Challenges and opportunities in long COVID research.

Long COVID (LC) is a condition in which patients do not fully recover from the initial SARS-CoV-2 infection but rather have persistent or new symptoms for months to years following the infection. Ongoing research efforts are investigating the pathophysiologic mechanisms of LC and exploring preventative and therapeutic treatment approaches for patients. As a burgeoning area of investigation, LC research can be structured to be more inclusive, innovative, and effective. In this perspective, we highlight opportunities for patient engagement and diverse research expertise, as well as the challenges of developing definitions and reproducible studies. Our intention is to provide a foundation for collaboration and progress in understanding the biomarkers and mechanisms driving LC.

Post-COVID-19 Condition.

An estimated 10-15% of those infected with SARS-CoV-2 may have post-COVID-19 condition. Common lingering signs and symptoms include shortness of breath, fatigue, high heart rate, and memory and cognitive dysfunction even several months after infection, often impacting survivors' quality of life. The prevalence and duration of individual symptoms remain difficult to ascertain due to the lack of standardized research methods across various studies and limited patient follow-up in clinical studies. Nonetheless, data indicate post-COVID-19 condition may occur independent of acuity of initial infection, hospitalization status, age, or pre-existing comorbidities. Risk factors may include female sex and underlying respiratory or psychiatric disease. Supportive therapies to mitigate symptoms remain the mainstay of treatment. Reassuringly, most patients experience a reduction in symptoms by 1 year. The use of a universal case definition and shared research methods will allow for further clarity regarding the pervasiveness of this entity and its long-term health consequences.

The impact of long COVID on health-related quality of life in patients 6 months after discharge with severe COVID-19.

This study investigates the relationship between long COVID and health-related quality of life (HRQOL) in patients discharged for 6 months. It included 192 patients with a history of severe COVID-19 and 192 patients with a history of non-severe COVID-19 patients that were selected through quota sampling methods from the Medical Care Monitoring Center (MCMC) of hospitals in Shiraz, Iran, in 2020. Phone-based interviews were conducted to collect data using the short form of the 12-item health-related quality of life (SF-12) questionnaire. Descriptive statistics, including mean (standard deviation) and frequency (percentage), were utilized. Statistical tests, such as the chi-squared test, independent samples t-test, Fisher's exact test, and multiple linear regression models were performed. Statistical analysis was performed using SPSS software version 24, with a significance level of 0.05. Among 384 patients, 79.95% were married, with a mean age of 53.95 years. The majority of patients in both groups were male (57.81% in the severe group and 51.04% in the non-severe group). Patients with severe COVID-19 had significantly lower quality of life scores compared to those with non-severe COVID-19 (p < 0.001, 34.45 [SD = 6.59] versus 39.64 [SD = 5.07]). Furthermore, multiple linear regression analysis indicated that severe COVID-19 inducts a significant negative effect on HRQOL in patients after adjustment of confounders (p < 0.001, B = - 4.84). Patients with severe COVID-19 had lower HRQOL compared to those with a non-severe level. It is necessary to consider implementing policies aimed at providing social, psychological, or medical support to improve the HRQOL of patients with a history of severe COVID-19.

Efficacy of dual-task augmented reality rehabilitation in non-hospitalized adults with self-reported long COVID fatigue and cognitive impairment: a pilot study.

