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 : The sensitivity improved dramatically from 16 % to 79 % , positive predictive value increased from 60 % to 68 % and negative predictive value from 54 % to 78 % , and specificity decreased from 90 % to 67 % .
### Output Text:
RESULTS : The sensitivity improved dramatically from 16 % to 79 % , positive predictive value increased from 60 % to 68 % and negative predictive value from 54 % to 78 % , and specificity decreased from 90 % to 67 % . 