Which statement about testing suspected CSF leakage is correct?

Which statement about testing suspected CSF leakage is correct?

• A. Glucose testing is a reliable indicator of CSF leakage.
• B. Glucose presence is unreliable because blood also contains glucose.
• C. A positive glucose test guarantees CSF leak.
• D. Glucose testing is not used.

Answer: (B)

The main idea here is that identifying a suspected CSF leak relies on a CSF-specific marker rather than simple glucose testing. Glucose testing of nasal drainage is not reliable because glucose is present in blood and in many other fluids. If blood contaminates the sample, or if other secretions mix in, a glucose result cannot distinguish CSF from these fluids, so it cannot definitively prove a leak. CSF glucose can resemble serum glucose and may remain within normal ranges even when CSF is present, which means a positive glucose test does not confirm a leak, and a negative test does not reliably rule one out. For accurate confirmation, a CSF-specific test such as beta-2 transferrin (often used clinically) is preferred, sometimes along with imaging.

The main idea here is that identifying a suspected CSF leak relies on a CSF-specific marker rather than simple glucose testing. Glucose testing of nasal drainage is not reliable because glucose is present in blood and in many other fluids. If blood contaminates the sample, or if other secretions mix in, a glucose result cannot distinguish CSF from these fluids, so it cannot definitively prove a leak. CSF glucose can resemble serum glucose and may remain within normal ranges even when CSF is present, which means a positive glucose test does not confirm a leak, and a negative test does not reliably rule one out. For accurate confirmation, a CSF-specific test such as beta-2 transferrin (often used clinically) is preferred, sometimes along with imaging.