A patient develops clear watery rhinorrhoea after endoscopic skull base surgery. Fluid is collected and sent for analysis to confirm a cerebrospinal fluid leak. Which laboratory finding confirms the fluid is CSF?
- A Presence of beta-2 transferrin ✓
- B Glucose concentration above 100 mg/dL
- C High sodium content compared with serum
- D Presence of tau protein
Correct answer: A. Presence of beta-2 transferrin
Explanation
Beta-2 transferrin is found almost exclusively in cerebrospinal fluid, perilymph and aqueous humour, making its detection highly specific for a CSF leak and the current gold standard test. Glucose testing of nasal fluid is unreliable because lacrimal secretions and nasal mucus also contain glucose, producing false positives. Sodium levels do not discriminate CSF from serous secretions, and tau protein is not used for this purpose.
Reference: Scott-Brown's Otorhinolaryngology and Head and Neck Surgery, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.