Postinfectious Olfactory Complaints: A Follow-up Study.

Acute upper respiratory infection (AURI) is the most common cause of postinfectious olfactory dysfunction (PIOD).  We investigated the prevalence of PIOD in a large group of patients reporting persistent smell impairment perception after the AURI resolution.  Olfactometry was performed within 1 month after the common cold resolution and after 1 year in 467 (299 males, mean age 41.7 years) outpatients. The Sniffin' Sticks olfactory test (Burghart instruments, Wedel, Germany) was used.  Anosmia was documented in 28 (6%) patients, hyposmia in 33 (7%), and cacosmia in 55 (11.7%). After 1 year, PIOD improved in 82 (79.6%) patients re-tested.  The current study demonstrated that persistent olfactory dysfunction is a relevant symptom in patients with AURI, even though many patients had normal olfactometry. Thus, smell impairment deserves careful attention and requires objective documentation.