BACKGROUND: Cognitive impairment and chronic fatigue represent common characteristics of the long COVID syndrome. Different non-pharmacological treatments have been proposed, and physiotherapy has been proposed to improve the symptoms. This study aimed to evaluate the effects of a dual-task augmented reality rehabilitation protocol in people with long COVID fatigue and cognitive impairment. METHODS AND MATERIALS: Ten non-hospitalized adults with reported fatigue and "brain fog" symptoms after COVID (7/10 females, 50 years, range 41-58) who participated in 20 sessions of a 1-h "dual-task" training, were compared to 10 long COVID individuals with similar demographics and symptoms (9/10 females, 56 years, range 43-65), who did not participate to any rehabilitation protocol. Cognitive performance was assessed with the Trail Making Test (TMT-A and -B) and Frontal Assessment Battery (FAB), and cardiovascular and muscular fatigue were assessed with the fatigue severity scale (FSS), six-minute walking test and handgrip endurance. Finally, transcranial magnetic stimulation (TMS) investigated cortical excitability. RESULTS: The mixed-factors analysis of variance found a significant interaction effect only in cognitive performance evaluation, suggesting TMT-B execution time decreased (- 15.9 s, 95% CI 7.6-24.1, P = 0.001) and FAB score improved (1.88, 95% CI 2.93-0.82, P = 0.002) only in the physiotherapy group. For the remaining outcomes, no interaction effect was found, and most parameters similarly improved in the two groups. CONCLUSION: The preliminary results from this study suggest that dual-task rehabilitation could be a feasible protocol to support cognitive symptoms recovery after COVID-19 and could be helpful in those individuals suffering from persisting and invalidating symptoms.

The Epidemiology of Long Coronavirus Disease in US Adults.

BACKGROUND: We estimated the prevalence of long COVID and impact on daily living among a representative sample of adults in the United States. METHODS: We conducted a population-representative survey, 30 June-2 July 2022, of a random sample of 3042 US adults aged 18 years or older and weighted to the 2020 US population. Using questions developed by the UK's Office of National Statistics, we estimated the prevalence of long COVID, by sociodemographics, adjusting for gender and age. RESULTS: An estimated 7.3% (95% confidence interval: 6.1-8.5%) of all respondents reported long COVID, corresponding to approximately 18 828 696 adults. One-quarter (25.3% [18.2-32.4%]) of respondents with long COVID reported their day-to-day activities were impacted "a lot" and 28.9% had severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection more than 12 months ago. The prevalence of long COVID was higher among respondents who were female (adjusted prevalence ratio [aPR]: 1.84 [1.40-2.42]), had comorbidities (aPR: 1.55 [1.19-2.00]), or were not (vs were) boosted (aPR: 1.67 [1.19-2.34]) or not vaccinated (vs boosted) (aPR: 1.41 [1.05-1.91]). CONCLUSIONS: We observed a high burden of long COVID, substantial variability in prevalence of SARS-CoV-2, and risk factors unique from SARS-CoV-2 risk, suggesting areas for future research. Population-based surveys are an important surveillance tool and supplement to ongoing efforts to monitor long COVID.

Cognitive dysfunction in post-COVID-19 condition: Mechanisms, management, and rehabilitation.

The long-term effects of COVID-19 on cognitive function have become an area of increasing concern. This paper provides an overview of characteristics, risk factors, possible mechanisms, and management strategies for cognitive dysfunction in post-COVID-19 condition (PCC). Prolonged cognitive dysfunction is one of the most common impairments in PCC, affecting between 17% and 28% of the individuals more than 12 weeks after the infection and persisting in some cases for several years. Cognitive dysfunctions can be manifested as a wide range of symptoms including memory impairment, attention deficit, executive dysfunction, and reduced processing speed. Risk factors for developing PCC, with or without cognitive impairments, include advanced age, preexisting medical conditions, and the severity of acute illness. The underlying mechanisms remain unclear, but proposed contributors include neuroinflammation, hypoxia, vascular damage, and latent virus reactivation not excluding the possibility of direct viral invasion of the central nervous system, illustrating complex viral pathology. As the individual variation of the cognitive impairments is large, a neuropsychological examination and a person-centered multidimensional approach are required. According to the World Health Organization, limited evidence on COVID-19-related cognitive impairments necessitates implementing rehabilitation interventions from established practices of similar conditions. Psychoeducation and compensatory skills training are recommended. Assistive products and environmental modifications adapted to individual needs might be helpful. In specific attention- and working memory dysfunctions, cognitive training-carefully monitored for intensity-might be effective for people who do not suffer from post-exertional malaise. Further research is crucial for evidence-based interventions specific to COVID-19-related cognitive impairments.

Leveraging Serologic Testing to Identify Children at Risk For Post-Acute Sequelae of SARS-CoV-2 Infection: An Electronic Health Record-Based Cohort Study from the RECOVER Program.

