Biomarkers in long COVID-19: A systematic review

Translating insights into therapies for Long Covid

Long Covid is defined by a wide range of symptoms that persist after the acute phase of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Commonly reported symptoms include fatigue, weakness, postexertional malaise, and cognitive dysfunction, with many other symptoms reported. Symptom range, duration, and severity are highly variable and partially overlap with symptoms of myalgic encephalomyelitis/chronic fatigue syndrome and other post-acute infectious syndromes, highlighting opportunities to define shared mechanisms of pathogenesis. Potential mechanisms of Long Covid are diverse, including persistence of viral reservoirs, dysregulated immune responses, direct viral damage of tissues targeted by SARS-CoV-2, inflammation driven by reactivation of latent viral infections, vascular endothelium activation or dysfunction, and subsequent thromboinflammation, autoimmunity, metabolic derangements, microglial activation, and microbiota dysbiosis. The heterogeneity of symptoms and baseline characteristics of people with Long Covid, as well as the varying states of immunity and therapies given at the time of acute infection, have made etiologies of Long Covid difficult to determine. Here, we examine progress on preclinical models for Long Covid and review progress being made in clinical trials, highlighting the need for large human studies and further development of models to better understand Long Covid. Such studies will inform clinical trials that will define treatments to benefit those living with this condition.

Micronutrients, Vitamin D, and Inflammatory Biomarkers in COVID-19: A Systematic Review and Meta-analysis of Causal Inference Studies

CONTEXT

Experimental and observational studies suggest that circulating micronutrients, including vitamin D (VD), may increase COVID-19 risk and its associated outcomes. Mendelian randomization (MR) studies provide valuable insight into the causal relationship between an exposure and disease outcomes.

OBJECTIVES

The aim was to conduct a systematic review and meta-analysis of causal inference studies that apply MR approaches to assess the role of these micronutrients, particularly VD, in COVID-19 risk, infection severity, and related inflammatory markers.

DATA SOURCES

Searches (up to July 2023) were conducted in 4 databases.

DATA EXTRACTION AND ANALYSIS

The quality of the studies was evaluated based on the MR-STROBE guidelines. Random-effects meta-analyses were conducted where possible.

RESULTS

There were 28 studies (2 overlapped) including 12 on micronutrients (8 on VD) and COVID-19, 4 on micronutrients (all on VD) and inflammation, and 12 on inflammatory markers and COVID-19. Some of these studies reported significant causal associations between VD or other micronutrients (vitamin C, vitamin B6, iron, zinc, copper, selenium, and magnesium) and COVID-19 outcomes. Associations in terms of causality were also nonsignificant with regard to inflammation-related markers, except for VD levels below 25 nmol/L and C-reactive protein (CRP). Some studies reported causal associations between cytokines, angiotensin-converting enzyme 2 (ACE2), and other inflammatory markers and COVID-19. Pooled MR estimates showed that VD was not significantly associated with COVID-19 outcomes, whereas ACE2 increased COVID-19 risk (MR odds ratio = 1.10; 95% CI: 1.01-1.19) but did not affect hospitalization or severity of the disease. The methodological quality of the studies was high in 13 studies, despite the majority (n = 24) utilizing 2-sample MR and evaluated pleiotropy.

CONCLUSION

MR studies exhibited diversity in their approaches but do not support a causal link between VD/micronutrients and COVID-19 outcomes. Whether inflammation mediates the VD-COVID-19 relationship remains uncertain, and highlights the need to address this aspect in future MR studies exploring micronutrient associations with COVID-19 outcomes.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42022328224.

The Importance of Including Long COVID Outcomes When Developing Novel Treatments for Acute COVID-19

Amid efforts to develop effective treatments for acute COVID-19, there is growing recognition of the need to address long COVID as a key outcome measure. We argue there are 7 compelling reasons to include long COVID measurements in clincal trials investigating acute COVID-19 treatments: (1) Long COVID is not rare. (2) Long COVID is debilitating to individuals and has a high societal cost. (3) Those at high risk of severe COVID-19 are also at higher risk of developing long COVID if they are infected with COVID-19. (4) Treatments for acute COVID-19 may reduce the risk of long COVID. (5) Measures exist to track long COVID. (6) Long COVID considerations are potentially important for acute COVID-19 treatment decision making. (7) Deaths and hospitalizations due to COVID-19 are increasingly rare. While not every trial needs to include assessments of long COVID, it is worth the research burden to include assessments where possible, as this could facilitate the uptake of acute COVID-19 treatments that lessen the societal burden of long COVID.

Designing and optimizing clinical trials for long COVID

Long COVID is a debilitating, multisystemic illness following a SARS-CoV-2 infection whose duration may be indefinite. Over four years into the pandemic, little knowledge has been generated from clinical trials. We analyzed the information available on ClinicalTrials.gov, and found that the rigor and focus of trials vary widely, and that the majority test non-pharmacological interventions with insufficient evidence. We highlight promising trials underway, and encourage the proliferation of clinical trials for treating Long COVID and other infection-associated chronic conditions and illnesses (IACCIs). We recommend several guidelines for Long COVID trials: First, pharmaceutical trials with potentially curative, primary interventions should be prioritized, and both drug repurposing and new drug development should be pursued. Second, study designs should be both rigorous and accessible, e.g., triple-blinded randomized trials that can be conducted remotely, without participants needing to leave their homes. Third, studies should have multiple illness comparator cohorts for IACCIs such as myalgic encephalomyelitis (ME/CFS) and dysautonomia, and screen for the full spectrum of symptomatology and pathologies of these illnesses. Fourth, studies should consider inclusion/exclusion criteria with an eye towards equity and breadth of representation, including participants of all races, ethnicities, and genders most impacted by COVID-19, and including all levels of illness severity. Fifth, involving patient-researchers in all aspects of studies brings immensely valuable perspectives that will increase the impact of trials. We also encourage the development of efficient clinical trial designs including methods to study several therapies in parallel.

Unveiling Post-COVID-19 syndrome: incidence, biomarkers, and clinical phenotypes in a Thai population

BACKGROUND

Post-COVID- 19 syndrome (PCS) significantly impacts the quality of life of survivors. There is, however, a lack of a standardized approach to PCS diagnosis and management. Our bidirectional cohort study aimed to estimate PCS incidence, identify risk factors and biomarkers, and classify clinical phenotypes for enhanced management to improve patient outcomes.

METHODS

A bidirectional prospective cohort study was conducted at five medical sites in Hatyai district in Songkhla Province, Thailand. Participants were randomly selected from among the survivors of COVID-19 aged≥18 years between May 15, 2022, and January 31, 2023. The selected participants underwent a scheduled outpatient visit for symptom and health assessments 12 to 16 weeks after the acute onset of infection, during which PCS was diagnosed and blood samples were collected for hematological, inflammatory, and serological tests. PCS was defined according to the World Health Organization criteria. Univariate and multiple logistic regression analyses were used to identify biomarkers associated with PCS. Moreover, three clustering methods (agglomerative hierarchical, divisive hierarchical, and K-means clustering) were applied, and internal validation metrics were used to determine clustering and similarities in phenotypes.

FINDINGS

A total of 300 survivors were enrolled in the study, 47% of whom developed PCS according to the World Health Organization (WHO) definition. In the sampled cohort, 66.3% were females, and 79.4% of them developed PCS (as compared to 54.7% of males, p-value <0.001). Comorbidities were present in 19% (57/300) of all patients, with 11% (18/159) in the group without PCS and 27.7% (39/141) in the group with PCS. The incidence of PCS varied depending on the criteria used and reached 13% when a quality of life indicator was added to the WHO definition. Common PCS symptoms were hair loss (22%) and fatigue (21%), while mental health symptoms were less frequent (insomnia 3%, depression 3%, anxiety 2%). According to our univariate analysis, we found significantly lower hematocrit and IgG levels and greater ALP levels in PCS patients than in patients who did not develop PCS (p-value < 0.05). According to our multivariable analysis, adjusted ALP levels remained a significant predictor of PCS (OR 1.02, p-value= 0.005). Clustering analysis revealed four groups characterized by severe clinical symptoms and mental health concerns (Cluster 1, 4%), moderate physical symptoms with predominant mental health issues (Cluster 2, 9%), moderate mental health issues with predominant physical symptoms (Cluster 3, 14%), and mild to no PCS (Cluster 4, 77%). The quality of life and ALP levels varied across the clusters.

INTERPRETATION

This study challenges the prevailing diagnostic criteria for PCS, emphasizing the need for a holistic approach that considers quality of life. The identification of ALP as a biomarker associated with PCS suggests that its monitoring could be used for early detection of the onset of PCS. Cluster analysis revealed four distinct clinical phenotypes characterized by different clinical symptoms and mental health concerns that 'exhibited varying impacts on quality of life. This finding suggested that accounting for the reduced quality of life in the definition of PCS could enhance its diagnosis and management and that moving toward personalized interventions could both improve patient outcomes and help reduce medicalization and optimally target the available resources.

