Horizontal Swab Insertion in Nasal Cavity for Viral Antigen Test

Although self-administered antigen tests are widely available, anatomical knowledge of nasal anatomy in the general population is limited. Cerebrospinal fluid leakage has been reported in multiple cases following damage to the roof of the nasal cavity due to accidental penetration of the cribriform plate of the ethmoid bone. Methods: Images of anatomical prosections used for teaching in the Dissection Room of the Faculty of Medicine of the University of Barcelona were obtained to illustrate the viable horizontal pathway to the nasopharynx through the inferior meatus, below the inferior turbinate. Screenshots from publicly available videos produced by the author demonstrating swab insertion were analyzed to measure the final insertion angle using 3D software. Publicly available instructions for patients included with authorized antigen tests in Spain were reviewed. Results: Antigen tests available in Spain in 2025 recommended a predominantly vertical swab insertion. However, successful horizontal insertion in the inferior meatus towards the nasopharynx can be achieved with a slight vertical angle of 7–9°. A schematic illustration for free use is provided. Conclusion: Swab instructions should be revised to emphasize an insertion perpendicular to the face in order to access the inferior meatus safely and reduce the risk of injury to the ethmoidal cells.