Final answer:
The lab test with the worst prognosis for CHF patients is elevated BNP or NT-proBNP levels, which reflect severe ventricular dysfunction and hemodynamic stress.
Step-by-step explanation:
The lab test that carries the worst prognosis in patients hospitalized with Congestive Heart Failure (CHF) is elevated blood levels of BNP (B-type Natriuretic Peptide) or its N-terminal pro hormone NT-pro BNP.
These markers are synthesized in response to ventricular volume expansion and pressure overload, which are common in CHF patients.
High levels of these peptides typically indicate a worse prognosis because they reflect the severity of the hemodynamic stress and the degree of ventricular dysfunction.
Other lab tests that can indicate a poorer prognosis include elevated serum creatinine, which indicates compromised kidney function; and hyponatremia, which indicates a more advanced stage of heart failure.