FUNDING

The research publication received funding support from Medical Council of Thailand (Police General Dr. Jongjate Aojanepong Foundation), Hatyai Hospital Charity and Wellcome Trust.

Effects of an 8-week high-dose vitamin D supplementation on fatigue and neuropsychiatric manifestations in post-COVID syndrome: A randomized controlled trial

AIM

This study evaluated the effectiveness of high-dose vitamin D supplementation in alleviating fatigue and neuropsychiatric symptoms in post-COVID syndrome.

METHODS

In an 8-week, double-blind, randomized, placebo-controlled trial, 80 patients with post-COVID fatigue or neuropsychiatric symptoms were enrolled. Participants were randomly assigned to receive either 60,000 IU of vitamin D weekly (n = 40) or a placebo (n = 40) for 8 weeks. Clinical outcomes were assessed using the 11-item Chalder Fatigue Scale (CFQ-11); 21-item Depression, Anxiety, and Stress Scale (DASS-21); Pittsburgh Sleep Quality Index (PSQI); Addenbrooke's Cognitive Examination III (ACE); and Trail Making Test A and B (TMT-A and TMT-B). Baseline and 8-week measurements of inflammatory markers, including interleukin 6 (IL-6) and C-reactive protein (CRP), were also collected.

RESULTS

Significant improvements were found in the vitamin D group for CFQ (coefficient -3.5, P = 0.024), DASS-anxiety (-2.0, P = 0.011), and ACE (2.1, P = 0.012). No significant differences were observed in PSQI, DASS-depression, TMT, IL-6, or CRP levels. The incidence of adverse events was comparable between groups, with no serious adverse events reported.

CONCLUSION

High-dose vitamin D supplementation may benefit patients with post-COVID syndrome by reducing fatigue, alleviating anxiety, and improving cognitive symptoms, with minimal side effects.

COVID-19 and multiple sclerosis: challenges and lessons for patient care

During the COVID-19 pandemic, people with multiple sclerosis (MS) and their healthcare providers have faced unique challenges related to the interaction between SARS-CoV-2, underlying neurological disease and the use of disease-modifying treatments (DMTs). Key concerns arose, primarily related to the possibility that SARS-CoV-2 infection could trigger the initial demyelinating event or exacerbate disease activity. Another major concern was the safety and efficacy of the COVID-19 vaccines, especially for patients undergoing specific treatments that could weaken their antibody responses. In the post-infection phase, identifying long COVID in patients with MS has been complicated due to the large overlap between post-infection sequelae and MS symptoms. In addition, disruptions in health and rehabilitation services have made it difficult for MS patients to access care. This Series article explores current evidence on the interaction between MS and SARS-CoV-2, identifies the challenges posed by the COVID-19 pandemic in the care of patients with MS, and discusses the significant adoption of digital health solutions, including telemedicine and new technology-based rehabilitation approaches. Based on lessons learned, recommendations and future directions are offered for managing patients with MS, rethinking healthcare systems and improving health outcomes in the post-COVID-19 pandemic era.

Blood Biomarkers of Long COVID: A Systematic Review

BACKGROUND

Long coronavirus disease (COVID; LC) affects millions of people worldwide. The exact mechanisms which result in a broad, undulating and detrimental symptom profile remain unknown. Blood biomarkers associated with LC have been described; however, consensus on these remains elusive, in part due to a lack of continuity between studies on a universally accepted definition of LC. This systematic review aimed to consolidate current knowledge of blood biomarkers associated with the prevalence of LC on the basis of the World Health Organisation (WHO) clinical definition of this condition.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Observational, cross-sectional, and randomised control studies published in the English language that studied blood biomarkers associated with the WHO definition of LC. All studies included participants who were ≥ 18 years old and group sizes ≥ 10 participants, and were compared against a control group without any known co-morbidities.

METHODS

A systematic literature search was conducted according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines and prospectively registered on Prospero (ID: CRD42022373121). The Cochrane, Embase, PubMed and Web of Science databases were searched from inception to January 2024. Search results were gathered using Rayyan software and data extracted using Microsoft Excel. The reporting recommendations for tumour markers prognostic studies (REMARK) questionnaire was used to assess the quality of the included studies.

RESULTS

A total of 45 observational and one interventional study comprising 4415 participants were included in this review which identified 525 blood biomarkers thought to be associated with LC. Three blood biomarker subtypes were associated with the development of LC: (1) immunological and inflammatory dysfunction, (2) endothelial/vascular dysfunction and (3) metabolic and clotting abnormalities.

DISCUSSION AND CONCLUSIONS

Our data are consistent with previous findings; however, no single biomarker was sufficiently associated with LC prevalence and instead a profile of biomarkers across various physiological systems may be more clinically useful. In all, 196 studies were excluded due to a lack of an adequately healthy comparator group and/or failure to meet the WHO LC definition. This demonstrates a need for further research incorporating a universal LC definition across all disease severity groups and symptom profiles, and longitudinal data reflecting the relapsing and remitting nature of this condition. Further investigation into blood biomarkers of LC, including clear reporting of healthy comparator groups and the investigation of acute and chronic biomarker changes, within the context of medical practice, may support the development of curative/restorative approaches.

Differentiation of Prior SARS-CoV-2 Infection and Postacute Sequelae by Standard Clinical Laboratory Measurements in the RECOVER Cohort

BACKGROUND

There are currently no validated clinical biomarkers of postacute sequelae of SARS-CoV-2 infection (PASC).

OBJECTIVE

To investigate clinical laboratory markers of SARS-CoV-2 and PASC.

DESIGN

Propensity score-weighted linear regression models were fitted to evaluate differences in mean laboratory measures by prior infection and PASC index (≥12 vs. 0). (ClinicalTrials.gov: NCT05172024).

SETTING

83 enrolling sites.

PARTICIPANTS

RECOVER-Adult cohort participants with or without SARS-CoV-2 infection with a study visit and laboratory measures 6 months after the index date (or at enrollment if >6 months after the index date). Participants were excluded if the 6-month visit occurred within 30 days of reinfection.

MEASUREMENTS

Participants completed questionnaires and standard clinical laboratory tests.

RESULTS

Among 10 094 participants, 8746 had prior SARS-CoV-2 infection, 1348 were uninfected, 1880 had a PASC index of 12 or higher, and 3351 had a PASC index of zero. After propensity score adjustment, participants with prior infection had a lower mean platelet count (265.9 × 109 cells/L [95% CI, 264.5 to 267.4 × 109 cells/L]) than participants without known prior infection (275.2 × 109 cells/L [CI, 268.5 to 282.0 × 109 cells/L]), as well as higher mean hemoglobin A1c (HbA1c) level (5.58% [CI, 5.56% to 5.60%] vs. 5.46% [CI, 5.40% to 5.51%]) and urinary albumin-creatinine ratio (81.9 mg/g [CI, 67.5 to 96.2 mg/g] vs. 43.0 mg/g [CI, 25.4 to 60.6 mg/g]), although differences were of modest clinical significance. The difference in HbA1c levels was attenuated after participants with preexisting diabetes were excluded. Among participants with prior infection, no meaningful differences in mean laboratory values were found between those with a PASC index of 12 or higher and those with a PASC index of zero.

LIMITATION

Whether differences in laboratory markers represent consequences of or risk factors for SARS-CoV-2 infection could not be determined.

CONCLUSION

Overall, no evidence was found that any of the 25 routine clinical laboratory values assessed in this study could serve as a clinically useful biomarker of PASC.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Cardiovascular abnormalities of long-COVID syndrome: Pathogenic basis and potential strategy for treatment and rehabilitation

Cardiac injury and sustained cardiovascular abnormalities in long-COVID syndrome, i.e. post-acute sequelae of coronavirus disease 2019 (COVID-19) have emerged as a debilitating health burden that has posed challenges for management of pre-existing cardiovascular conditions and other associated chronic comorbidities in the most vulnerable group of patients recovered from acute COVID-19. A clear and evidence-based guideline for treating cardiac issues of long-COVID syndrome is still lacking. In this review, we have summarized the common cardiac symptoms reported in the months after acute COVID-19 illness and further evaluated the possible pathogenic factors underlying the pathophysiology process of long-COVID. The mechanistic understanding of how Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) damages the heart and vasculatures is critical in developing targeted therapy and preventive measures for limiting the viral attacks. Despite the currently available therapeutic interventions, a considerable portion of patients recovered from severe COVID-19 have reported a reduced functional reserve due to deconditioning. Therefore, a rigorous and comprehensive cardiac rehabilitation program with individualized exercise protocols would be instrumental for the patients with long-COVID to regain the physical fitness levels comparable to their pre-illness baseline.

