How is long COVID diagnosed in adults?

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In a recent article published in the Canadian Medical Association Journal, researchers enlisted important points concerning post-coronavirus disease 2019 (COVID-19) or long COVID diagnosis among adults.

Study: Open Access Diagnosing post-COVID-19 condition (long COVID) in adults. Image Credit: Josie Elias/Shutterstock
Study: Open Access Diagnosing post-COVID-19 condition (long COVID) in adults. Image Credit: Josie Elias/Shutterstock


In the present article, researchers listed down essential points concerning long COVID diagnosis among adult individuals, pertaining to the long COVID definition, the prevalence in Canada, systemic nature, clinical presentation, symptom persistence, and associated impact on daily activities among affected individuals.

What is long COVID?

The WHO (World Health Organization) members have proposed a definition of long COVID based on the Delphi technique for group consensus, involving individuals who reported lived experiences and clinical practitioners. The post-COVID-19 or long COVID definition includes individuals with persistent COVID-19 symptoms lingering even after three months of suspected or confirmed COVID-19, lasting for a minimum of two months. Any alternate diagnosis cannot elucidate these symptoms. However, the specificity, sensitivity, negative predictive value, and positive predictive values for the definite long COVID diagnosis criteria need to be ascertained.

Long COVID prevalence in Canada

Long COVID has affected nearly 1.40 million Canadian residents. According to the Canadian coronavirus disease 2019 antibody and health survey of 2022, approximately 15.0% of adult Canadians with probable or confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections reported COVID-19 symptoms experienced after three months of the acute COVID-19 period.

Women (18.0%) showed a greater likelihood compared to men (12.0%) of reporting persistent symptoms. According to a systematic review and meta-analysis of initial COVID-19 experiences with increasingly severe SARS-CoV-2 variants, published in 2022, the worldwide prevalence of COVID-19 is 43.0 percent.

Moreover, the post-COVID-19 condition was reportedly more prevalent among hospitalized individuals (54.0%) than individuals with no COVID-19-associated hospitalizations (34.0%). Consequently, the current long COVID prevalence might be considerably lower due to the increased rates of COVID-19 vaccinations, evolving therapeutic options, and the emergence of SARS-CoV-2 variants with lesser virulence, causing SARS-CoV-2 infections of lesser severity than before.

Systemic nature of long COVID

The systemic nature of long COVID might be in relation to the presence of ACE2 (angiotensin-converting-enzyme 2) receptors, which are critical for SARS-CoV-2 entry into host cells in multiple organs of the human body. Various pathophysiological pathways have been reported to contribute differentially to the development of long COVID, including cell injury, sustained inflammation and viremia, pro-coagulation states, and autoimmunity.

Clinical presentation of long COVID

Studies have reported that long COVID considerably impacts the functioning and health of affected individuals. The condition can present a wide range of >100.0 symptoms and is more commonly observed among females. The most frequently observed and probably modifiable long COVID symptoms are fatigue, depression/anxiety, dyspnea, sleep difficulties, and palpitations, reported among 23% to 63% of individuals, 23% to 46% of individuals, 11% to 43% of individuals, 11% to 31% of individuals, and 6.0% to 22% of individuals affected by long COVID, respectively.

Symptom persistence in long COVID

Many individuals recover from post-COVID-19 conditions; however, the symptoms may persist among a few individuals, who may not be able to resume full-time jobs even after a year of SARS-CoV-2 infection. In a cohort of 1,1192 individuals longitudinally assessed in the year 2022 who were hospitalized in the Wuhan city of China but survived SARS-CoV-2 infections, 68.0% of individuals experienced a minimum of one symptom after six months of the acute COVID-19 period that reduced to 55.0% within two years.

Among the participants, 21.0% of priorly employed individuals did not resume work, and 21.0% of Canadian residents documented that the persistent symptoms always or often posed limitations in the performance of routine activities.


To summarize, based on the above findings, long COVID refers to a condition characterized by the persistence of COVID-19 symptoms beyond three months of the acute COVID-19 period, lasting at least two months, which cannot be attributed to any other diagnosis. The condition has affected many individuals, especially women, and is more commonly observed among hospitalized COVID-19 patients. However, the prevalence may have reduced due to COVID-19 vaccinations, therapeutic drug development, and the circulation of less virulent SARS-CoV-2 variants.

The condition has multi-organ involvement due to the presence of ACE2 receptors in several organs of the human body, to which SARS-CoV-2 binds for host cell invasion. Long COVID symptomatology and pathophysiological mechanisms are diverse, the most common symptoms being dyspnea, depression/anxiety, fatigue, palpitations, and sleep difficulties.

Symptoms may persist for several months or even years post-acute COVID-19, limiting work performance and routine activities.

Journal reference:
Pooja Toshniwal Paharia

Written by

Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.


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