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: Plasma TAFI , tPA , and PAI - 1 antigen levels were measured at baseline and after 3 months of treatment by commercially available ELISA kits .
### Output Text:
Plasma TAFI , tPA , and PAI - 1 antigen levels were measured at baseline and after 3 months of treatment by commercially available ELISA kits . 