Long COVID: a clinical update

Post-COVID-19 condition (also known as long COVID) is generally defined as symptoms persisting for 3 months or more after acute COVID-19. Long COVID can affect multiple organ systems and lead to severe and protracted impairment of function as a result of organ damage. The burden of this disease, both on the individual and on health systems and national economies, is high. In this interdisciplinary Review, with a coauthor with lived experience of severe long COVID, we sought to bring together multiple streams of literature on the epidemiology, pathophysiology (including the hypothesised mechanisms of organ damage), lived experience and clinical manifestations, and clinical investigation and management of long COVID. Although current approaches to long COVID care are largely symptomatic and supportive, recent advances in clinical phenotyping, deep molecular profiling, and biomarker identification might herald a more mechanism-informed and personally tailored approach to clinical care. We also cover the organisation of services for long COVID, approaches to preventing long COVID, and suggestions for future research.

A Disease Hidden in Plain Sight: Pathways and Mechanisms of Neurological Complications of Post-acute Sequelae of COVID-19 (NC-PASC)

The global impact of coronavirus disease 2019 (COVID-19) marked by numerous pandemic peaks is attributed to its high variability and infectious nature, transforming it into a persistent global public health concern. With hundreds of millions of cases reported globally, the illness is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite its initial classification as an acute respiratory illness, recent evidence indicates that lingering effects on various bodily systems, such as cardiovascular, pulmonary, nervous, gastrointestinal (GI), and musculoskeletal, may endure well beyond the acute phase. These persistent manifestations following COVID-19, commonly known as long COVID, have the potential to affect individuals across the entire range of illness severity, with a tendency to be more prevalent in mild to moderate cases. At present, there are no established criteria for diagnosing long COVID. Nonetheless, it is conceptualized as a multi-organ disorder encompassing a diverse array of clinical manifestations. The most common, persistent, and debilitating symptoms of long COVID may be neurological, known as neurological complications of post-acute sequelae of COVID-19 (NC-PASC). More than one-third of individuals with a prior SARS-CoV-2 infection show involvement of both the central nervous system (CNS) and peripheral nervous system (PNS), as evidenced by an approximately threefold higher incidence of neurological symptoms in observational studies. The persistent neurological symptoms of long COVID encompass fatigue, headache, cognitive decline, "brain fog", dysautonomia, neuropsychiatric issues, loss of smell (anosmia), loss of taste (ageusia), and peripheral nerve problems (peripheral neuropathy). Reported pathogenic mechanisms encompass viral persistence and neuro-invasion by SARS-CoV-2, neuroinflammation, autoimmunity, coagulopathy, and endotheliopathy. Raising awareness of potential complications is crucial for preventing and alleviating the long-term effects of long COVID and enhancing the prognosis for affected patients. This review explores the hypothetical pathophysiological mechanisms and pathways of NC-PASC with a sole aim to increase awareness about this crippling disease.

Long COVID science, research and policy

Long COVID represents the constellation of post-acute and long-term health effects caused by SARS-CoV-2 infection; it is a complex, multisystem disorder that can affect nearly every organ system and can be severely disabling. The cumulative global incidence of long COVID is around 400 million individuals, which is estimated to have an annual economic impact of approximately $1 trillion-equivalent to about 1% of the global economy. Several mechanistic pathways are implicated in long COVID, including viral persistence, immune dysregulation, mitochondrial dysfunction, complement dysregulation, endothelial inflammation and microbiome dysbiosis. Long COVID can have devastating impacts on individual lives and, due to its complexity and prevalence, it also has major ramifications for health systems and economies, even threatening progress toward achieving the Sustainable Development Goals. Addressing the challenge of long COVID requires an ambitious and coordinated-but so far absent-global research and policy response strategy. In this interdisciplinary review, we provide a synthesis of the state of scientific evidence on long COVID, assess the impacts of long COVID on human health, health systems, the economy and global health metrics, and provide a forward-looking research and policy roadmap.

Unraveling the enigma of long COVID: novel aspects in pathogenesis, diagnosis, and treatment protocols

Long COVID, now unmistakably identified as a syndromic entity encompassing a complex spectrum of symptoms, demands immediate resolution of its elusive pathogenic underpinnings. The intricate interplay of diverse factors presents a complex puzzle, difficult to resolve, and thus poses a substantial challenge. As instances of long COVID manifest by repeated infections of SARS-CoV-2 and genetic predisposition, a detailed understanding in this regard is needed. This endeavor is a comprehensive exploration and analysis of the cascading pathogenetic events driven by viral persistence and replication. Beyond its morbidity, long COVID, more disabling than fatal, exacts one of the most substantial tolls on public health in contemporary times, with the potential to cripple national economies. The paper introduces a unified theory of long COVID, detailing a novel pathophysiological framework that interlinks persistent SARS-CoV-2 infection, autoimmunity, and systemic vascular pathology. We posit a model where viral reservoirs, immune dysregulation, and genetic predispositions converge to perpetuate disease. It challenges prevailing hypotheses with new evidence, suggesting innovative diagnostic and therapeutic approaches. The paper aims to shift the paradigm in long COVID research by providing an integrative perspective that encapsulates the multifaceted nature of the condition. We explain the immunological mechanisms, hypercoagulability states, and viral reservoirs in the skull that feed NeuroCOVID in patients with long COVID. Also, this study hints toward a patient approach and how to prioritize treatment sequences in long COVID patients in hospitals and clinics.

COVID-19 and Long COVID: Disruption of the Neurovascular Unit, Blood-Brain Barrier, and Tight Junctions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), could affect brain structure and function. SARS-CoV-2 can enter the brain through different routes, including the olfactory, trigeminal, and vagus nerves, and through blood and immunocytes. SARS-CoV-2 may also enter the brain from the peripheral blood through a disrupted blood-brain barrier (BBB). The neurovascular unit in the brain, composed of neurons, astrocytes, endothelial cells, and pericytes, protects brain parenchyma by regulating the entry of substances from the blood. The endothelial cells, pericytes, and astrocytes highly express angiotensin converting enzyme 2 (ACE2), indicating that the BBB can be disturbed by SARS-CoV-2 and lead to derangements of tight junction and adherens junction proteins. This leads to increased BBB permeability, leakage of blood components, and movement of immune cells into the brain parenchyma. SARS-CoV-2 may also cross microvascular endothelial cells through an ACE2 receptor-associated pathway. The exact mechanism of BBB dysregulation in COVID-19/neuro-COVID is not clearly known, nor is the development of long COVID. Various blood biomarkers could indicate disease severity and neurologic complications in COVID-19 and help objectively diagnose those developing long COVID. This review highlights the importance of neurovascular and BBB disruption, as well as some potentially useful biomarkers in COVID-19, and long COVID/neuro-COVID.

Definitions and symptoms of the post-COVID syndrome: an updated systematic umbrella review

Post-COVID syndrome (PCS) describes a persistent complex of symptoms following a COVID-19 episode, lasting at least 4 to 12 weeks, depending on the specific criteria used for its definition. It is often associated with moderate to severe impairments of daily life and represents a major burden for many people worldwide. However, especially during the first two years of the COVID-19 pandemic, therapeutic and diagnostic uncertainties were prominent due to the novelty of the disease and non-specific definitions that overlooked functional deficits and lacked objective assessment. The present work comprehensively examines the status of PCS definitions as depicted in recent reviews and meta-analyses, alongside exploring associated symptoms and functional impairments. We searched the database Pubmed for reviews and meta-analysis evaluating PCS in the period between May 31, 2022, to December 31, 2023. Out of 95 studies, 33 were selected for inclusion in our analyses. Furthermore, we extended upon prior research by systematically recording the symptoms linked with PCS as identified in the studies. We found that fatigue, neurological complaints, and exercise intolerance were the most frequently reported symptoms. In conclusion, over the past eighteen months, there has been a notable increase in quantity and quality of research studies on PCS. However, there still remains a clear need for improvement, particularly with regard to the definition of the symptoms necessary for diagnosing this syndrome. Enhancing this aspect will render future research more comparable and precise, thereby advancing and understanding PCS.

Addressing Post-Acute COVID-19 Syndrome in Cancer Patients, from Visceral Obesity and Myosteatosis to Systemic Inflammation: Implications in Cardio-Onco-Metabolism

Cardiovascular disease and cancer are the two leading causes of morbidity and mortality in the world. The emerging field of cardio-oncology described several shared risk factors that predispose patients to both cardiovascular disease and cancer. Post-acute COVID-19 syndrome is a chronic condition that occurs in many patients who have experienced a SARS-CoV-2 infection, mainly based on chronic fatigue, sedentary lifestyle, cramps, breathing difficulties, and reduced lung performance. Post-acute COVID-19 exposes patients to increased visceral adiposity, insulin resistance, myosteatosis, and white adipose tissue content (surrounded by M1 macrophages and characterized by a Th1/Th17 phenotype), which increases the risk of cardiovascular mortality and cancer recurrence. In this review, the main metabolic affections of post-acute COVID-19 syndrome in cancer patients at low and high risk of cardiomyopathies will be summarized. Furthermore, several non-pharmacological strategies aimed at reducing atherosclerotic and cardiac risk will be provided, especially through anti-inflammatory nutrition with a low insulin and glycemic index, appropriate physical activity, and immune-modulating bioactivities able to reduce visceral obesity and myosteatosis, improving insulin-related signaling and myocardial metabolism.