Using an electronic health record-based algorithm, we identified children with Coronavirus disease 2019 (COVID-19) based exclusively on serologic testing between March 2020 and April 2022. Compared with the 131 537 polymerase chain reaction-positive children, the 2714 serology-positive children were more likely to be inpatients (24% vs 2%), to have a chronic condition (37% vs 24%), and to have a diagnosis of multisystem inflammatory syndrome in children (23% vs <1%). Identification of children who could have been asymptomatic or paucisymptomatic and not tested is critical to define the burden of post-acute sequelae of severe acute respiratory syndrome coronavirus 2 infection in children.

Treatable traits for long COVID.

Long COVID, or post-acute COVID-19 sequelae, is experienced by an estimated one in eight adults following acute COVID-19. Long COVID is a new and complex chronic health condition that typically includes multiple symptoms that cross organ systems and fluctuate over time; a one-size-fits-all approach is, therefore, not likely to be appropriate nor relevant for long COVID treatment. 'Treatable Traits' is a personalized medicine approach, purpose-built to address the complexity and heterogeneity of complex chronic conditions. This comprehensive review aimed to understand how a treatable traits approach could be applied to long COVID, by first identifying the most prevalent long COVID treatable traits and then the available evidence for strategies to target these traits. An umbrella review of 22 systematic reviews identified 34 symptoms and complications common with long COVID, grouped into eight long COVID treatable trait clusters: neurological, chest, psychological, pain, fatigue, sleep impairment, functional impairment and other. A systematic review of randomized control trials identified 18 studies that explored different intervention approaches for long COVID prevention (k = 4) or management (k = 14). While a single study reported metformin as effective for long COVID prevention, the findings need to be replicated and consensus is required around how to define long COVID as a clinical trial endpoint. For long COVID management, current evidence supports exercise training or respiratory muscle training for long COVID treatable traits in the chest and functional limitation clusters. While there are studies exploring interventions targeting other long COVID treatable traits, further high-quality RCTs are needed, particularly targeting treatable traits in the clusters of fatigue, psychological, pain and sleep impairment.

SARS-CoV-2 Reinfections and Long COVID in the Post-Omicron Phase of the Pandemic.

We are reviewing the current state of knowledge on the virological and immunological correlates of long COVID, focusing on recent evidence for the possible association between the increasing number of SARS-CoV-2 reinfections and the parallel pandemic of long COVID. The severity of reinfections largely depends on the severity of the initial episode; in turn, this is determined both by a combination of genetic factors, particularly related to the innate immune response, and by the pathogenicity of the specific variant, especially its ability to infect and induce syncytia formation at the lower respiratory tract. The cumulative risk of long COVID as well as of various cardiac, pulmonary, or neurological complications increases proportionally to the number of SARS-CoV-2 infections, primarily in the elderly. Therefore, the number of long COVID cases is expected to remain high in the future. Reinfections apparently increase the likelihood of long COVID, but less so if they are mild or asymptomatic as in children and adolescents. Strategies to prevent SARS-CoV-2 reinfections are urgently needed, primarily among older adults who have a higher burden of comorbidities. Follow-up studies using an established case definition and precise diagnostic criteria of long COVID in people with or without reinfection may further elucidate the contribution of SARS-CoV-2 reinfections to the long COVID burden. Although accumulating evidence supports vaccination, both before and after the SARS-CoV-2 infection, as a preventive strategy to reduce the risk of long COVID, more robust comparative observational studies, including randomized trials, are needed to provide conclusive evidence of the effectiveness of vaccination in preventing or mitigating long COVID in all age groups. Thankfully, answers not only on the prevention, but also on treatment options and rates of recovery from long COVID are gradually starting to emerge.

Small fiber neuropathy associated with SARS-CoV-2 infection.

