Table 4.

Clinical NER: impact of the source of unlabeled corpus.

Unlabeled corpus	Exact F	Inexact F
None	80.3	89.7
Medline	81.9	91.0
UT Houston	82.3	91.3
Mayo	82.0	91.3

Notes: None = The machine-learning clinical NER system that does not use any distributional semantic features. Medline = The machine-learning clinical NER system that uses distributional semantic features derived from the Medline abstracts indexed as pertaining to clinical trials. UT Houston = The machine-learning clinical NER system that uses distributional semantic features derived from the notes in the clinical data warehouse at University of Texas Health Sciences Center. Mayo = The machine-learning clinical NER system that uses distributional semantic features derived from the clinical notes of Mayo Clinic, Rochester, MN.