Prevalence of Neuropathic Component in Post-COVID Pain Symptoms in Previously Hospitalized COVID-19 Survivors

Beyond the acute: pain in long COVID survivors at 1.5 years

OBJECTIVE

Long COVID, characterized by persistent symptoms post-acute COVID-19, remains a subject of intense investigation. This study focuses on pain, a common and notable symptom reported by long COVID patients.

METHOD

A cohort of 191 individuals, initially diagnosed with mild-to-moderate COVID-19, was followed up 1.5 years later to assess the frequency, clinical characteristics, and factors associated with pain persistence.

RESULTS

Our study revealed that 31.9% of participants experienced at least one persistent pain symptom after 1.5 years. Headache emerged as the most prevalent symptom (29.8%), followed by myalgia (5.8%) and neuropathic pain (4.2%). Factors such as female gender and the presence of neuropathic pain symptom were identified as predictors of long-term headaches. Myalgia, showed associations with headache, arthralgia, and low ferritin levels. Persistent neuropathic pain symptom (4.2%) was linked to older age, female gender, sore throat, and headache.

CONCLUSION

This study provides insights into the evolution of pain symptoms over time after COVID-19 infection, emphasizing the interconnection between different pain syndromes. This research contributes to understanding the diverse and evolving nature of pain in long COVID survivors, offering valuable insights for targeted interventions and further investigations into the underlying mechanisms of persistent pain.

Exploring viral neuropathic pain: Molecular mechanisms and therapeutic implications

As the Coronavirus Disease 2019 (COVID-19) pandemic continues, there is a growing concern regarding the relationship between viral infections and neuropathic pain. Chronic neuropathic pain resulting from virus-induced neural dysfunction has emerged as a significant issue currently faced. However, the molecular mechanisms underlying this phenomenon remain unclear, and clinical treatment outcomes are often suboptimal. Therefore, delving into the relationship between viral infections and neuropathic pain, exploring the pathophysiological characteristics and molecular mechanisms of different viral pain models, can contribute to the discovery of potential therapeutic targets and methods, thereby enhancing pain relief and improving the quality of life for patients. This review focuses on HIV-related neuropathic pain (HNP), postherpetic neuralgia (PHN), and neuropathic pain caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections, examining rodent models and relevant cellular molecular pathways. Through elucidating the connection between viral infections and neuropathic pain, it aims to delineate the current limitations and challenges faced by treatments, thereby providing insights and directions for future clinical practice and research.

COVID-19 and musculoskeletal pain: an overview of the current knowledge

The Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) has provoked billions of infections worldwide. Several meta-analyses have observed that up to 50% of individuals who had survived to a SARS-CoV-2 acute infection suffer from post-COVID symptoms lasting for weeks or months and up to one year after infection. The prevalence of post-COVID pain ranges between 10% to 20% when assessed with other overall post-COVID symptoms and can reach up to 50% to 60% when investigated specifically. The most common musculoskeletal manifestations of post-COVID-19 condition include fatigue, myalgia, arthralgia or back pain. Despite pain of musculoskeletal origin is one of the most prevalent post-COVID pain symptoms, the exact pathophysiological mechanisms of musculoskeletal post-COVID pain are not completely understood. Studies have reported the complexity of post-COVID pain including immune, biological, and psychological factors, and more recently, they have suggested that genetic and epigenetic factors may also play a potential role, highlighting the need for further investigation into these mechanisms. Its management is still controversial, as no specific guideline for treating musculoskeletal post-COVID pain has been proposed with only general consideration about the relevance of multidisciplinary and multimodal treatment approaches. In this paper we will highlight the clinical features, the mechanism, and the management possibilities of musculoskeletal post-COVID pain.

