New study attempts to characterize the long COVID in all its complexity

Many studies have reported persistent effects of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These post-viral complications are now known as long-COVID. However, the rapid onset of the COVID-19 pandemic and the rush to publish potentially useful data has led to a lack of standardization of phenotypic reports, making it difficult to analyze the data and discover the resulting trends. .

In a new meta-study recently published on medRxiv* the preprint server, a large subset of these reports has been organized and categorized, mapping 287 unique clinical outcomes related to long-COVID.

Identify phenotypic abnormalities

The group began by selecting articles relevant to the long COVID, excluding those with acute COVID time points only or which provided insufficient detail. In the selected reports, 287 phenotypic abnormalities represented by specific terms were identified that were associated with the long COVID, many of which were mapped to identical symptoms. For example, the reporting of fatty liver, fatty liver, fatty liver, fatty infiltration of the liver, and fatty liver could be combined into one term. Fatigue was the most frequently reported term, in 45.1% of cases, and nausea the least reported, in only 3.9% of cases, although there was wide variation among all reported symptoms.

SARS-CoV-2 is believed to affect many organs throughout the body, and many symptoms associated with long COVID are organ specific. The group organized symptoms by organ affected, with pulmonary respiratory problems being the most frequently reported at 35.1%, with the term specific symptom being attributed to dyspnea.

Symptoms of sleep disturbance and decreased lung capacity for carbon monoxide diffusion (DLCO) were also well classified, followed by symptoms associated with gastrointestinal symptoms such as fatty liver and diarrhea. Cells in the lungs and gastrointestinal system express high levels of the ACE2 receptor, explaining the more influential impact of SARS-CoV-2 in these organs. Certain brain and nervous system cells also express the ACE2 receptor at high levels on their surface, believed to be the cause of the loss of taste and smell experienced by many people with COVID-19. This symptom (anosmia) has been reported in 12.8% of people with long-term COVID, and other symptoms related to the brain and nervous system have also been heavily reported. These symptoms included: anxiety (22.2%), cognitive impairment (18.6%), depression (21.1%), dysphagia (1%) and myalgia (13.8%).

Some of the symptoms reported were more or less frequent among those who had experienced severe COVID-19 compared to only mildly or asymptomatic individuals, with fatty liver disease being reported more frequently among severe cases, for example.

Standardization of reports

The Human Phenotype Ontology (HPO) is an international organization that defines a standardized vocabulary for disease symptoms, phenotypic abnormalities. As the sometimes complex terms used to describe phenotypic abnormalities by the medical community are often unknown to the layman, the group is considering the potential benefits provided by implementing algorithms that would automatically categorize symptoms based on information provided by patients, based on the system used here. . Additionally, data mining techniques could be used to determine the frequency of complaints of COVID-related symptoms on social media, massively expanding the dataset available.

Standardization of the long COVID reporting methodology used in this study could help improve the treatment and diagnosis of long COVIDs, and the application of machine learning could accelerate the acquisition of useful data using this process.

In order to determine which terms can be reported by an individual that might be better described by an HPO term, anosmia rather than loss of taste, for example, lists need to be made by metadata analysis. Once refined in HPO terms, the data can be better analyzed and categorized by clinicians and researchers, allowing them to better understand the long-term effects of SARS-CoV-2 infection and how they relate to the severity of the disease. disease.

*Important Notice

medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.