Clinical characteristics, anti-SARS-CoV-2 IgG titers, and inflammatory markers in individuals with post-COVID-19 condition in Kenya: a cross-sectional study

Background

Post-coronavirus disease 2019 (post-COVID-19) is associated with considerable morbidity and reduced quality of life. However, studies characterizing the post-COVID-19 condition in Kenya are limited. This study aimed to determine the prevalence of post-COVID-19 condition and determine the clinical characteristics, anti-SARS-CoV-2 IgG titers, and concentrations of inflammatory markers of individuals with post-COVID-19 condition in Kenya.

Methods

This descriptive cross-sectional study was conducted at the Kenyatta University Health Unit, Kenya. Demographic and clinical data were collected using a questionnaire. The serum levels of anti-SARS-CoV-2 antibodies, interleukin 6 (IL-6), and C-reactive protein (CRP) were quantified by enzyme-linked immunosorbent assays. Independent samples t-test was used to compare the anti-SARS-CoV-2 IgG, IL-6, and CRP levels between the participants with and without post-COVID-19 symptoms. The case definition for post-COVID-19 condition was persistence of acute COVID-19 symptoms or emergence of new symptoms 3 months after COVID-19 diagnosis, symptoms lasting for ≥2 months, and absence of any other etiological basis to explain the symptoms.

Results

A total of 189 volunteers were recruited in this study (median age: 21 years, range: 18-71 years; male, 49.2%). Forty participants reported having had at least one COVID-19 positive diagnosis in the past, of which 12 (30%) complained of post-COVID-19 symptoms. Significant differences in the number and duration of symptoms were observed between the individuals with and without post-COVID-19 symptoms (t-statistic = 2.87, p = 0.01; t-statistic = 2.39, p = 0.02, respectively). However, no significant differences in serum levels of anti-SARS-CoV-2 IgG, IL-6, and CRP were observed between the two groups (P = 0.08, 0.9, and 0.28, respectively).

Conclusion

These findings suggest that post-COVID-19 condition is a health concern even for a relatively young population in Kenya and globally. This condition requires more attention and well-designed studies to better define it and identify clinical chemistry markers that can be used for its diagnosis.

A pilot randomized controlled trial of major ozone autohemotherapy for patients with post-acute sequelae of COVID-19

This prospective, randomized, controlled clinical trial assessed the therapeutic effects of major ozone autohemotherapy (O3-MAH) in patients with post-acute sequelae of COVID-19 (PASC). Seventy-three eligible participants were randomly assigned to an O3-MAH plus conventional therapy group (n = 35) or a conventional therapy alone group (n = 38). Symptom score, pulmonary function, 6-minute walk distance (6MWD), and hematological, biochemical, and immunological parameters were evaluated before and after the interventions. Both groups demonstrated improvements in various parameters post-intervention, but efficacy was greater in the O3-MAH group than the conventional treatment group; with intervention effectiveness defined as a ≥ 50 % reduction in symptom score, 25 of 35 patients (71 %) responded to O3-MAH, while 17/38 patients (45 %) responded to conventional treatment alone (P = 0.0325). Significant improvements in symptom scores (P = 0.0478), tidal volume (P = 0.0374), predicted 6MWD (P = 0.0032), and coagulation and inflammatory indicators were noted in the O3-MAH group compared with the conventional treatment group. O3-MAH was more likely to be effective in patients with elevated CRP levels. Furthermore, O3-MAH markedly improved cellular immunity, and this improvement became more pronounced with extended treatment duration. In summary, combining O3-MAH with conventional treatment was more effective than conventional therapy alone in improving symptoms, pulmonary function, inflammation, coagulation, and cellular immunity in patients with PASC. Further research is now warranted to validate these findings and individualize the regimen.

Insights from an N3C RECOVER EHR-based cohort study characterizing SARS-CoV-2 reinfections and Long COVID

BACKGROUND

Although the COVID-19 pandemic has persisted for over 3 years, reinfections with SARS-CoV-2 are not well understood. We aim to characterize reinfection, understand development of Long COVID after reinfection, and compare severity of reinfection with initial infection.

METHODS

We use an electronic health record study cohort of over 3 million patients from the National COVID Cohort Collaborative as part of the NIH Researching COVID to Enhance Recovery Initiative. We calculate summary statistics, effect sizes, and Kaplan-Meier curves to better understand COVID-19 reinfections.

RESULTS

Here we validate previous findings of reinfection incidence (6.9%), the occurrence of most reinfections during the Omicron epoch, and evidence of multiple reinfections. We present findings that the proportion of Long COVID diagnoses is higher following initial infection than reinfection for infections in the same epoch. We report lower albumin levels leading up to reinfection and a statistically significant association of severity between initial infection and reinfection (chi-squared value: 25,697, p-value: <0.0001) with a medium effect size (Cramer's V: 0.20, DoF = 3). Individuals who experienced severe initial and first reinfection were older in age and at a higher mortality risk than those who had mild initial infection and reinfection.

CONCLUSIONS

In a large patient cohort, we find that the severity of reinfection appears to be associated with the severity of initial infection and that Long COVID diagnoses appear to occur more often following initial infection than reinfection in the same epoch. Future research may build on these findings to better understand COVID-19 reinfections.

Assessing the Potential of an Enzymatically Liberated Salmon Oil to Support Immune Health Recovery from Acute SARS-CoV-2 Infection via Change in the Expression of Cytokine, Chemokine and Interferon-Related Genes

Cytokines, chemokines, and interferons are released in response to viral infection with the ultimate aim of viral clearance. However, in SARS-CoV-2 infection, there is an imbalanced immune response, with raised cytokine levels but only a limited interferon response with inefficient viral clearance. Furthermore, the inflammatory response can be exaggerated, which risks both acute and chronic sequelae. Several observational studies have suggested a reduced risk of progression to severe COVID-19 in subjects with a higher omega-3 index. However, randomized studies of omega-3 supplementation have failed to replicate this benefit. Omega-3 fats provide important anti-inflammatory effects; however, fatty fish contains many other fatty acids that provide health benefits distinct from omega-3. Therefore, the immune health benefit of whole salmon oil (SO) was assessed in adults with mild to moderate COVID-19. Eleven subjects were randomized to best supportive care (BSC) with or without a full spectrum, enzymatically liberated SO, dosed at 4g daily, for twenty-eight days. Nasal swabs were taken to measure the change in gene expression of markers of immune response and showed that the SO provided both broad inflammation-resolving effects and improved interferon response. The results also suggest improved lung barrier function and enhanced immune memory, although the clinical relevance needs to be assessed in longer-duration studies. In conclusion, the salmon oil was well tolerated and provided broad inflammation-resolving effects, indicating a potential to enhance immune health.

BASOPHILS ACTIVATE PRURICEPTOR-LIKE VAGAL SENSORY NEURONS

Vagal sensory neurons convey sensations from internal organs along the vagus nerve to the brainstem. Pruriceptors are a subtype of neurons that transmit itch and induce pruritus. Despite extensive research on the molecular mechanisms of itch, studies focusing on pruriceptors in the vagal ganglia still need to be explored. In this study, we characterized vagal pruriceptor neurons by their responsiveness to pruritogens such as lysophosphatidic acid, β-alanine, chloroquine, and the cytokine oncostatin M. We discovered that lung-resident basophils produce oncostatin M and that its release can be induced by engagement of FcεRIα. Oncostatin M then sensitizes multiple populations of vagal sensory neurons, including Tac1+ and MrgprA3+ neurons in the jugular ganglia. Finally, we observed an increase in oncostatin M release in mice sensitized to the house dust mite Dermatophagoides pteronyssinus or to the fungal allergen Alternaria alternata, highlighting a novel mechanism through which basophils and vagal sensory neurons may communicate during type I hypersensitivity diseases such as allergic asthma.

Exploring the Pathophysiology of Long COVID: The Central Role of Low-Grade Inflammation and Multisystem Involvement

Long COVID (LC), also referred to as Post COVID-19 Condition, Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), and other terms, represents a complex multisystem disease persisting after the acute phase of COVID-19. Characterized by a myriad of symptoms across different organ systems, LC presents significant diagnostic and management challenges. Central to the disorder is the role of low-grade inflammation, a non-classical inflammatory response that contributes to the chronicity and diversity of symptoms observed. This review explores the pathophysiological underpinnings of LC, emphasizing the importance of low-grade inflammation as a core component. By delineating the pathogenetic relationships and clinical manifestations of LC, this article highlights the necessity for an integrated approach that employs both personalized medicine and standardized protocols aimed at mitigating long-term consequences. The insights gained not only enhance our understanding of LC but also inform the development of therapeutic strategies that could be applicable to other chronic conditions with similar pathophysiological features.