Evaluation and treatment approaches for neurological post-acute sequelae of COVID-19: A consensus statement and scoping review from the global COVID-19 neuro research coalition

Post-acute neurological sequelae of COVID-19 affect millions of people worldwide, yet little data is available to guide treatment strategies for the most common symptoms. We conducted a scoping review of PubMed/Medline from 1/1/2020-4/1/2023 to identify studies addressing diagnosis and treatment of the most common post-acute neurological sequelae of COVID-19 including: cognitive impairment, sleep disorders, headache, dizziness/lightheadedness, fatigue, weakness, numbness/pain, anxiety, depression and post-traumatic stress disorder. Utilizing the available literature and international disease-specific society guidelines, we constructed symptom-based differential diagnoses, evaluation and management paradigms. This pragmatic, evidence-based consensus document may serve as a guide for a holistic approach to post-COVID neurological care and will complement future clinical trials by outlining best practices in the evaluation and treatment of post-acute neurological signs/symptoms.

Precision management of post-COVID pain: An evidence and clinical-based approach

Background Pain after a SARS-CoV-2 acute infection (post-COVID pain) is becoming a new healthcare emergency but remains underestimated and most likely undertreated due to a lack of recognition of the phenomenon and knowledge of the underlying pain mechanisms. Evidence supporting any particular treatment approach for the management of post-COVID pain is lacking. Large variability in the patient response to any standard pain treatments is clinically observed, which has led to calls for a personalized, tailored approach to treating patients with chronic post-COVID pain (i.e. 'precision pain medicine'). Applying the global concerted action towards precision medicine to post-COVID pain could help guide clinical decision-making and aid in more effective treatments. Methods The current position paper discusses factors to be considered by clinicians for managing post-COVID pain ranging from identification of the pain phenotype to genetic consideration. Results The ability of clinicians to phenotype post-COVID pain into nociceptive, neuropathic, nociplastic or mixed type is suggested as the first step to better planification of a treatment programme. Further, the consideration of other factors, such as gender, comorbidities, treatments received at the acute phase of infection for onset-associated COVID-19 symptoms, factors during hospitalization or the presence of emotional disturbances should be implemented into a treatment programme. Conclusions Accordingly, considering these factors, management of post-COVID pain should include multimodal pharmacological and non-pharmacological modalities targeting emotional/cognitive aspects (i.e. psychological and/or coping strategies), central sensitization-associated mechanisms (i.e. pain neuroscience education), exercise programmes as well as lifestyle interventions (e.g. nutritional support and sleep management). SIGNIFICANCE: This position paper presents an evidence-based clinical reasoning approach for precision management of post-COVID pain.

Post-COVID Patients With New-Onset Chronic Pain 2 Years After Infection: Cross-Sectional Study

BACKGROUND

Although pain is common in non-hospitalized post-COVID-19 syndrome, only a few studies have provided information on the pain experience of these patients.

AIM

To identify the clinical and psychosocial profile associated with pain in non-hospitalized patients with post-COVID-19 syndrome.

METHOD

In this study there were three groups: healthy control group, successfully recovered group, and post-COVID syndrome group. Pain-related clinical profile and pain-related psychosocial variables were collected. Pain-related clinical profile included: pain intensity and interference (Brief Pain Inventory), central sensitization (Central Sensitization Scale), insomnia severity (Insomnia Severity Index), and pain treatment. Pain-related psychosocial variables were: fear of movement and (re)injury (Tampa Scale for Kinesiophobia), catastrophizing (Pain Catastrophizing Scale), depression, anxiety and stress (Depression, Anxiety and Stress Scale), and fear-avoidance beliefs (Fear Avoidance Beliefs Questionnaire).

RESULTS

In all, 170 participants were included in the study (healthy control group n = 58, successfully recovered group n = 57, and post-COVID syndrome group n = 55). Post-COVID syndrome group obtained significantly worse punctuation in pain-related clinical profile and psychosocial variables than the other two groups (p < .05).

CONCLUSIONS

In conclusion, patients with post-COVID-19 syndrome have experienced high pain intensity and interference, central sensitization, increased insomnia severity, fear of movement, catastrophizing, fear-avoidance beliefs, depression, anxiety, and stress.