INTRODUCTION/AIMS: The development and persistence of neurological symptoms following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is referred to as "long-haul" syndrome. We aimed to determine whether small fiber neuropathy (SFN) was associated with SARS-CoV-2 infection. METHODS: We retrospectively studied the clinical features and outcomes of patients who were referred to us between May 2020 and May 2021 for painful paresthesia and numbness that developed during or after SARS-CoV-2 infection and who had nerve conduction studies showing no evidence of a large fiber polyneuropathy. RESULTS: We identified 13 patients, Eight women and five men with age ranging from 38-67 y. Follow-up duration ranged from 8 to 12 mo. All patients developed new-onset paresthesias within 2 mo following SARS-CoV-2 infection, with an acute onset in seven and co-existing autonomic symptoms in seven. Three patients had pre-existing but controlled neuropathy risk factors. Skin biopsy confirmed SFN in six, all of whom showed both neuropathy symptoms and signs, and two also showed autonomic dysfunction by autonomic function testing (AFT). Of the remaining seven patients who had normal skin biopsies, six showed no clinical neuropathy signs and one exhibited signs and had abnormal AFT. Two patients with markedly reduced intraepidermal nerve fiber densities and one with normal skin biopsy had severe and moderate coronavirus disease 2019 (COVID-19); the remainder experienced mild COVID-19 symptoms. Nine patients received symptomatic neuropathy treatment with paresthesias controlled in seven (77.8%). DISCUSSION: Our findings suggest that symptoms of SFN may develop during or shortly after COVID-19. SFN may underlie the paresthesias associated with long-haul post-COVID-19 symptoms.

Long-haul COVID: healthcare utilization and medical expenditures 6 months post-diagnosis.

BACKGROUND: Despite extensive evidence that COVID-19 symptoms may persist for up to a year, their long-term implications for healthcare utilization and costs 6 months post-diagnosis remain relatively unexplored. We examine patient-level association of COVID-19 diagnosis association of COVID-19 diagnosis with average monthly healthcare utilization and medical expenditures for up to 6 months, explore heterogeneity across age groups and determine for how many months post-diagnosis healthcare utilization and costs of COVID-19 patients persist above pre-diagnosis levels. METHODS: This population-based retrospective cohort study followed COVID-19 patients' healthcare utilization and costs from January 2019 through March 2021 using claims data provided by the COVID-19 Research Database. The patient population includes 250,514 individuals infected with COVID-19 during March-September 2020 and whose last recorded claim was not hospitalization with severe symptoms. We measure the monthly number and costs of total visits and by telemedicine, preventive, urgent care, emergency, immunization, cardiology, inpatient or surgical services and established patient or new patient visits. RESULTS: The mean (SD) total number of monthly visits and costs pre-diagnosis were .4783 (4.0839) and 128.06 (1182.78) dollars compared with 1.2078 (8.4962) visits and 351.67 (2473.63) dollars post-diagnosis. COVID-19 diagnosis associated with .7269 (95% CI, 0.7088 to 0.7449 visits; P < .001) more total healthcare visits and an additional $223.60 (95% CI, 218.34 to 228.85; P < .001) in monthly costs. Excess monthly utilization and costs for individuals 17 years old and under subside after 5 months to .070 visits and $2.77, persist at substantial levels for all other groups and most pronounced among individuals age 45-64 (.207 visits and $73.43) and 65 years or older (.133 visits and $60.49). CONCLUSIONS: This study found that COVID-19 diagnosis was associated with increased healthcare utilization and costs over a six-month post-diagnosis period. These findings imply a prolonged burden to the US healthcare system from medical encounters of COVID-19 patients and increased spending.

A novel conceptual model of trauma-informed care for patients with post-acute sequelae of SARS-CoV-2 illness (PASC).

