Ageusia is a rare condition that’s characterised by the complete loss of taste in the tongue. It is usually not life-threatening but can significantly impact quality of life. Some accompanying symptoms of ageusia include loss of appetite, weight loss and in some cases, patients need to stop medication that worsens taste disturbances. 

The COVID-19 pandemic brought ageusia into public awareness. Many people reported a loss of taste and smell before, during and after infection, bringing ageusia to the forefront of research interest and clinical attention. For primary care providers like GPs, pharmacists, dentists and other first-contact clinicians, understanding how to evaluate ageusia and taste loss is very important in helping treat patients confidently. This article focuses on ageusia and how it can be diagnosed in primary care settings today following COVID. Read more to find out!

Once a patient presents with ageusia, the main objective of a clinician is to identify the cause, explain the rationale and review the treatment options with the patient. Although ageusia is not a life-threatening condition, it can cause discomfort and a negative impact on the quality of life. Therefore, it is a point of interest for current research. Some other common symptoms include weight loss, loss of appetite. In severe cases, it may require discontinuation of certain drugs.

Many things can cause ageusia. Some examples include damage to nerves that are responsible for taste, such as the lingual and glossopharyngeal nerves on the top or bottom part of the tongue. Other causes include dietary deficiency and conditions like diabetes and hypothyroidism. In addition, aguesia could also be caused by cranial nerve lesions affecting the gustatory or tasting function, such as neuritis due to herpes zoster, meningioma or neurinoma, and dissections of cervical arteries. In some cases, it can also result from wounds or scratches caused during an examination by a physician, like laryngoscopic manipulations or anaesthesia, also known as iatrogenic lesions.

Zinc deficiency can be linked to abnormalities with taste perception in otherwise healthy people and is sometimes the cause of taste loss in drug-induced taste disorders. Local injury and inflammation, of course, can cause loss of taste, but certain types of drugs like antibiotics, neurologic medication, and cardiovascular drugs may also contribute.

All in all, ageusia is hard to treat because it can be caused by many things. Therefore, identifying the specific cause is a fundamental step in treatment. In terms of complete loss of taste, ageusia is quite rare, affecting 1 or 2 people in 1000. As we age, our sense of taste naturally declines; However, an ageusia diagnosis requires a complete loss of taste, which is quite rare and only affects 1 or 2 people in 1000.

How ageusia is diagnosed in primary care settings

Primary care settings refer to the first point of contact in the health care system. In practical terms, it includes care provided by GPs, community pharmacists, opticians, and dentists. When someone presents with ageusia, the patient's detailed medical history is collected first to identify the cause of the disease and to see if any recent events could be associated with the onset. This part involves gathering a complete patient history, including current medication and dental procedures.  conducting a subjective assessment, as well as a physical examination of the head, neck, and oral region.

A variety of tests are available to assess the taste sensations at this point. Diagnostic tools include taste strips, where the patient is asked to distinguish among certain tastes such as sweet, salty or sour, to assess the intensity of the damage. The tests are separated into 2 main categories: electrogustometry and chemogustometry. Electrogustometry means that weak electrical currents are applied to different taste buds, whereas chemogustometry means that specific taste solutions are applied. The primary purpose of these tests is to identify if the source of the ageusia is local, or related to systemic conditions, or lesions in the central nervous system.

Ageusia and COVID-19

Loss of taste (ageusia) as well as smell (anosmia) came as unexpected symptoms of COVID-19, reviving academic interest in ageusia. Interestingly, in a study by Paetl et al., patients who reported loss of taste couldn’t accurately differentiate between losing their taste or smell. This may be due to the fact that the gustatory system recognises basic tastes like sweet, sour and salty, while it is the olfactory nerveresponsible for our culinary experience. This suggests that smell has a huge influence on the way we perceive tastes. Hence, diagnostic investigation in ageusia should extend to investigating the olfactory nerve as well.

In the context of COVID-19, the sudden onset of taste and smell loss was a useful early diagnostic indicator. A new type of diagnostic measure for COVID-19 detection in primary care was reported by Higa et al. They used smartphone voice recordings from patients to detect vocal biomarkers. The biomarkers were then fed into an artificial intelligence-based algorithm to predict the presence or absence of ageusia associated with COVID-19. They were able to identify 2 biomarkers and make accurate predictions about the presence of ageusia and COVID-19, which highlighted the importance of integrating digital health solutions as a means of enhancing virtual consultation and telemonitoring. Future directions in this field involve further external validation studies across diverse populations and languages.

Additional tests

Because smell and taste are so closely linked, GPs can also use olfactory tests to check if loss of smell is causing ageusia. These tests include scratch-and-sniff cards, essential oils, or standard smelling kits to assess the sense of smell.

Laboratory tests can also be used to check for other underlying causes. These include blood tests for zinc, iron, or vitamin B12 deficiency, thyroid function tests to rule out hypothyroidism, and blood sugar tests to check for diabetes. It is essential to investigate these conditions when evaluating taste disorders.

If the cause isn’t clear, the primary care provider can then refer patients to specialists such as ENT(ear, nose and throat) specialists, neurologists, or dentists. They will be able to check for other causes, such as nerve or sinus-related issues, central nervous system causes, or oral health problems, respectively.

Imaging and advanced diagnostic tools like MRI or CT scans may also be used to rule out causes like tumours or nerve compression, but these are usually not included in primary care. Screening tools, like the ones mentioned above, using AI-assisted diagnostics along with smartphone-based smell and taste assessments, are currently in development to help primary care providers identify ageusia earlier and more accurately.

Summary

• Ageusia is a rare condition characterised by the complete loss of taste
• During the COVID-19 pandemic, many people reported loss of taste and smell, which emerged as a useful early diagnostic clue for COVID-19
• Primary care refers to the first point of contact a patient has when they go to the doctor for a problem
• Common diagnostic measures for ageusia include taste strips, electrogustometry (electrical stimulation of taste buds), and chemogustometry (application of taste solutions)
• Causes of ageusia can include nerve damage, nutritional deficiencies, systemic diseases, infections, medications, and iatrogenic injuries
• Assessment in primary care may also involve reviewing patient history, performing head, neck, and oral examinations, and occasionally ordering lab tests or diagnostic imaging if needed
• Ageusia, while not life-threatening, can impact appetite, nutrition, quality of life, and medication adherence

FAQs

What are the different types of taste disorders?

Ageusia is defined as the complete loss of taste. However, we also have hypogeusia, which is a reduced ability to taste, dysgeusia, which is experiencing distorted or unpleasant taste, and finally anosmia, which is the loss of smell and can impair flavour perception.

Can ageusia be treated?

Treatment for ageusia depends heavily on the cause. Nutritional deficiencies or medication side effects may be reversible by taking supplements or switching to a different medication, respectively. However, nerve or post-viral damage may take longer to recover, and sometimes full recovery is not possible. Either way, supportive measures like good oral hygiene and enhanced food flavours can help.

What should I do if I think I have ageusia?

If you think you have ageusia, you should see your GP or primary care provider. Sharing information about medications, recent illnesses, dental work, or changes in appetite/weight would be very useful in helping identify the cause. After that, your doctor may perform taste tests, examine your mouth and head, and order blood tests or imaging if needed. Early evaluation can help identify treatable causes and improve quality of life.