Growth Differentiation Factor-15 Is Considered a Predictive Biomarker of Long COVID in Non-hospitalized Patients

Mitochondrial dysfunction is associated with various diseases. Mitochondria plays a regulatory role during infection. The association between mitokines and subsequent COVID progression has not been previously studied. The retrospective cohort study aimed to investigate the potential of serum mitokines as long COVID biomarkers in non-hospitalized patients. Patients with confirmed SARS-CoV-2 infection and blood test reports between January 2021 and April 2023 were included. Patients were categorized into two groups, the recovered and long COVID groups, based on fatigue, decline in focus, and pain. Serum levels of growth differentiation factor 15 (GDF-15) and fibroblast growth factor-21 (FGF-21), which are affected by mitochondrial function, along with inflammatory and vascular endothelium markers, were measured using enzyme-linked immunosorbent assays (ELISA). A receiver operating characteristic curve was used to screen the biomarkers. The threshold value of GDF-15 in the acute phase was 965 pg/mL (sensitivity: 71.4%, specificity: 83.3%), indicating that GDF-15 may be associated with the presence of symptoms three months post onset. No association with inflammatory markers and vascular structures was observed. Therefore, elevated GDF-15 levels in the acute phase may act as a predictive biomarker of long COVID.

SARS-CoV-2 induces blood-brain barrier and choroid plexus barrier impairments and vascular inflammation in mice

The coronavirus disease of 2019 (COVID-19) pandemic has led to more than 700 million confirmed cases and nearly 7 million deaths. Although severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus mainly infects the respiratory system, neurological complications are widely reported in both acute infection and long-COVID cases. Despite the success of vaccines and antiviral treatments, neuroinvasiveness of SARS-CoV-2 remains an important question, which is also centered on the mystery of whether the virus is capable of breaching the barriers into the central nervous system. By studying the K18-hACE2 infection model, we observed clear evidence of microvascular damage and breakdown of the blood-brain barrier (BBB). Mechanistically, SARS-CoV-2 infection caused pericyte damage, tight junction loss, endothelial activation and vascular inflammation, which together drive microvascular injury and BBB impairment. In addition, the blood-cerebrospinal fluid barrier at the choroid plexus was also impaired after infection. Therefore, cerebrovascular and choroid plexus dysfunctions are important aspects of COVID-19 and may contribute to neurological complications both acutely and in long COVID.

Long-COVID-19 autonomic dysfunction: An integrated view in the framework of inflammaging

The recently identified syndrome known as Long COVID (LC) is characterized by a constellation of debilitating conditions that impair both physical and cognitive functions, thus reducing the quality of life and increasing the risk of developing the most common age-related diseases. These conditions are linked to the presence of symptoms of autonomic dysfunction, in association with low cortisol levels, suggestive of reduced hypothalamic-pituitary-adrenal (HPA) axis activity, and with increased pro-inflammatory condition. Alterations of dopamine and serotonin neurotransmitter levels were also recently observed in LC. Interestingly, at least some of the proposed mechanisms of LC development overlap with mechanisms of Autonomic Nervous System (ANS) imbalance, previously detailed in the framework of the aging process. ANS imbalance is characterized by a proinflammatory sympathetic overdrive, and a concomitant decreased anti-inflammatory vagal parasympathetic activity, associated with reduced anti-inflammatory effects of the HPA axis and cholinergic anti-inflammatory pathway (CAP). These neuro-immune-endocrine system imbalanced activities fuel the vicious circle of chronic inflammation, i.e. inflammaging. Here, we refine our original hypothesis that ANS dysfunction fuels inflammaging and propose that biomarkers of ANS imbalance could also be considered biomarkers of inflammaging, recognized as the main risk factor for developing age-related diseases and the sequelae of viral infections, i.e. LC.

Role of C-reactive protein, IL-6, and D-dimers in prediction of severity of coronavirus disease 2019: A pilot study

Background

The global outbreak of coronavirus disease 2019 (COVID-19) presents numerous obstacles for healthcare professionals. The present study aimed to evaluate and compare the role of serum biomarkers like- C-reactive protein (CRP), interleukin-6 (IL-6), and D-dimers in the severity of COVID-19 infection.

Methodology

A cross-sectional, observational retrospective pilot study was conducted in Udaipur, Rajasthan, wherein data was collected from 250 subjects, out of which, data of 100 subjects were included as per the inclusion criteria. The data was recorded retrospectively among the health professionals via Google Forms in Udaipur, Rajasthan.

Results

There were 1 (1%), 3 (3%), 31 (31%) and 65 (65%) participants with minor elevation (0.3-1.0), moderate elevation (1-10), marked elevation (10-50) and severe elevation (>50) of CRP respectively. The difference between the groups was statistically highly significant with a significantly higher number of study participants with a severe elevation of CRP levels (χ2 = 107.84, P < 0.001). The results showed that there was a significant difference between the groups with IL6 in 0-7 range while 96 (96%) study participants had >7 IL6, and the difference was statistically highly significant (2 = 84.640, P 0.001).

Conclusion

In conclusion, the existing body of research indicates a discernible correlation between COVID-19 infection and the fluctuation of biomarker levels. This supplement has the potential to be utilised in clinical practice as a means of informing treatment decisions and determining the necessity of admission to the intensive care unit (ICU).

Blood Markers Show Neural Consequences of LongCOVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) persists throughout the world with over 65 million registered cases of survivors with post-COVID-19 sequelae, also known as LongCOVID-19 (LongC). LongC survivors exhibit various symptoms that span multiple organ systems, including the nervous system. To search for neurological markers of LongC, we investigated the soluble biomolecules present in the plasma and the proteins associated with plasma neuronal-enriched extracellular vesicles (nEVs) in 33 LongC patients with neurological impairment (nLongC), 12 COVID-19 survivors without any LongC symptoms (Cov), and 28 pre-COVID-19 healthy controls (HC). COVID-19 positive participants were infected between 2020 and 2022, not hospitalized, and were vaccinated or unvaccinated before infection. IL-1β was significantly increased in both nLongC and Cov and IL-8 was elevated in only nLongC. Both brain-derived neurotrophic factor and cortisol were significantly elevated in nLongC and Cov compared to HC. nEVs from people with nLongC had significantly elevated protein markers of neuronal dysfunction, including amyloid beta 42, pTau181 and TDP-43. This study shows chronic peripheral inflammation with increased stress after COVID-19 infection. Additionally, differentially expressed nEV neurodegenerative proteins were identified in people recovering from COVID-19 regardless of persistent symptoms.

Assessment of search strategies in Medline to identify studies on the impact of long COVID on workability

Objectives

Studies on the impact of long COVID on work capacity are increasing but are difficult to locate in bibliographic databases, due to the heterogeneity of the terms used to describe this new condition and its consequences. This study aims to report on the effectiveness of different search strategies to find studies on the impact of long COVID on work participation in PubMed and to create validated search strings.

Methods

We searched PubMed for articles published on Long COVID and including information about work. Relevant articles were identified and their reference lists were screened. Occupational health journals were manually scanned to identify articles that could have been missed. A total of 885 articles potentially relevant were collected and 120 were finally included in a gold standard database. Recall, Precision, and Number Needed to Read (NNR) of various keywords or combinations of keywords were assessed.

Results

Overall, 123 search-words alone or in combination were tested. The highest Recalls with a single MeSH term or textword were 23 and 90%, respectively. Two different search strings were developed, one optimizing Recall while keeping Precision acceptable (Recall 98.3%, Precision 15.9%, NNR 6.3) and one optimizing Precision while keeping Recall acceptable (Recall 90.8%, Precision 26.1%, NNR 3.8).

Conclusions

No single MeSH term allows to find all relevant studies on the impact of long COVID on work ability in PubMed. The use of various MeSH and non-MeSH terms in combination is required to recover such studies without being overwhelmed by irrelevant articles.

SARS-CoV-2's brain impact: revealing cortical and cerebellar differences via cluster analysis in COVID-19 recovered patients

BACKGROUND

COVID-19 is a disease known for its neurological involvement. SARS-CoV-2 infection triggers neuroinflammation, which could significantly contribute to the development of long-term neurological symptoms and structural alterations in the gray matter. However, the existence of a consistent pattern of cerebral atrophy remains uncertain.

OBJECTIVE

Our study aimed to identify patterns of brain involvement in recovered COVID-19 patients and explore potential relationships with clinical variables during hospitalization.

METHODOLOGY

In this study, we included 39 recovered patients and 39 controls from a pre-pandemic database to ensure their non-exposure to the virus. We obtained clinical data of the patients during hospitalization, and 3 months later; in addition we obtained T1-weighted magnetic resonance images and performed standard screening cognitive tests.

RESULTS

We identified two groups of recovered patients based on a cluster analysis of the significant cortical thickness differences between patients and controls. Group 1 displayed significant cortical thickness differences in specific cerebral regions, while Group 2 exhibited significant differences in the cerebellum, though neither group showed cognitive deterioration at the group level. Notably, Group 1 showed a tendency of higher D-dimer values during hospitalization compared to Group 2, prior to p-value correction.

