug-resistant tuberculosis (XDR-TB)
Now PerfectIt will search for XDR-TB in the same way it looks for other acronyms.
