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: BUN and creatinine increased by > 50 % of baseline levels in 54 and 45 % of Group A patients , respectively , compared to only 20 and 10 % of Group B patients ( p < 0 . 05 ) .
### Output Text:
<span class="chemical">BUN</span> and <span class="chemical">creatinine</span> increased by > 50 % of baseline levels in 54 and 45 % of Group A patients , respectively , compared to only 20 and 10 % of Group B patients ( p < 0 . 05 ) . 