Bloody drainage from the ear; which test confirms presence of CSF in the drainage?

• A. Collect 5 mL of fluid in a test tube and send it to the laboratory for analysis.
• B. Test the fluid with a glucose-identifying strip or stick.
• C. Examine the tympanic membrane for a tear.
• D. Test the fluid for a halo sign on a white dressing.

Answer: (D)

When there’s bloody drainage from the ear after head injury or surgery, you want a quick bedside way to confirm CSF in the drainage. The halo sign on a white dressing is the best indicator here because CSF is clear and will diffuse into the surrounding white fabric, creating a distinct clear halo around the central bloodstain. This visual pattern strongly suggests that CSF is present in the drainage.

Other options are less specific at the bedside: collecting fluid for general lab analysis takes time and may not be readily available; a glucose strip isn’t definitive since glucose can be present in other fluids and can be confounded by blood; examining the eardrum shows a tear but doesn’t confirm the fluid’s composition.