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 : Forty of 94 HIT patients had thrombosis at diagnosis ; 54 / 94 had isolated - HIT without thrombosis .
### Output Text:
RESULTS : Forty of 94 HIT patients had thrombosis at diagnosis ; 54 / 94 had isolated - HIT without thrombosis . 