That's very good news.
The NIH-funded research found the connection by a trial-and-error method:
Using mass spectrometry, the scientists screened a large number of proteins in the blood and skin of bone marrow transplant patients to search for biomarkers involved in GVHD of the skin. Elafin emerged as a significant biomarker.
Treatment choices are often a balancing act, and being able to tell whether or not a patient has GVHD of the skin, using a blood test, will take some of the guesswork out of it.