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 primary outcome was a postdose SCr increase > or = 0 . 5 mg / dL ( 44 . 2 micromol / L ) over baseline .
### Output Text:
The primary outcome was a postdose SCr increase > or = 0 . 5 mg / dL ( 44 . 2 micromol / L ) over baseline . 