CONCLUSION

This data-driven division into two groups based on the brain structural differences, and the possible link to D-dimer values may provide insights into the underlying mechanisms of SARS-COV-2 neurological disruption and its impact on the brain during and after recovery from the disease.

Inflammatory Polymorphisms (IL-6 rs1800796, IL-10 rs1800896, TNF-α rs1800629, and IFITM3 rs12252) Are Not Associated with Post-COVID Symptoms in Previously Hospitalized COVID-19 Survivors

The aim of this study was to identify the association between four selected inflammatory polymorphisms with the development of long-term post-COVID symptoms in subjects who had been hospitalized due to SARS-CoV-2 infection during the first wave of the pandemic. These polymorphisms were selected as they are associated with severe COVID-19 disease and cytokine storm, so they could be important to prognoses post-COVID. A total of 408 (48.5% female, age: 58.5 ± 14.0 years) previously hospitalized COVID-19 survivors participated. The three potential genotypes of the following four single-nucleotide polymorphisms, IL-6 rs1800796, IL-10 rs1800896, TNF-α rs1800629, and IFITM3 rs12252, were obtained from non-stimulated saliva samples of the participants. The participants were asked to self-report the presence of any post-COVID symptoms (defined as symptoms that had started no later than one month after SARS-CoV-2 acute infection) and whether the symptoms persisted at the time of the study. At the time of the study (mean: 15.6, SD: 5.6 months after discharge), 89.4% of patients reported at least one post-COVID symptom (mean number of symptoms: 3.0; SD: 1.7). Fatigue (69.3%), pain (40.9%), and memory loss (27.2%) were the most prevalent post-COVID symptoms in the total sample. Overall, no differences in the post-COVID symptoms depending on the IL-6 rs1800796, IL-10 rs1800896, TNF-α rs1800629, and IFITM3 rs12252 genotypes were seen. The four SNPs assessed, albeit having been previously associated with inflammation and COVID-19 severity, did not cause a predisposition to the development of post-COVID symptoms in the previously hospitalized COVID-19 survivors.

Long COVID: neurological manifestations - an updated narrative review

Infection with the SARS-CoV-2 virus can lead to neurological symptoms in the acute phase and in the Long COVID phase. These symptoms usually involve cognition, sleep, smell disorders, psychiatric manifestations, headache and others. This condition is more commonly described in young adults and women. This symptomatology can follow severe or mild cases of the disease. The importance of this issue resides in the high prevalence of neurological symptoms in the Long COVID phase, which entails significant morbidity in this population. In addition, such a condition is associated with high health care costs, with some estimates hovering around 3.7 trillion US dollars. In this review, we will sequentially describe the current knowledge about the most prevalent neurological symptoms in Long COVID, as well as their pathophysiology and possible biomarkers.

Social Inequalities in Long-Term Health Effects After COVID-19-A Scoping Review

Objectives: We aimed to map and synthesize evidence about social inequalities in long-term health effects after COVID-19 (LTHE), often referred to as "long COVID" or "post-COVID-19 conditions." Methods: We conducted a scoping review of peer-reviewed articles by searching the databases Embase and Scopus. According to predefined inclusion criteria, titles/abstracts and full texts were screened for eligibility. Additionally, reference lists of all included studies were hand-searched for eligible studies. This study followed the PRISMA guidelines for scoping reviews. Results: Nineteen articles were included. LTHE were analysed according to ethnicity, education, income, employment and deprivation indices. The studies varied significantly in their definitions of LTHE. Eighty-two analyses showed no statistically significant associations. At least 12 studies had a high risk of type II errors. Only studies associating deprivation indices and long COVID tended to show a higher prevalence of LTHE in deprived areas. Conclusion: Although some studies indicated social inequalities in LTHE, evidence was generally weak and inconclusive. Further studies with larger sample sizes specifically designed to detect social inequalities regarding LTHE are needed to inform future healthcare planning and public health policies.

The incidence, characteristics, impact and risk factors of post-COVID chronic pain in Thailand: A single-center cross-sectional study

The COVID-19 pandemic has affected millions of individuals worldwide. Pain has emerged as a significant post-COVID-19 symptom. This study investigated the incidence, characteristics, and risk factors of post-COVID chronic pain (PCCP) in Thailand. A cross-sectional study was conducted in participants who had been infected, including those hospitalized and monitored at home by SARS-CoV-2 from August to September 2021. Data were collected for screening from medical records, and phone interviews were done between 3 to 6 months post-infection. Participants were classified into 1) no-pain, 2) PCCP, 3) chronic pain that has been aggravated by COVID-19, or 4) chronic pain that has not been aggravated by COVID-19. Pain interference and quality of life were evaluated with the Brief Pain Inventory and EuroQol Five Dimensions Five Levels Questionnaire. From 1,019 participants, 90% of the participants had mild infection, assessed by WHO progression scale. The overall incidence of PCCP was 3.2% (95% CI 2.3-4.5), with 2.8% (95% CI 2.0-4.1) in mild infection, 5.2% (95% CI 1.2-14.1) in moderate infection and 8.5% (95% CI 3.4-19.9) in severe infection. Most participants (83.3%) reported pain in the back and lower extremities and were classified as musculoskeletal pain and headache (8.3%). Risk factors associated with PCCP, included female sex (relative risk [RR] 2.2, 95% CI 1.0-4.9) and greater COVID-19 severity (RR 3.5, 95% CI 1.1-11.7). Participants with COVID-19-related exacerbated chronic pain displayed higher pain interferences and lower utility scores than other groups. In conclusion, this study highlights the incidence, features, and risk factors of post-COVID chronic pain (PCCP) in Thailand. It emphasizes the need to monitor and address PCCP, especially in severe cases, among females, and individuals with a history of chronic pain to improve their quality of life in the context of the ongoing COVID-19 pandemic.

Systematic review and evidence gap mapping of biomarkers associated with neurological manifestations in patients with COVID-19

OBJECTIVE

This study aimed to synthesize the existing evidence on biomarkers related to coronavirus disease 2019 (COVID-19) patients who presented neurological events.

METHODS

A systematic review of observational studies (any design) following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and the Cochrane Collaboration recommendations was performed (PROSPERO: CRD42021266995). Searches were conducted in PubMed and Scopus (updated April 2023). The methodological quality of nonrandomized studies was assessed using the Newcastle‒Ottawa Scale (NOS). An evidence gap map was built considering the reported biomarkers and NOS results.

RESULTS

Nine specific markers of glial activation and neuronal injury were mapped from 35 studies published between 2020 and 2023. A total of 2,237 adult patients were evaluated in the included studies, especially during the acute phase of COVID-19. Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) biomarkers were the most frequently assessed (n = 27 studies, 77%, and n = 14 studies, 40%, respectively). Although these biomarkers were found to be correlated with disease severity and worse outcomes in the acute phase in several studies (p < 0.05), they were not necessarily associated with neurological events. Overall, 12 studies (34%) were judged as having low methodological quality, 9 (26%) had moderate quality, and 9 (26%) had high quality.

CONCLUSIONS

Different neurological biomarkers in neurosymptomatic COVID-19 patients were identified in observational studies. Although the evidence is still scarce and conflicting for some biomarkers, well-designed longitudinal studies should further explore the pathophysiological role of NfL, GFAP, and tau protein and their potential use for COVID-19 diagnosis and management.

Bilateral Avascular Necrosis of the Femoral Heads After COVID-19 Infection without Steroid Treatment

BACKGROUND

Avascular necrosis (AVN) is a potentially serious multifactorial disease. In COVID-19 patients, AVN of many bones has been reported. Usually, the condition is linked to steroid therapy. In this case report, we describe our experience with bilateral AVN of femoral heads in an elderly patient months after being cured of COVID-19 infection without the use of steroids.

CASE PRESENTATION

A 68-year-old male was referred to the outpatient clinic of the rheumatology and rehabilitation department for progressive bilateral hip pain starting on the left side 5 months ago. An extensive review of the patient's medical history identified documented COVID-19 infection that required hospitalization 9 months before presentation. Multiplanar MRI with fat suppression of both hips showed ill-defined areas of abnormal signal intensity affecting the left femoral head, neck and intertrochanteric regions with associated subchondral fissuring and mild joint effusion. A similar smaller area was also seen affecting the postero-superior aspect of the right femoral head.

CONCLUSION

AVN in COVID-19 patients can be encountered even in the absence of steroid therapy.

The Clinical Aspects of COVID and Alzheimer's Disease: A Round-Up of Where Things Stand and Are Headed

 The link between long COVID-19 and brain/cognitive impairments is concerning and may foster a worrisome worldwide emergence of novel cases of neurodegenerative diseases with aging. This review aims to update the knowledge, crosstalk, and possible intersections between the Post-COVID Syndrome (PCS) and Alzheimer's disease (AD). References included in this review were obtained from PubMed searches conducted between October 2023 and November 2023. PCS is a very heterogenous and poorly understood disease with recent evidence of a possible association with chronic diseases such as AD. However, more scientific data is required to establish the link between PCS and AD.

