Problem with NegEx negation

[jonquet]

For example, the two next sentences are essentially very similar (the same semantic meaning) and the only difference is the use of the "large" adjective in the first sentence (this example is extracted from the case CXR1255 in the Chest X-Ray collection from Indiana University):

No large pleural effusion
No pleural effusion
In the first case the NCBO Annotator returns an AFFIRMED annotation for the "Pleural effusion" class while the second case returns a NEGATED annotation for the same class.