Advances and challenges in neuropathic pain: a narrative review and future directions

Over the past few decades, substantial advances have been made in neuropathic pain clinical research. An updated definition and classification have been agreed. Validated questionnaires have improved the detection and assessment of acute and chronic neuropathic pain; and newer neuropathic pain syndromes associated with COVID-19 have been described. The management of neuropathic pain has moved from empirical to evidence-based medicine. However, appropriately targeting current medications and the successful clinical development of drugs acting on new targets remain challenging. Innovative approaches to improving therapeutic strategies are required. These mainly encompass rational combination therapy, drug repurposing, non-pharmacological approaches (such as neurostimulation techniques), and personalised therapeutic management. This narrative review reports historical and current perspectives regarding the definitions, classification, assessment, and management of neuropathic pain and explores potential avenues for future research.

Intractable Neuropathic Pain in COVID-19-Induced Guillain-Barré Syndrome: A Case Report

There is limited literature specific to neuropathic pain in coronavirus disease 2019 (COVID-19)-induced acute inflammatory demyelinating polyneuropathy (AIDP). We present a unique case of a 20-year-old vaccinated female with a past medical history of chronic hepatitis B virus and untreated anxiety who presented to the emergency department due to an intractable headache and horizontal diplopia in the setting of active COVID-19 infection. During acute hospitalization, the patient was diagnosed with the Miller-Fisher variant of Guillain-Barré syndrome (GBS), a disease with a known association with COVID-19. While in the ICU, the patient developed severe, 10/10-rated, distal, symmetric burning pain with associated allodynia requiring a multimodal regimen with combinations of intravenous narcotics, neuropathic medications, topical agents, and desensitization training to attempt to control her pain. Rehabilitation psychology was consulted while she was in chronic ventilatory rehabilitation for supplementation of behavioral pain management strategies with pharmacological approaches for continued pain. After several months and completion of a comprehensive inpatient rehabilitation program, the patient was weaned off intravenous narcotics and prescribed oral pain medications. This patient had the optimal response to amitriptyline, which likely aided in the co-treatment of psychological manifestations of COVID-19 and prolonged hospitalization. This study highlights the pathogenicity of COVID-19-induced AIDP, its potential severity, and the importance of a multidisciplinary approach to managing it.

Predicting model of mild and severe types of COVID-19 patients using Thymus CT radiomics model: A preliminary study

OBJECTIVE

To predict COVID-19 severity by building a prediction model based on the clinical manifestations and radiomic features of the thymus in COVID-19 patients.

METHOD

We retrospectively analyzed the clinical and radiological data from 217 confirmed cases of COVID-19 admitted to Xiangyang NO.1 People's Hospital and Jiangsu Hospital of Chinese Medicine from December 2019 to April 2022 (including 118 mild cases and 99 severe cases). The data were split into the training and test sets at a 7:3 ratio. The cases in the training set were compared in terms of clinical data and radiomic parameters of the lasso regression model. Several models for severity prediction were established based on the clinical and radiomic features of the COVID-19 patients. The DeLong test and decision curve analysis (DCA) were used to compare the performances of several models. Finally, the prediction results were verified on the test set.

RESULT

For the training set, the univariate analysis showed that BMI, diarrhea, thymic steatosis, anorexia, headache, findings on the chest CT scan, platelets, LDH, AST and radiomic features of the thymus were significantly different between the two groups of patients (P < 0.05). The combination model based on the clinical and radiomic features of COVID-19 patients had the highest predictive value for COVID-19 severity [AUC: 0.967 (OR 0.0115, 95%CI: 0.925-0.989)] vs. the clinical feature-based model [AUC: 0.772 (OR 0.0387, 95%CI: 0.697-0.836), P < 0.05], laboratory-based model [AUC: 0.687 (OR 0.0423, 95%CI: 0.608-0.760), P < 0.05] and model based on CT radiomics [AUC: 0.895 (OR 0.0261, 95%CI: 0.835-0.938), P < 0.05]. DCA also confirmed the high clinical net benefits of the combination model. The nomogram drawn based on the combination model could help differentiate between the mild and severe cases of COVID-19 at an early stage. The predictions from different models were verified on the test set.

