Color Change of Intranasal Fluorescein Cannot Detect Cerebrospinal Fluid Leaks

Background: The color change of topical intranasal fluorescein has been used to confirm the presence of cerebrospinal fluid (CSF) during endoscopic endonasal surgery. We aimed to validate the use of topical intranasal fluorescein for CSF detection. Methods: Blood, CSF, saliva, and normal saline were combined with decreasing fluorescein concentrations (from 10% to 0.1%). The solutions were photographed in high definition on nasal pledgets and in 1.5-mL Eppendorf tubes. The color difference (ΔE) was objectively measured via the International Commission on Illumination coordinates. Four otolaryngologists who were unaware of the study parameters also evaluated the samples for perceptible color differences. The human eye cannot detect color differences at an International Commission on Illumination ΔE of <5. Results: All otolaryngologists agreed a color difference could be seen with blood across all fluorescein concentrations. However, a perceptible color difference between the experimental samples that excluded blood was not appreciable. Objectively, the ΔE was <5 on average for all nonblood samples when mixed with 5% and 10% fluorescein in the Eppendorf experiment. The ΔE for the nonblood samples was >5 for the remaining tested. Similarly, the average ΔE for the nonblood samples in the pledget experiment was >5 across all fluorescein concentrations. The blood ΔE was consistently >50 throughout all fluorescein concentrations in the Eppendorf experiment and >20 throughout the pledget experiment, correlating with the subjective ease of discernment between blood and the control sample in both groups. Conclusions: Color change alone is not sufficient to determine a difference between CSF, saliva, and saline. Blood, however, is readily identified using this method. Adjunct characteristics, in addition to the color change, are necessary to properly identify an active CSF leak.