Subtypes of Post–COVID-19 Condition: A Review of the Emerging Evidence


Post–COVID-19 condition is a growing health concern and has been associated with more than 200 possible symptoms. The diverse and varied ways the condition presents clinically creates challenges for developing standard diagnostic criteria, and for health systems aiming to provide effective treatment and management supports for people. 
To support health care, decision-makers and clinicians understand the different clinical presentations of the condition, we scanned the evidence base to examine early approaches being used to characterize and describe subtypes of post–COVID-19 condition. Subtypes can be developed with many different disease features and patient factors, but for this report we specifically reviewed potential subtypes based on symptoms and clinical presentation. 
We found that some of the early approaches used to develop subtypes are based on statistical methods that group together patterns of symptoms. These studies are beginning to reveal potential subtypes based on severity of symptoms, type and co-occurrence of symptoms, and symptoms affecting different organ systems. 
Many reported symptoms of post–COVID-19 condition are similar to previously characterized health conditions. In some cases, subtypes of post–COVID-19 may be manifestations of those other conditions. For example, certain subtypes may present with symptoms similar to myalgic encephalomyelitis/chronic fatigue syndrome or pulmonary fibrosis. It is uncertain whether those subtypes share the same or distinct pathophysiology and whether they may benefit from similar treatments. 
Early evidence comparing the variant of infection and its association with potential subtypes of post–COVID-19 condition is emerging, but the findings are currently mixed. Some studies suggest that variants such as Delta and Omicron may result in different clinical presentations, while other studies have not found significant differences. Further research assessing the association between variants and subtypes is likely needed. 
This review provides some implications and considerations for health systems should emerging research further characterize and validate proposed subtypes. These implications may be important for improving the diagnosis, treatment, and management of post–COVID-19 condition. With estimates in Canada suggesting that more than a million people could be affected by the condition, monitoring ongoing research on subtypes may help support the development of effective and tailored treatments, and guide health systems planning across the country. 