CONCLUSION

Severe cases of COVID-19 had a higher level of thymic involution. The thymic differentiation in radiomic features was related to disease progression. The combination model based on the radiomic features of the thymus could better promote early clinical intervention of COVID-19 and increase the cure rate.

Symptom Experience and Perceived Health Status of People With Long COVID in Thailand

Introduction

Despite the World Health Organization declaring COVID-19 no longer a public health emergency, reports of long COVID persist globally, raising concerns about its impact on individuals.

Objective

This retrospective study aimed to explore the symptom experiences of individuals with long COVID-19 and examine the relationship between those experiences and perceived negative health status in Thailand.

Methods

The study focused on individuals with moderate to severe COVID-19 infections. Between July 3, 2022 and December 1, 2022, we conducted telephone interviews with 86 individuals who tested positive for SARS-CoV-2 and received outpatient care in Bangkok. The COVID-19 Yorkshire Rehabilitation Screening was utilized to measure symptom occurrence, duration, severity, and health status on an 11-point numerical rating scale from 0 (none or excellent) to 10 (the worst). A Spearman rank correlation was used to analyze the relationships between long COVID symptoms and negative perception of health status.

Results

Among the participants, 75.6% had long COVID, with a median of three symptoms lasting for a median duration of 5.6 months. Difficulties in performing daily activities were most common, reported by 50.8% of participants. The majority (80.0%) experienced itching, headache, cognition, muscle pain, continence, and sleeping problem for 6 months. Loss of taste was the most severe symptom, with a mean severity rating of 8.8. There were significant positive relations between a negative perception of health status and multiple symptoms, symptom severity, functional disability, and additional symptoms.

Conclusion

Individuals with moderate to severe COVID-19 infection who experienced long COVID had poorer perceived health status. To effectively manage and improve the health status of individuals with long COVID, nurses should provide follow-up care, assess not only the occurrence of symptoms but also their duration and severity, and evaluate performance outcomes.

A systematic review and meta-analysis of neuropathic pain associated with coronavirus disease 2019

BACKGROUND AND OBJECTIVE

Neuropathic pain is an occasionally reported complication of coronavirus disease 2019 (COVID-19) that has received increased attention in scientific literature. In this systematic review and meta-analysis, we aimed to provide information on the frequency of neuropathic pain associated with COVID-19.

DATABASES AND DATA TREATMENT

We systematically reviewed and analysed literature regarding neuropathic pain associated with COVID-19. Literature searches were conducted in PubMed, EMBASE and Cochrane Library databases. We considered prospective and retrospective studies published up until September 2022 (limitations included English language, full-text publications and studies including at least 10 patients). A random effects meta-analysis was performed and heterogeneity and publication bias were assessed.

RESULTS

We identified 149 studies. We included 17 studies in the systematic review, and six studies reporting the frequency of neuropathic pain in the acute/subacute phase of COVID-19 in the meta-analysis. The estimated frequency of neuropathic pain ranged between 0.4 and 25%. Forest plot analysis showed that the random effect overall frequency was 10% (95% confidence interval: 5%-15%), with a high level of heterogeneity (Chi²  = 104; Tau²  = 0.004; df = 5; I²  = 95%; test for overall effect: Z = 3.584; p < 0.0005). The overall risk of bias was moderate in all studies selected, particularly due to the poor description of neuropathic pain diagnostic criteria.

CONCLUSIONS

The pooled estimated frequency of neuropathic pain associated with COVID-19 should be considered with caution due to the high heterogeneity across studies and the poor description of the neuropathic pain diagnostic criteria applied.

SIGNIFICANCE

Emerging evidence supports the development of neuropathic pain as a complication of COVID-19. However, longitudinal studies enrolling consecutive patients with COVID-19 that detail the diagnostic criteria for neuropathic pain are needed to better assess the frequency of this condition.

