Three days after head injury, a patient reports clear watery discharge from one nostril, worsened on bending forward. A drop of the fluid placed on a filter paper leaves a central stain of blood surrounded by a paler ring. Which test definitively confirms that the fluid is cerebrospinal fluid?

• A Beta-2 transferrin assay ✓
• B Glucose oxidase dipstick
• C High-resolution CT cisternography with intrathecal contrast
• D Protein electrophoresis showing tau protein

Explanation

Beta-2 transferrin is present almost exclusively in cerebrospinal fluid and aqueous humour, so its detection in nasal secretions confirms a CSF leak with high sensitivity and specificity. The glucose dipstick is unreliable because lacrimal secretion and nasal mucus also contain glucose, giving false positives. High-resolution CT is used to localise the defect once the leak is confirmed. Tau protein is another CSF marker but beta-2 transferrin is the established confirmatory test in exam and practice convention.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.