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: Decreased renal function was defined as a rise in serum creatinine > / = 0 . 5 mg / dL ( 44 micromol / L ) from baseline .
### Output Text:
Decreased renal function was defined as a rise in serum <span class="chemical">creatinine</span> > / = 0 . 5 mg / dL ( 44 micromol / L ) from baseline . 