Data-Driven Path Analytic Modeling to Understand Underlying Mechanisms in COVID-19 Survivors Suffering from Long-Term Post-COVID Pain: A Spanish Cohort Study

Pain can be present in up to 50% of people with post-COVID-19 condition. Understanding the complexity of post-COVID pain can help with better phenotyping of this post-COVID symptom. The aim of this study is to describe the complex associations between sensory-related, psychological, and cognitive variables in previously hospitalized COVID-19 survivors with post-COVID pain, recruited from three hospitals in Madrid (Spain) by using data-driven path analytic modeling. Demographic (i.e., age, height, and weight), sensory-related (intensity or duration of pain, central sensitization-associated symptoms, and neuropathic pain features), psychological (anxiety and depressive levels, and sleep quality), and cognitive (catastrophizing and kinesiophobia) variables were collected in a sample of 149 subjects with post-COVID pain. A Bayesian network was used for structural learning, and the structural model was fitted using structural equation modeling (SEM). The SEM model fit was excellent: RMSEA < 0.001, CFI = 1.000, SRMR = 0.063, and NNFI = 1.008. The only significant predictor of post-COVID pain was the level of depressive symptoms (β=0.241, p = 0.001). Higher levels of anxiety were associated with greater central sensitization-associated symptoms by a magnitude of β=0.406 (p = 0.008). Males reported less severe neuropathic pain symptoms (−1.50 SD S-LANSS score, p < 0.001) than females. A higher level of depressive symptoms was associated with worse sleep quality (β=0.406, p < 0.001), and greater levels of catastrophizing (β=0.345, p < 0.001). This study presents a model for post-COVID pain where psychological factors were related to central sensitization-associated symptoms and sleep quality. Further, maladaptive cognitions, such as catastrophizing, were also associated with depression. Finally, females reported more neuropathic pain features than males. Our data-driven model could be leveraged in clinical trials investigating treatment approaches in COVID-19 survivors with post-COVID pain and can represent a first step for the development of a theoretical/conceptual framework for post-COVID pain.

Phenotyping Post-COVID Pain as a Nociceptive, Neuropathic, or Nociplastic Pain Condition

Pain after an acute Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) condition (post-COVID pain) is becoming a new healthcare emergency. Precision medicine refers to an evidence-based method of grouping patients based on their diagnostic/symptom presentation and then tailoring specific treatments accordingly. Evidence suggests that post-COVID pain can be categorized as nociceptive (i.e., pain attributable to the activation of the peripheral receptive terminals of primary afferent neurons in response to noxious chemical, mechanical, or thermal stimuli), neuropathic (i.e., pain associated with a lesion or disease of the somatosensory nervous system and limited to a "neuroanatomically plausible" distribution of the system), nociplastic (i.e., pain arising from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain), or mixed type (when two pain phenotypes co-exist). Each of these pain phenotypes may require a different treatment approach to maximize treatment effectiveness. Accordingly, the ability to classify post-COVID pain patients into one of these phenotypes would likely be critical for producing successful treatment outcomes. The 2021 International Association for the Study of Pain (IASP) clinical criteria and grading system provide a framework for classifying pain within a precision pain medicine approach. Here we present data supporting the possibility of grouping patients with post-COVID pain into pain phenotypes, using the 2021 IASP classification criteria, with a specific focus on nociplastic pain, which is probably the primary mechanism involved in post-COVID pain. Nociplastic pain, which is usually associated with comorbid symptomology (e.g., poor sleep quality, fatigue, cognitive-emotional disturbances, etc.) and is considered to be more difficult to treat than other pain types, may require a more nuanced multimodal treatment approach to achieve better treatment outcomes.

