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: The Receiver Operative Characteristic Curve showed that OD > 1 . 27 in the isolated - HIT group had a significantly higher chance of developing thrombosis by day 30 .
### Output Text:
The Receiver Operative Characteristic Curve showed that OD > 1 . 27 in the isolated - HIT group had a significantly higher chance of developing thrombosis by day 30 . 