Interleukin 6 Antagonists in Severe COVID-19 Disease: Cardiovascular and Respiratory Outcomes

BACKGROUND

Inhibitors of interleukin 6 [IL-6] have been utilized to treat severe COVID-19 disease. Their immunosuppressive or immunomodulating impact may be beneficial in COVID-19.

OBJECTIVES

To discuss the role of IL-6 inhibitors and assess various trials conducted to evaluate the efficacy of IL-6 inhibitors in COVID-19 disease.

SUMMARY

Two of the most common causes of mortality in COVID-19-infected critically ill individuals are acute respiratory distress syndrome (ARDS) and multiorgan failure. Increased levels of inflammatory cytokines suggest that a cytokine storm, also known as cytokine release syndrome (CRS), is involved in the etiology of COVID-19. Most tissue damage, sepsis, and pulmonary and cardiovascular problems are caused mainly by the host defense system. Therefore, regulating this inflammatory cascade using immunomodulators is a prudent strategy. Although corticosteroids, as immunomodulators, are routinely used in COVID-19 management, interleukin (IL) inhibitors, especially IL-6 inhibitors, are also tested in many trials. Many studies have demonstrated that IL-6 inhibitors improve disease outcomes and decrease mortality, whereas others have shown that they are ineffective. In this paper, we briefly examined the role of IL-6 in COVID-19 pathogenesis and trials that support or refute the use of IL-6 inhibitors in treating COVID-19 disease.

RESULTS

Though mixed results are coming from trials regarding the adjuvant use of IL-6 inhibitors and standard anti-viral therapy with dexamethasone, a consensus favors using IL-6 inhibitors in severely ill COVID-19 patients regardless of the outcome.

Heightened Prevalence of Common Hospital-Treated Infections Preceding Dementia Diagnosis with Accelerated Dementia Onset after Influenza

BACKGROUND

Since the beginning of Alzheimer's disease research, the hypothesis that infections are to some extent associated with neurodegenerative processes has been tested repeatedly. Epidemiological studies on the associations between infections and dementia have reported conflicting results.

OBJECTIVES

This study analyses common hospital-treated infections (herpes, influenza, intestinal infections, pneumonia, sepsis, urinary tract infections) and their association with subsequent dementia and time until dementia onset.

DESIGN, SETTING, AND PARTICIPANTS

For this nationwide population-based case-control study, the dataset of the Austrian National Health Insurance Association was used, including dementia patients (dementia cohort) and age- and gender-matched non-demented individuals (control cohort). Only subjects with data availability of at least 10 years prior to the index date (date of dementia diagnosis or date of censoring) were included.

MEASUREMENTS

The incidence of six common infections in older adults (herpes, influenza, intestinal infections, pneumonia, sepsis, and urinary tract infections) was analyzed over a period of 10 years before the censoring date.

RESULTS

The study population consists of 58208 subjects (29104 per study cohort), mean age: 81 years, 54% females. Patients of the dementia cohort had suffered from infections significantly more often than patients of the control cohort (6002, 20.6% vs. 4826, 16.6%; p < 0.001). Influenza, urinary tract infections, intestinal infections, and sepsis showed independent positive associations with subsequent dementia diagnosis, irrespective of other comorbidities (odds ratios: 1.26 (95% CI: 1.06-1.49), 1.23 (95% CI: 1.16-1.30), 1.16 (95% CI: 1.07-1.27), 1.17 (95% CI: 1.01-1.37), respectively). Time from infection to dementia diagnosis was shorter after influenza compared to all other infections (median: 3.4 years (95% CI: 3.1-3.7) vs. 6.6 years (95% CI: 6.4-6.8); p < 0.001).

CONCLUSION

This is the first study to assess the association between infections and dementia over such a long minimum reporting period. These results, supported by consistent data from other epidemiological studies, emphasize the critical importance of infection prevention measures, especially for older adults. Further research is crucial to better understand the nature of the relationship between infections and dementia.

Long COVID: Molecular Mechanisms and Detection Techniques

Long COVID, also known as post-acute sequelae of SARS-CoV-2 infection (PASC), has emerged as a significant health concern following the COVID-19 pandemic. Molecular mechanisms underlying the occurrence and progression of long COVID include viral persistence, immune dysregulation, endothelial dysfunction, and neurological involvement, and highlight the need for further research to develop targeted therapies for this condition. While a clearer picture of the clinical symptomatology is shaping, many molecular mechanisms are yet to be unraveled, given their complexity and high level of interaction with other metabolic pathways. This review summarizes some of the most important symptoms and associated molecular mechanisms that occur in long COVID, as well as the most relevant molecular techniques that can be used in understanding the viral pathogen, its affinity towards the host, and the possible outcomes of host-pathogen interaction.

Assessment of Some Risk Factors and Biological Predictors in the Post COVID-19 Syndrome in Asthmatic Patients

Long COVID-19 or post-COVID infection (PCI) refers to the prolongation of symptoms in people who have been infected with the SARS-CoV-2 virus. Some meta-analysis studies have shown that patients with comorbidities, such as diabetes, obesity or hypertension, have severe complications after infection with the SARS-CoV-2 virus. The presence of chronic respiratory diseases such as bronchial asthma, COPD, pulmonary hypertension or cystic fibrosis increases the risk of developing severe forms of the COVID-19 disease. The risk of developing the severe form of COVID-19 was observed in patients with bronchial asthma being treated with corticosteroids, but also in those hospitalized with severe asthma. The biological variables determined in patients with PCI infection showed changes, especially in the hematological parameters, but also in some inflammatory markers. The aim of this study was to investigate some biological predictors in post-COVID-19 infection in patients with asthma and various comorbidities. In the case of patients diagnosed with moderate and severe forms of COVID-19, the variation in biological tests has shown high concentrations for serum glucose, lactate dehydrogenase and C-reactive protein. Additionally, the calculation of the relative risk (RR) based on the associated comorbidities in patients with PCI points to higher values for patients with asthma, hypertension, diabetes and obesity (RR moderate/severe form = 0.98/1.52), compared to patients with PCI and asthma (RR moderate/severe form = 0.36/0.63). Based on the statistical results, it can be concluded that the alanine aminotransferase (ALT) activity (p = 0.006) and the age of patients (p = 0.001) are the variables that contribute the most to the separation of the four classes of comorbidities considered.

Long COVID or Post-COVID-19 Condition: Past, Present and Future Research Directions

The presence of symptoms after an acute SARS-CoV-2 infection (long-COVID) has become a worldwide healthcare emergency but remains underestimated and undertreated due to a lack of recognition of the condition and knowledge of the underlying mechanisms. In fact, the prevalence of post-COVID symptoms ranges from 50% during the first months after the infection up to 20% two-years after. This perspective review aimed to map the existing literature on post-COVID symptoms and to identify gaps in the literature to guide the global effort toward an improved understanding of long-COVID and suggest future research directions. There is a plethora of symptomatology that can be due to COVID-19; however, today, there is no clear classification and definition of this condition, termed long-COVID or post-COVID-19 condition. The heterogeneity in the symptomatology has led to the presence of groups/clusters of patients, which could exhibit different risk factors and different mechanisms. Viral persistence, long-lasting inflammation, immune dysregulation, autoimmune reactions, reactivation of latent infections, endothelial dysfunction and alteration in gut microbiota have been proposed as potential mechanisms explaining the complexity of long-COVID. In such an equation, viral biology (e.g., re-infections, SARS-CoV-2 variants), host biology (e.g., genetics, epigenetics) and external factors (e.g., vaccination) should be also considered. These various factors will be discussed in the current perspective review and future directions suggested.

Molecular Mechanisms of Pathogenesis, Prevention, and Therapy of COVID-19: Summarizing the Results of 2022

The aim of this Special Issue is to analyze the key patterns of the 2019 coronavirus disease pandemic (COVID-19), the biology of SARS-CoV-2 (severe-acute-respiratory-syndrome-related coronavirus 2, formerly 2019-nCoV), and the characteristics of the human body's response to the invasion of this virus [...].

Lactate dehydrogenase contribution to symptom persistence in long COVID: A pooled analysis

There's critical need for risk predictors in long COVID. This meta-analysis evaluates the evidence for an association between plasma lactate dehydrogenase (LDH) and long COVID and explores the contribution of LDH to symptoms persistent across the distinct post-acute sequelae of COVID-19 (PASC) domains. PubMed, EMBASE, Web of Science, and Google Scholar were searched for articles published up to 20 March 2023 for studies that reported data on LDH levels in COVID-19 survivors with and without PASC. Random-effect meta-analysis was employed to estimate the standardized mean difference (SMD) with corresponding 95% confidence interval of each outcome. There were a total of 8289 study participants (3338 PASC vs. 4951 controls) from 46 studies. Our meta-analysis compared to the controls showed a significant association between LDH elevation and Resp-PASC [SMD = 1.07, 95%CI = 0.72, 1.41, p = 0.01] but not Cardio-PASC [SMD = 1.79, 95%CI = -0.02, 3.61, p = 0.05], Neuro-PASC [SMD = 0.19, 95%CI = -0.24, 0.61, p = 0.40], and Gastrointestinal-PASC [SMD = 0.45, 95%CI = -1.08, 1.98, p = 0.56]. This meta-analysis suggests elevated LDH can be used for predicting Resp-PASC, but not Cardio-PASC, Neuro-PASC or gastrointestinal-PASC. Thus, elevated plasma LDH following COVID infection may be considered as a disease biomarker.

