Anosmia: an evidence-based approach to diagnosis and management in primary care.

Abstract

Anosmia is a relatively common presentation. The number of patients with smell disturbance is expected to increase over the next few months to years given its association with COVID-19 infection.1 Prior to the COVID-19 pandemic the point prevalence was 19.1%, including both complete and partial loss of smell.2 With a wide-ranging differential diagnosis, disturbance in smell can affect patients of all ages. The condition is significantly more common in advancing age, with around half of the population reporting disturbance in olfaction between 65 and 80 years, and even larger numbers >80 years.3,4 As one of our five key senses, disturbances in smell have a profound effect on patients’ quality of life, with strong associations with mental health disease.5 Smell is essential for protecting against dangers of day-to-day life, including smelling gas leaks and identifying spoilt food. Despite this, the condition is poorly understood and often dismissed as a symptom in both primary and secondary care. This may be as it is often accompanied by other, more well-understood conditions such as nasal blockage, or if it presents in isolation is thought to be a non-sinister symptom. Box 1 includes a list of definitions for anosmia and related conditions. | Anosmia | No perceivable sense of smell | || | Hyposmia | Reduced sense of smell | | Cacosmia/parosmia | Distorted or unpleasant sense of smell | | Phantosmia | Smell perception in the absence of a stimulus | Box 1. Definitions A basic understanding of the olfactory pathway will be reviewed to aid the understanding of smell perception. Disturbances at any of the points along this pathway can lead to a loss or alteration in smell. Smell is the detection of environmental organic molecules at the olfactory cleft.5 These stimuli are detected on the olfactory neuroepithelium. This is a small area of the nasal mucosa (approximately 2 cm2) located superomedially in the nasal cavity around the cribriform plate.4,5 In order for an odorant to be detected, it has to pass uninhibited into …