In the evaluation of suspected CSF leakage after cranial surgery, which test helps confirm the presence of CSF in drainage?

• A. Beta-2 transferrin test
• B. Gram stain
• C. Serum glucose
• D. Electrolyte panel

Answer: (A)

Distinguishing CSF leakage from other drainage after cranial surgery relies on a marker unique to CSF. The beta-2 transferrin test looks for a transferin isoform found specifically in CSF (and in a few other CSF-containing fluids) but not in blood or typical nasal secretions. A positive beta-2 transferrin result confirms that the drainage is CSF, which is crucial for guiding management and preventing complications like meningitis.

Gram stain would only reveal bacteria or cells if an infection is present, not confirm the fluid’s identity. Serum glucose and electrolyte measurements reflect the patient’s blood chemistry, not the CSF content of the drainage, so they are not reliable for confirming CSF leakage.