<prompt> Most definitive diagnostic of sinusitis is:X-ray PNSProof punctureNasal endoscopyTransillumination test  <response>: Nasal endoscopy is the most definitive diagnostic of sinusitis. It is done to see the various sinus meatuses, mucopus or any other pathology. If mucopus is seen in the meatus, it is confirmatory of sinusitis. 