AIM: This paper proposes a novel, trauma-informed, conceptual model of care for Post-Acute Sequelae of COVID-19 illness (PASC). DESIGN: This paper describes essential elements, linkages and dimensions of the model that affect PASC patient experiences and the potential impact of trauma-informed care on outcomes. DATA SOURCES: PASC is a consequence of the global pandemic, and a new disease of which little is known. Our model was derived from the limited available studies, expert clinical experience specific to PASC survivors and publicly available social media narratives authored by PASC survivors. IMPLICATIONS FOR NURSING: The model provides a critical and novel framework for the understanding and care of persons affected by PASC. This model is aimed at the provision of nursing care, with the intention of reducing the traumatic impacts of the uncertain course of this disease, a lack of defined treatment options and difficulties in seeking care. The use of a trauma-informed care approach to PASC patients can enhance nurses' ability to remediate and ameliorate both the traumatic burden of and the symptoms and experience of the illness. CONCLUSION: Applying a trauma-informed perspective to care of PASC patients can help to reduce the overall burden of this complex condition. Owing to the fundamentally holistic perspective of the nursing profession, nurses are best positioned to implement care that addresses multiple facets of the PASC experience. IMPACT: The proposed model specifically addresses the myriad ways in which PASC may affect physical as well as mental and psychosocial dimensions of health. The model particularly seeks to suggest means of supporting patients who have already experienced a life-threatening illness and are now coping with its long-term impact. Since the scope of this impact is not yet defined, trauma-informed care for PASC patients is likely to reduce the overall health and systems burdens of this complex condition.

Emerging Roles of Type-I Interferons in Neuroinflammation, Neurological Diseases, and Long-Haul COVID.

Interferons (IFNs) are pleiotropic cytokines originally identified for their antiviral activity. IFN-α and IFN-ß are both type I IFNs that have been used to treat neurological diseases such as multiple sclerosis. Microglia, astrocytes, as well as neurons in the central and peripheral nervous systems, including spinal cord neurons and dorsal root ganglion neurons, express type I IFN receptors (IFNARs). Type I IFNs play an active role in regulating cognition, aging, depression, and neurodegenerative diseases. Notably, by suppressing neuronal activity and synaptic transmission, IFN-α and IFN-ß produced potent analgesia. In this article, we discuss the role of type I IFNs in cognition, neurodegenerative diseases, and pain with a focus on neuroinflammation and neuro-glial interactions and their effects on cognition, neurodegenerative diseases, and pain. The role of type I IFNs in long-haul COVID-associated neurological disorders is also discussed. Insights into type I IFN signaling in neurons and non-neuronal cells will improve our treatments of neurological disorders in various disease conditions.

Antihistamines for Postacute Sequelae of SARS-CoV-2 Infection.

Postacute sequelae of SARS-CoV2 (PASC) infection is an emerging global health crisis, variably affecting millions worldwide. PASC has no established treatment. We describe 2 cases of PASC in response to opportune administration of over-the-counter antihistamines, with significant improvement in symptoms and ability to perform activities of daily living. Future studies are warranted to understand the potential role of histamine in the pathogenesis of PASC and explore the clinical benefits of antihistamines in the treatment of PASC.

MRI negative myelopathy post mild SARS-CoV-2 infection: vasculopathy or inflammatory myelitis?

Since the onset of the COVID-19 pandemic, there have been rare reports of spinal cord pathology diagnosed as inflammatory myelopathy and suspected spinal cord ischemia after SARS-CoV-2 infection. Herein, we report five cases of clinical myelopathy and myeloradiculopathy in the setting of post-COVID-19 disease, which were all radiographically negative. Unlike prior reports which typically characterized hospitalized patients with severe COVID-19 disease and critical illness, these patients typically had asymptomatic or mild-moderate COVID-19 disease and lacked radiologic evidence of structural spinal cord abnormality. This case series highlights that COVID-19 associated myelopathy is not rare, requires a high degree of clinical suspicion as imaging markers may be negative, and raises several possible pathophysiologic mechanisms.

Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)-A Systemic Review and Comparison of Clinical Presentation and Symptomatology.

Background and Objectives: Long COVID defines a series of chronic symptoms that patients may experience after resolution of acute COVID-19. Early reports from studies with patients with long COVID suggests a constellation of symptoms with similarities to another chronic medical illness-myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). A review study comparing and contrasting ME/CFS with reported symptoms of long COVID may yield mutualistic insight into the characterization and management of both conditions. Materials and Methods: A systemic literature search was conducted in MEDLINE and PsycInfo through to 31 January 2021 for studies related to long COVID symptomatology. The literature search was conducted in accordance with PRISMA methodology. Results: Twenty-one studies were included in the qualitative analysis. Long COVID symptoms reported by the included studies were compared to a list of ME/CFS symptoms compiled from multiple case definitions. Twenty-five out of 29 known ME/CFS symptoms were reported by at least one selected long COVID study. Conclusions: Early studies into long COVID symptomatology suggest many overlaps with clinical presentation of ME/CFS. The need for monitoring and treatment for patients post-COVID is evident. Advancements and standardization of long COVID research methodologies would improve the quality of future research, and may allow further investigations into the similarities and differences between long COVID and ME/CFS.