Treatments for kinesiophobia in people with chronic pain: A scoping review

Kinesiophobia is associated with pain intensity in people suffering from chronic pain. The number of publications highlighting this relationship has increased significantly in recent years, emphasizing the importance of investigating and synthesizing research evidence on this topic. The purpose of this scoping review was to answer the following questions: (1) What types of interventions have been or are currently being studied in randomized controlled trials (RCTs) for the management of kinesiophobia in patients with chronic pain? (2) What chronic pain conditions are targeted by these interventions? (3) What assessment tools for kinesiophobia are used in these interventions? According to the studies reviewed, (1) physical exercise is the most commonly used approach for managing irrational fear of movement, (2) interventions for kinesiophobia have primarily focused on musculoskeletal pain conditions, particularly low back pain and neck pain, and (3) the Tampa Scale of Kinesiophobia is the most commonly used tool for measuring kinesiophobia. Future RCTs should consider multidisciplinary interventions that can help patients confront their irrational fear of movement while taking into account the patient’s personal biological, psychological, and social experiences with pain and kinesiophobia.

Pain Extent Is Not Associated with Sensory-Associated Symptoms, Cognitive or Psychological Variables in COVID-19 Survivors Suffering from Post-COVID Pain

We aimed to investigate the relationship between pain extent, as a sign of sensitization, and sensory-related, cognitive and psychological variables in hospitalized COVID-19 survivors with post-COVID pain. One hundred and forty-six (67 males, 79 females) previously hospitalized COVID-19 survivors with post-COVID pain completed demographic (age, sex, height, weight), sensory-related (Central Sensitization Inventory, Self-Report Leeds Assessment of Neuropathic Symptoms), cognitive (Pain Catastrophizing Scale, Tampa Scale for Kinesiophobia) and psychological (Hospital Anxiety and Depression Scale, Pittsburgh Sleep Quality Index) variables. Pain extent and frequency maps were calculated from pain drawings using customized software. After conducting a correlation analysis to determine the relationships between variables, a stepwise linear regression model was performed to identify pain extent predictors, if available. Pain extent was significantly and weakly associated with pain intensity (r = -0.201, p = 0.014): the larger the pain extent, the lower the pain intensity. No other significant association was observed between pain extent and sensory-related, cognitive, or psychological variables in individuals with post-COVID pain. Females had higher pain intensity, more sensitization-associated symptoms, higher anxiety, lower sleep quality, and higher kinesiophobia levels than males. Sex differences correlation analyses revealed that pain extent was associated with pain intensity in males, but not in females. Pain extent was not associated with any of the measured variables and was also not related to the presence of sensitization-associated symptoms in our sample of COVID-19 survivors with long-term post-COVID pain.

The Self-Reported Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and PainDETECT Questionnaires in COVID-19 Survivors with Post-COVID Pain

This study aimed to analyze correlations between Self-Report Leeds Assessment of Neuropathic Symptoms (S-LANSS) and PainDETECT with proxies of sensitization, pain-related, or psychological/cognitive variables in coronavirus disease, 2019 (COVID-19) survivors exhibiting post-COVID pain. Demographic, clinical, psychological, cognitive, sensitization-associated symptoms, and health-related quality of life were collected in 146 survivors with post-COVID pain. The PainDETECT and S-LANSS questionnaires were used for assessing neuropathic pain-related symptoms. Patients were assessed with a mean of 18.8 (SD 1.8) months after hospitalization. Both questionnaires were positively associated with pain intensity (p < 0.05), anxiety (PainDETECT p < 0.05; S-LANSS p < 0.01), sensitization-associated symptoms (p < 0.01), catastrophism (p < 0.01), and kinesiophobia (p < 0.01) and negatively associated with quality of life (PainDETECT p < 0.05; S-LANSS p < 0.01). Depressive levels were associated with S-LANSS (p < 0.05) but not with PainDETECT. The stepwise regression analyses revealed that 47.2% of S-LANSS was explained by PainDETECT (44.6%), post-COVID pain symptoms duration (1.7%), and weight (1.1%), whereas 51.2% of PainDETECT was explained by S-LANSS (44.6%), sensitization-associated symptoms (5.4%), and anxiety levels (1.2%). A good convergent association between S-LANSS and PainDETECT was found. Additionally, S-LANSS was associated with symptom duration and weight whereas PainDETECT was associated with sensitization-associated symptoms and anxiety levels, suggesting that the two questionnaires evaluate different aspects of the neuropathic pain spectrum in post-COVID pain patients.