Single-cell RNA sequencing analysis and Alzheimer's disease: a bibliometric analysis

Alzheimer's disease (AD) is a devastative disease, the 1st most frequent neurodegenerative disease worldwide. Its prevalence is increasing and early detection methods as well as potential genomic based therapeutics are urgently needed.

OBJECTIVES

To better characterize recent seq studies of AD and site recent relevant literature. Using single-cell RNA sequencing, the characteristics of neuronal cell populations in Alzheimer's disease (AD) have not been completely elucidated.

METHODS

We conducted a dynamic and longitudinal bibliometric analysis to investigate existing studies on Single-cell RNA sequencing analysis and Alzheimer's Disease and identify data gaps and possible new research avenues.

RESULTS

All AD papers concentrating on Single-cell RNA sequencing analysis were found using the search terms "Alzheimer's Disease", and "Single-cell RNA sequencing analysis" in the PubMed/MEDLINE database. Only English publications published between 2015 and 2023 were chosen using filters.

CONCLUSIONS

Original English-language research publications disclosing Single-cell RNA sequencing analysis and Alzheimer's Disease were examined for inclusion. Two sets of independent reviewers discovered and extracted pertinent data. The bibliometric study was carried out using the R software packages Bibliometrix and Biblioshiny. The narrowed search yielded 158 publications, all published between 2015 and 2023. Yet, after applying filters and considering the inclusion requirements, the search results comprise just 51 original articles out of 158 articles. There were 107 articles eliminated. The importance of the discovery of Single-cell RNA sequencing analysis and Alzheimer's Disease a decade ago only grows with time. Our results have important implications for future studies of AD and may help researchers across the world better understand the global context of the Single-cell RNA sequencing analysis and Alzheimer's Disease link. This study puts emphasis on the critical need for more diverse participant demographics in Alzheimer's disease investigations.

Circulating calprotectin levels four months after severe and non-severe COVID-19

BACKGROUND

Calprotectin is an inflammatory marker mainly released by activated neutrophils that is increased in acute severe COVID-19. After initial recovery, some patients have persistent respiratory impairment with reduced diffusion capacity of the lungs for carbon monoxide (DLCO) months after infection. Underlying causes of this persistent impairment are unclear. We aimed to investigate the correlation between circulating calprotectin, persistent lung functional impairment and intensive care unit (ICU) stay after COVID-19 in two university hospital centres in Switzerland.

METHODS

Calprotectin levels were measured in serum from 124 patients (50% male) from the Bern cohort (post-ICU and non-ICU patients) and 68 (76% male) from the Lausanne cohort (only post-ICU patients) four months after COVID-19. Calprotectin was correlated with clinical parameters. Multivariate linear regression (MLR) was performed to evaluate the independent association of calprotectin in different models.

RESULTS

Overall, we found that post-ICU patients, compared to non-ICU, were significantly older (age 59.4 ± 13.6 (Bern), 60.5 ± 12.0 (Lausanne) vs. 48.8 ± 13.4 years) and more obese (BMI 28.6 ± 4.5 and 29.1 ± 5.3 vs. 25.2 ± 6.0 kg/m2, respectively). 48% of patients from Lausanne and 44% of the post-ICU Bern cohort had arterial hypertension as a pre-existing comorbidity vs. only 10% in non-ICU patients. Four months after COVID-19 infection, DLCO was lower in post-ICU patients (75.96 ± 19.05% predicted Bern, 71.11 ± 18.50% Lausanne) compared to non-ICU (97.79 ± 21.70% predicted, p < 0.01). The post-ICU cohort in Lausanne had similar calprotectin levels when compared to the cohort in Bern (Bern 2.74 ± 1.15 µg/ml, Lausanne 2.49 ± 1.13 µg/ml vs. non-ICU 1.86 ± 1.02 µg/ml; p-value < 0.01). Calprotectin correlated negatively with DLCO (r= -0.290, p < 0.001) and the forced vital capacity (FVC) (r= -0.311, p < 0.001).

CONCLUSIONS

Serum calprotectin is elevated in post-ICU patients in two independent cohorts and higher compared to non-ICU patients four months after COVID-19. In addition, there is a negative correlation between calprotectin levels and DLCO or FVC. The relationship between inflammation and lung functional impairment needs further investigations.

TRIAL REGISTRATION

NCT04581135.

Intrinsic factors behind long-COVID: II. SARS-CoV-2, extracellular vesicles, and neurological disorders

With the decline in the number of new Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections, the World Health Organization announced the end of the SARS-CoV-2 pandemic. However, the repercussions of this viral pandemic may remain with us for a longer period of time, as it has remodeled the lives of humankind in many ways, including social and economic. Of course, its most important repercussions remain on the human health level. Long-coronavirus disease (COVID) or post-COVID is a state for which we do not have a concrete definition, a specific international classification of diseases Code, clear diagnostic tools, or well-known effective cures as of yet. In this second article from the Intrinsic Factors behind long-COVID Series, we try to link long-COVID symptoms with their causes, starting from the nervous system. Extracellular vesicles (ECVs) play very complex and ramified roles in the bodies of both healthy and not-healthy individuals. ECVs may facilitate the entry of many bioactive molecules and pathogens into the tissues and cells of the nervous system across the blood-brain barrier. Based on the size, quantity, and quality of their cargo, ECVs are directly proportional to the pathological condition and its severity through intertwined mechanisms that evoke inflammatory immune responses typically accompanied by pathological symptoms over variable time periods according to the type of these symptoms.

Characterizing long-COVID brain fog: a retrospective cohort study

BACKGROUND

Long COVID or post-COVID condition (PCC) is a common complication following acute COVID-19 infection. PCC is a multi-systems disease with neurocognitive impairment frequently reported regardless of age. Little is known about the risk factors, associated biomarkers and clinical trajectory of patients with this symptom.

OBJECTIVE

To determine differences in clinical risk factors, associated biochemical markers and longitudinal clinical trajectories between patients with PCC with subjective neurocognitive symptoms (NC+) or without (NC-).

METHODS

A retrospective longitudinal cohort study was performed using a well-characterized provincial database of patients with clinically confirmed PCC separated into NC+ and NC- cohorts. Demographical, clinical and biochemical differences at initial consultation between the two patient cohorts were analyzed in cross-section. Multivariate regression analyses were conducted to identify independent risk factors for neurocognitive impairment. Determination of the recovery trajectory was performed using serial assessments of the patient-reported health-related quality of life (HR-QoL) metric Eq-5D-5L-vas score.

FINDINGS

Women, milder acute infection and pre-existing mental health diagnoses were independently associated with subjective neurocognitive impairment at 8 months post-infection. NC + patients demonstrated lower levels of IgG, IgG1 and IgG3 compared to NC- patients. The NC + cohort had poorer HR-QoL at initial consultation 8 months post-infection with gradual improvement over 20 months post-infection.

CONCLUSIONS

Neurocognitive impairment represents a severe phenotype of PCC, associated with unique risk factors, aberrancy in immune response and a delayed recovery trajectory. Those with risk factors for neurocognitive impairment can be identified early in the disease trajectory for more intense medical follow-up.

Usefulness of the Veterans Health Administration COVID-19 (VACO) Index for Predicting Short-Term Mortality among Patients of the COLOS Study

Advanced age is known to be a predictor with COVID-19 severity. Understanding of other disease progression factors may shorten the time from patient admission to applied treatment. The Veterans Health Administration COVID-19 (VACO index) was assumed to additionally anticipate clinical results of patients hospitalized with a proven infection caused by the SARS-CoV-2 virus.

METHODS

The medical records of 2183 hospitalized patients were retrospectively analyzed. Patients were divided into four risk-of-death categories: low risk, medium risk, high-risk, and extreme risk depending on their VACO index calculation.

RESULTS

Significant differences in the mortality at the hospital after three months of discharge and six months after discharge were noticed. For the patients in the extreme-risk group, mortality reached 37.42%, 62.81%, and 78.44% for in-hospital, three months of discharge, and six months of discharge, respectively. The mortality marked as high risk reached 20.38%, 37.19%, and 58.77%. Moreover, the secondary outcomes analysis acknowledged that patients classified as extreme risk were more likely to suffer from cardiogenic shock, myocardial infarction, myocardial injury, stroke, pneumonia, acute kidney injury, and acute liver dysfunction. Patients at moderate risk were more often admitted to ICU when compared to other patients.

CONCLUSIONS

The usage of the VACO index, combined with an appropriate well-defined medical interview and past medical history, tends to be a helpful instrument in order to predict short-term mortality and disease progression based on previous medical records.