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: Liver function tests , hepatitis B virus ( HBV ) serologic markers , and HBV DNA levels of the patients during follow - up were obtained from hospital file records .
### Output Text:
Liver function tests , hepatitis B virus ( HBV ) serologic markers , and HBV DNA levels of the patients during follow - up were obtained from hospital file records . 