Understanding Sensitization, Cognitive and Neuropathic Associated Mechanisms behind Post-COVID Pain: A Network Analysis

This study aimed to describe a network including demographic, sensory-related, psychological/cognitive and other variables in individuals with post-COVID pain after hospitalization. Demographic (i.e., age, height, weight, months with symptoms), sensory-related (Central Sensitization Inventory -CSI-, Self-Report Leeds Assessment of Neuropathic Symptoms -S-LANSS-, PainDETECT), psychological/cognitive (Hospital Anxiety and Depression Scale -HADS-A/HADS-D-, Pain Catastrophizing Scale -PCS-, Tampa Scale for Kinesiophobia -TSK-11-) and other (sleep quality and health-related quality of life -EQ/5D/5L) variables were collected in 146 COVID-19 survivors with post-COVID pain. A network analysis was conducted to quantify the adjusted correlations between the modelled variables, and to assess their centrality indices (i.e., the connectivity with other symptoms in the network and the importance in the system modelled as network). The network revealed associations between sensory-related and psychological/cognitive variables. PainDETECT was associated with S-LANSS (ρ: 0.388) and CSI (ρ: 0.207). Further, CSI was associated with HADS-A (ρ: 0.269), TSK-11 (ρ: 0.165) and female gender (ρ: 0.413). As expected, HADS-A was associated with HADS-D (ρ: 0.598) and TSK-11 with PCS (ρ: 0.405). The only negative association was between sleep quality and EQ-5D-5L (ρ: -0.162). Gender was the node showing the highest strength, closeness, and betweenness centralities. In addition, CSI was the node with the second highest closeness and betweenness centralities, whereas HADS-D was the node with the second highest strength centrality. This is the first study applying a network analysis for phenotyping post-COVID pain. Our findings support a model where sensitization-associated symptoms, neuropathic phenotype, and psychological aspects are connected, reflecting post-COVID pain as a nociplastic pain condition. In addition, post-COVID pain is gender dependent since female sex plays a relevant role. Clinical implications of current findings, e.g., developing treatments targeting these mechanisms, are discussed.

Sensitization-Associated Post-COVID-19 Symptoms at 6 Months Are Not Associated with Serological Biomarkers at Hospital Admission in COVID-19 Survivors: A Secondary Analysis of a Cohort Study

Individuals who survived coronavirus disease, 2019 (COVID-19), often have symptoms of sensitization, but the extent to which these symptoms relate to serological biomarkers remains unclear. Therefore, this secondary analysis evaluated the association between serological biomarkers at hospital admission with sensitization-associated post-COVID-19 symptoms in a sample of previously hospitalized COVID-19 survivors. Sixty-seven individuals hospitalized due to SARS-CoV-2 infection in one urban hospital of Madrid (Spain) during the first wave of the pandemic were assessed a mean of 6.0 (SD 0.8) months after hospital discharge. The Central Sensitization Inventory (CSI) was used as rough tool to estimate the presence of sensitization-associated post-COVID-19 symptoms (≥40/100 points). Levels of 16 serological biomarkers collected at hospital admission were obtained from medical records. Twenty-four (35.8%) patients reported sensitization-associated post-COVID-19 symptoms (CSI ≥ 40 points). Subjects reporting sensitization-associated symptoms had lower ferritin and hemoglobin levels than those not reporting sensitization-associated post-COVID-19 symptoms; however, these differences were small. We observed significant but small negative associations of the CSI score with ferritin (r: -0.251, p = 0.04) and hemoglobin (r: -0.292, p = 0.017) levels. No other significant difference was found. In conclusion, this secondary analysis did not find significant associations between the investigated serological biomarkers at hospital admission and sensitization-associated post-COVID-19 symptoms at 6 months after hospitalization in COVID-19 survivors.