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: CONCLUSION : Higher OD is associated with significant risk of subsequent thrombosis in patients with isolated - HIT ; percent inhibition , however , was not predictive .
### Output Text:
CONCLUSION : Higher OD is associated with significant risk of subsequent thrombosis in patients with isolated - HIT ; percent inhibition , however , was not predictive . 