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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Most definitive diagnosis of sinusitis is
assistant
The correct answer is  Sinuscopy or Diagnostic nasal endoscopy is the most appropriate investigation.The classical feature is the presence of mucopus in the middle meatus or above the middle meatusA more appropriate investigation would be CT scan of the nose and PNS.Ref: Hazarika; 3rd ed; Pg 331