In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: RESULTS : Compared to controls , aortic regurgitation ( OR : 3 . 1 ; 95 % IC : 1 . 1 - 8 . 8 ) and mitral regurgitation ( OR : 10 . 7 ; 95 % IC : 2 . 1 - 53 ) were more frequent in PD patients ( tricuspid : NS ) .
### Output Text:
RESULTS : Compared to controls , aortic regurgitation ( OR : 3 . 1 ; 95 % IC : 1 . 1 - 8 . 8 ) and mitral regurgitation ( OR : 10 . 7 ; 95 % IC : 2 . 1 - 53 ) were more frequent in PD patients ( tricuspid : NS ) . 