Orthostatic Symptoms and Reductions in Cerebral Blood Flow in Long-Haul COVID-19 Patients: Similarities with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Background and Objectives: Symptoms and hemodynamic findings during orthostatic stress have been reported in both long-haul COVID-19 and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), but little work has directly compared patients from these two groups. To investigate the overlap in these clinical phenotypes, we compared orthostatic symptoms in daily life and during head-up tilt, heart rate and blood pressure responses to tilt, and reductions in cerebral blood flow in response to orthostatic stress in long-haul COVID-19 patients, ME/CFS controls, and healthy controls. Materials and Methods: We compared 10 consecutive long-haul COVID-19 cases with 20 age- and gender-matched ME/CFS controls with postural tachycardia syndrome (POTS) during head-up tilt, 20 age- and gender-matched ME/CFS controls with a normal heart rate and blood pressure response to head-up tilt, and 10 age- and gender-matched healthy controls. Identical symptom questionnaires and tilt test procedures were used for all groups, including measurement of cerebral blood flow and cardiac index during the orthostatic stress. Results: There were no significant differences in ME/CFS symptom prevalence between the long-haul COVID-19 patients and the ME/CFS patients. All long-haul COVID-19 patients developed POTS during tilt. Cerebral blood flow and cardiac index were more significantly reduced in the three patient groups compared with the healthy controls. Cardiac index reduction was not different between the three patient groups. The cerebral blood flow reduction was larger in the long-haul COVID-19 patients compared with the ME/CFS patients with a normal heart rate and blood pressure response. Conclusions: The symptoms of long-haul COVID-19 are similar to those of ME/CFS patients, as is the response to tilt testing. Cerebral blood flow and cardiac index reductions during tilt were more severely impaired than in many patients with ME/CFS. The finding of early-onset orthostatic intolerance symptoms, and the high pre-illness physical activity level of the long-haul COVID-19 patients, makes it unlikely that POTS in this group is due to deconditioning. These data suggest that similar to SARS-CoV-1, SARS-CoV-2 infection acts as a trigger for the development of ME/CFS.

Baseline socioeconomic status predicting post-COVID-19 symptoms: Results from Isfahan COVID Cohort (ICC) study.

Objectives: Patients experience complications following their recovery from COVID-19, known as post-COVID-19. This study aimed to investigate the association between baseline socioeconomic status (SES) and post-COVID-19 symptoms among hospitalized and non-hospitalized patients. Methods: In the study, we used data from the Isfahan COVID Cohort (ICC) study, a 5-year longitudinal cohort study started from March 10, 2020. SES was measured using short form of SES questionnaire (SES-SQ), consisting of employment status, house room number, the number of trips taken, and using notebooks, laptop, or tablet in the house. Cox proportional hazard analysis was used to examine the association between baseline SES and post-COVID-19 symptoms including general, cardiovascular and respiratory systems, adjusting for potential confounders. Results: Out of the 3912 patients included in the study, 66.4 % reported post-COVID-19 symptoms. There was an association between low SES and increased risk of post-COVID-19 cardiovascular symptoms in the whole population (HR = 1.15; 95 CI, 1.01-1.31, p = 0.039). Considering the hospitalization status revealed that hospitalized patients with low SES had a higher risk of experiencing post-COVID-19 cardiovascular symptoms (HR = 1.96; 95 CI, 1.23-3.12, p = 0.004), while in non-hospitalized, low SES patients a lower risk was observed (HR = 0.82; 95 CI, 0.70-0.97, p = 0.017). No significant association was found between SES and other post-COVID-19 symptoms including general and respiratory symptoms. Conclusions: We concluded an association between higher SES and increased post-COVID-19 cardiovascular symptoms. Low SES was associated with higher risk of post-COVID-19 cardiovascular symptoms in hospitalized patients, while in non-hospitalized, it was associated with a lower risk.

