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: Diagnostic markers such as N - terminal pro brain natriuretic peptide ( NT - proBNP ) or high - sensitive C - reactive protein might help in the early identification of patients at risk , thus avoiding the occurrence of serious cardiovascular toxicity .
### Output Text:
Diagnostic markers such as <span class="chemical">N - terminal pro brain natriuretic peptide</span> ( <span class="chemical">NT - proBNP</span> ) or high - sensitive C - reactive protein might help in the early identification of patients at risk , thus avoiding the occurrence of serious cardiovascular toxicity . 