Why is glucose testing unreliable for detecting CSF in nasal drainage?

Why is glucose testing unreliable for detecting CSF in nasal drainage?

• A. Because blood also contains glucose
• B. Because CSF has no glucose
• C. Because nasal drainage is not reliable
• D. Because glucose degrades quickly

Answer: (A)

The idea being tested is that glucose testing in nasal drainage isn’t reliable for confirming a CSF leak. CSF does contain glucose, but so does blood. If the drainage sample is contaminated with blood from a skull fracture or nasal bleeding, the glucose on a test strip could come from the blood rather than CSF, leading to a false impression of CSF leakage. Because of this lack of specificity, glucose testing alone isn’t trusted to diagnose a CSF leak. More specific tests, like beta-2 transferrin, are used to confirm CSF in nasal drainage.

The idea being tested is that glucose testing in nasal drainage isn’t reliable for confirming a CSF leak. CSF does contain glucose, but so does blood. If the drainage sample is contaminated with blood from a skull fracture or nasal bleeding, the glucose on a test strip could come from the blood rather than CSF, leading to a false impression of CSF leakage. Because of this lack of specificity, glucose testing alone isn’t trusted to diagnose a CSF leak. More specific tests, like beta-2 transferrin, are used to confirm CSF in nasal drainage.