The symptoms evolution of long COVID­19 (SE-LC19): a new patient-reported content valid instrument.

BACKGROUND: The field of long COVID research is rapidly evolving, however, tools to assess and monitor symptoms and recovery of the disease are limited. The objective of the present study was to develop a new patient-reported outcomes instrument, the Symptoms Evolution of Long COVID­19 (SE-LC19), and establish its content validity. METHODS: The 40-item SE-LC19 instrument was developed based on patient-relevant empirical evidence from scientific literature and clinical guidelines that reported symptoms specific to long COVID. A 2-part mixed-method approach was employed. Part 1: Qualitative interviews with a purposive sample of 41 patients with confirmed long COVID were conducted for the content validation of SE-LC19. During cognitive debriefing interviews, patients were asked to describe their understanding of the instrument's instructions, specific symptoms, response options, and recall period to ensure its relevance and comprehensiveness. Five clinicians of different medical specialties who regularly treated patients with long COVID were also interviewed to obtain their clinical expert opinions on SE-LC19. Part 2: Exploratory Rasch Measurement Theory (RMT) analysis was conducted to evaluate the psychometric properties of the SE-LC19 data collected during the interviews. RESULTS: Overall, patients reported that the instructions, questions, recall period, and response options for SE-LC19 were comprehensive and relevant. Minor conceptual gaps reported by patients captured nuances in the experience of some symptoms that could be considered in future studies. Some patients suggested a revision of the recall period from 24 h to 7 days to be able to capture more symptoms given the waxing and waning nature of some symptoms. Clinicians found the instrument comprehensive with minimal suggestions regarding its content. Exploratory RMT analyses provided evidence that the SE-LC19 questionnaire performed as intended. CONCLUSION: The present mixed-methods study in patients with confirmed long COVID supports the content validity and applicability of the SE-LC19 instrument to evaluate the symptoms of patients with long COVID. Further research is warranted to explore the psychometric properties of the instrument and refine a meaningful and robust patient-relevant endpoint for use in different settings such as clinical trials and clinical practice to track the onset, severity, and recovery of long COVID.

EHR-based Case Identification of Pediatric Long COVID: A Report from the RECOVER EHR Cohort.

Objective: Long COVID, marked by persistent, recurring, or new symptoms post-COVID-19 infection, impacts children's well-being yet lacks a unified clinical definition. This study evaluates the performance of an empirically derived Long COVID case identification algorithm, or computable phenotype, with manual chart review in a pediatric sample. This approach aims to facilitate large-scale research efforts to understand this condition better. Methods: The algorithm, composed of diagnostic codes empirically associated with Long COVID, was applied to a cohort of pediatric patients with SARS-CoV-2 infection in the RECOVER PCORnet EHR database. The algorithm classified 31,781 patients with conclusive, probable, or possible Long COVID and 307,686 patients without evidence of Long COVID. A chart review was performed on a subset of patients (n=651) to determine the overlap between the two methods. Instances of discordance were reviewed to understand the reasons for differences. Results: The sample comprised 651 pediatric patients (339 females, M age = 10.10 years) across 16 hospital systems. Results showed moderate overlap between phenotype and chart review Long COVID identification (accuracy = 0.62, PPV = 0.49, NPV = 0.75); however, there were also numerous cases of disagreement. No notable differences were found when the analyses were stratified by age at infection or era of infection. Further examination of the discordant cases revealed that the most common cause of disagreement was the clinician reviewers' tendency to attribute Long COVID-like symptoms to prior medical conditions. The performance of the phenotype improved when prior medical conditions were considered (accuracy = 0.71, PPV = 0.65, NPV = 0.74). Conclusions: Although there was moderate overlap between the two methods, the discrepancies between the two sources are likely attributed to the lack of consensus on a Long COVID clinical definition. It is essential to consider the strengths and limitations of each method when developing Long COVID classification algorithms.