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

Abstract


 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.

Serological markers and long COVID—A rapid systematic review

“…Key strengths of this review include the large volume of reports assessed for eligibility, and careful consideration and thorough description of a wide array of factors which limit inter‐study comparability. Also, we reported findings among different long COVID subtypes, currently an important and growing area of research interest 83 . However, several limitations warrant consideration.…”

“…The exploration of long COVID subtypes is an important and emerging topic, with potential to advance our understanding of pathophysiological mechanisms and markers, and better enable health systems to identify and address key care needs 6,82 . However, there continues to be poor consensus on what these subtypes are, and how clinical characteristics and COVID‐19 variants may influence the manifestation and severity of different symptom patterns 6,33,83,84 . More reports on subtypes and potential biomarkers may yield new findings which illuminate long COVID aetiology, detection and treatment.…”

Serological markers and Post COVID-19 Condition (PCC) – A rapid review of the evidence

“…Key strengths of this review include the large volume of reports assessed for eligibility, and careful consideration and thorough description of a wide array of factors which limit inter-study comparability. Also, we reported findings among different PCC subtypes, currently an important and growing area of research interest [85]. However, several limitations warrant consideration.…”

“…The exploration of PCC subtypes is an important and emerging topic, with potential to advance our understanding of pathophysiological mechanisms and markers, and better enable health systems to identify and address key care needs [6,84]. However, there continues to be poor consensus on what these subtypes are, and how clinical characteristics and COVID-19 variants may influence the manifestation and severity of different symptom patterns [6,33,85,86]. More reports on subtypes and potential biomarkers may yield new findings which illuminate PCC etiology, detection, and treatment.…”

Clinical and Serological Predictors of Post Covid-19 Condition – Findings From a Canadian Prospective Cohort Study

“…Fifth, study sample size also limited opportunity to assess for differences in serological response as a function of PCC subtypes. There is poor consensus on how subtypes of PCC character and severity should be defined [64]. We used self-reported quality of life due to persistent symptoms as a proxy of PCC severity.…”