All are helpful for the diagnosis of CSF rhinorrhea except:

Following trauma of the midface, CSF may emanate from a dural tear, resulting in rhinorrhea, otorrhea, or both.  The  disruption  usually  occurs  lateral  to  the  cribriform plate but may also result from disruption of the sphenoidal,  ethmoidal,  and  frontal  sinuses  producing  a  dural tear and communication with the subarachnoid space. Diagnosis of CSF leakage is often complicated by mixture with nasal secretions, lacrimal  secretions, and blood. Clear CSF should be collected in a vial, an absence of sediment and a glucose level of approximately 45 mg/dL is usually confirmatory.  A more specific, albeit slower, laboratory examination is the CSF-specific beta-2 transferrin test. CSF  will  also  form  concentric  rings  when poured on linen or soft filter paper.  CSF has a more rapid diffusion than blood, leading to a larger, clearer CSF ring surrounding a sanguineous central ring. This is termed the double-ring or halo sign. When bleeding is present, one should suspect the presence of a CSF leak until proven otherwise. Once a provisional diagnosis is made, the patient should be placed in a semirecumbent position and instructed on how to minimize increases in intracranial pressure, including straining, sneezing and blowing of the nose. Meningitis  is  a  potential  complication  of  skull  base fracture with a concomitant dural tear. The absence of leakage does not imply the absence of a tear.  Reference: Fonseca 4th ed page no 437,439