What are the appropriate diagnostic steps and potential treatments for an individual with anosmia?

Anosmia: Diagnostic Approach and Treatment

For patients presenting with anosmia, immediately initiate olfactory training with four strong-smelling substances for 20 seconds each, twice daily, combined with intranasal corticosteroids (fluticasone or mometasone), while simultaneously pursuing diagnostic evaluation to identify the underlying cause. 1

Immediate Diagnostic Steps

COVID-19 and Viral Testing

• Test all patients with new-onset anosmia for SARS-CoV-2, as 59-86% of COVID-19 patients develop chemosensory loss, and isolated anosmia can be the sole presenting feature in up to 22% of cases 2
• Anosmia has 98.7% specificity for COVID-19 screening, though sensitivity is lower at 22.7% 2
• Traditional nasal symptoms (congestion, rhinorrhea) are frequently absent in COVID-19-related anosmia, unlike other viral URIs 2
• Viral upper respiratory infections account for 20-25% of specialist clinic presentations with olfactory disturbances 3

Objective Olfactory Testing

• Perform standardized psychophysical testing using UPSIT (University of Pennsylvania Smell Identification Test) or Sniffin' Sticks to objectively quantify dysfunction 3, 4
• Do not rely on patient self-report alone—one study showed 98.3% had objective olfactory dysfunction by UPSIT even when only 35% self-reported complaints 2
• Patients commonly underestimate their impairment, making objective testing mandatory 5, 4

Nasal Examination

• Rigid nasal endoscopy is mandatory to differentiate between obstructive causes (polyps, masses, tumors) and non-obstructive inflammatory causes 2
• Anosmia with nasal congestion suggests a conductive mechanism, while anosmia without nasal obstruction symptoms suggests sensorineural pathology 3
• Chronic rhinosinusitis accounts for a significant proportion of chronic olfactory dysfunction cases and requires endoscopy to identify polyps, inflammation, or obstructing masses 2

History Taking

• Obtain detailed temporal relationship with viral infections and associated symptoms 3
• Insidious onset over weeks-to-months suggests metabolic or structural causes rather than post-viral causes 2
• Sudden onset without nasal symptoms may indicate COVID-19 or other viral causes 2

Treatment Protocol

First-Line Treatment: Olfactory Training

• Start olfactory training immediately, involving sniffing four different strong-smelling substances (e.g., rose, eucalyptus, lemon, clove) for 20 seconds each, twice daily 1
• Continue for at least 3-6 months regardless of etiology 2
• Olfactory training can lead to significant improvement of post-viral olfactory deficits 6

Pharmacologic Adjunct

• Add intranasal corticosteroids (fluticasone nasule or mometasone spray) for post-infectious olfactory dysfunction 1
• Systematic review evidence supports efficacy for post-viral cases 1
• Fluticasone and mometasone are therapeutically equivalent for this indication 1

Timing Considerations

• At 6 weeks post-URTI, patients are in the appropriate window for intervention, as symptoms persisting beyond 10 days but less than 3 months represent evolving post-viral dysfunction 1
• Anti-inflammatory drugs and surgery can help in select cases 6

Follow-Up and Referral

Monitoring Schedule

• Re-evaluate at 1 month, 3 months, and 6 months after initiating treatment 1, 2
• If no improvement after 3-6 months of olfactory training plus intranasal corticosteroids, refer to otolaryngology or a specialized smell and taste clinic 1, 2

Advanced Imaging

• Neuroimaging (MRI with olfactory protocol) should only be considered if symptoms persist beyond 6 months despite therapy 1, 2
• CT sinuses may be indicated if chronic rhinosinusitis is suspected on endoscopy 2
• Do not routinely image for primary diagnosis of smell loss 4

Safety Counseling

Counsel all patients on safety precautions:

• Install gas and smoke detectors 1
• Maintain vigilance about food expiration dates 1
• Olfactory dysfunction impairs the ability to sense warning odors in foods and the environment 7

Special Populations and Red Flags

Neurodegenerative Disease Screening

• Olfactory dysfunction is an early sign of neurodegenerative disease, with the majority of Parkinson's and Alzheimer's patients having olfactory loss early in their disorder 6
• In Parkinson's disease, olfactory impairment precedes motor symptoms by years 5
• In Alzheimer's disease, the severity of disease and olfactory disorder correlate 5
• Consider neurology referral if other neurologic signs are present 2

Age-Related Considerations

• Anosmia increases with advancing age, with high rates over age 70 due to changes in olfactory epithelium and reduced neuroregeneration 5
• Risk of olfactory dysfunction increases with old age, chronic sinonasal diseases, severe head trauma, and neurodegenerative diseases 7