Serial Changes of Long COVID Symptoms and Clinical Utility of Serum Antibody Titers for Evaluation of Long COVID

Clinical characteristics of female long COVID patients with menstrual symptoms: a retrospective study from a Japanese outpatient clinic

PURPOSE

To elucidate the impact of long COVID on menstruation and mental health, medical records of patients with long COVID were evaluated.

METHODS

Symptoms of long COVID, QOL, mental health, and related endocrine data were compared between two groups with and without menstrual disturbances.

RESULTS

Of 349 female patients who visited our clinic between February 2021 and March 2023, 223 patients with long COVID (aged 18-50 years) were included. Forty-four (19.7%) of the patients had menstrual symptoms associated with long COVID. The patients with menstrual symptoms were older than those without menstrual symptoms (42.5 vs. 38 years). The percentage of patients with menstrual symptoms was higher during the Omicron phase (24%) than during the Preceding (13%) and Delta (12%) phases. Cycle irregularity was the most frequent (in 63.6% of the patients), followed by severe pain (25%), heavy bleeding (20.5%), perimenopausal symptoms (18.2%), and premenstrual syndrome (15.9%). Fatigue and depression were the most frequent complications. Scores for fatigue and for QOL were significantly worse in long COVID patients with menstrual symptoms. Results of endocrine examinations showed significantly increased cortisol levels in patients with menstrual complaints.

CONCLUSION

Long COVID has an impact on menstrual conditions and on QOL related to menstrual conditions.

Symptoms of post COVID-19 condition and diseases/conditions diagnosed after COVID-19 in Japanese patients: A real-world study using a claims database

BACKGROUND

More than 200 symptoms of post coronavirus disease (COVID-19) condition (PCC) impacting patients' quality of life have been reported. This study describes the symptoms of well-known PCC and diseases/conditions diagnosed after COVID-19 and analyzes the trends in well-known PCC according to the epidemic waves in the Japanese population.

METHODS

Patients with a COVID-19 diagnosis in the JMDC claims database were matched 1:1 with individuals without COVID-19 diagnosis (controls) based on sex, year and month of birth, and risk factors for aggravation. The first month of COVID-19 diagnosis from January 2020-March 2022 was the index month, and the observation period was from July 2019 to 6 months from the index month (patients) and July 2019-September 2022 (controls).

RESULTS

Of 263,456 each of patients and controls after matching, 51.8 % were aged 18-49 years, 56.3 % were male, and 24.5 % had risk factors for aggravation. One in 18 patients experienced well-known PCC 2-3 months after severe acute respiratory syndrome cornonavirus 2 infection, with the highest odds ratio (OR) being for pulmonary thromboembolism (29.37), followed by smell/taste disorder (13.34) and respiratory failure (8.28). Some of the common diseases/conditions diagnosed after COVID-19 comprised those of the genitourinary system, eye and adnexa, and ear and mastoid process and certain infectious and parasitic diseases. Overall, the risk difference decreased from the first to the sixth wave, but the OR was >1.00 for most symptoms even during the sixth wave.

CONCLUSIONS

PCC symptoms showed a declining trend over time but persisted. Physicians and patients need to recognize PCC symptoms.

Knowledge, Attitudes, and Practices Among Community Populations Toward Long COVID in China

Purpose

This study aimed to assess the knowledge, attitudes and practices (KAP) among community populations toward Long COVID.

Patients and Methods

This cross-sectional study was conducted between March 2023 and June 2023 at the Ordos Mongolian hospital and Ordos Central Hospital in Ordos, Inner Mongolia, China, employing a self-designed questionnaire to collect demographic data from community populations and evaluate their knowledge, attitudes, and practices toward Long COVID.

Results

A total of 591 participants were enrolled in this study. Among them, 343 (58.04%) were female and 317 (53.64%) aged 40 to 59 years. The mean knowledge, attitudes and practices scores were 6.02±1.19 (possible range: 0-7), 26.83±2.96 (possible range: 7-35), and 45.91±7.20 (possible range: 11-55), respectively. The Pearson's correlation analysis indicated significant positive correlations between knowledge and attitudes (r=0.210, P<0.001), and attitudes and practices (r=0.476, P<0.001). The structural equation model demonstrated that knowledge positively affect attitudes, as indicated by a path coefficient of 1.028 (P<0.001), and attitudes positively affect practices, with a path coefficient of 0.817 (P<0.001).

Conclusion

Although our findings indicate that community populations generally have adequate knowledge, active attitudes, and proactive practices regarding Long COVID, there is still a need for healthcare providers to further enhance Long COVID awareness in the community. This involves fostering positive attitudes through open communication, emphasizing the importance of early intervention and treatment adherence, and encouraging continued adherence to preventive measures.

Patient and Immunological Factors Associated With Delayed Clearance of Mucosal Severe Acute Respiratory Syndrome Coronavirus 2 RNA and Symptom Persistence

Serial blood and mucosal samples were characterized for 102 participants enrolled a median of 7.0 days after coronavirus disease 2019 diagnosis. Mucosal RNA was detectable for a median of 31.5 (95% confidence interval [CI], 20.5-63.5) days, with persistence ≥1 month associated with obesity (body mass index [BMI] ≥30 kg/m2; odds ratio [OR], 3.9 [95% CI, 1.2-13.8]) but not age, sex, or chronic conditions. Fifteen participants had likely reinfection; lower serum anti-spike IgG levels were associated with reinfection risk. Nearly half of participants (47%) reported symptoms lasting ≥2-3 months; persistence ≥3 months was associated with BMI ≥30 kg/m2 (OR, 4.2 [95% CI, 1.1-12.8]) and peak anti-spike and anti-nucleocapsid antibody levels.

Importance of Blood Glucose Measurement for Predicting the Prognosis of Long COVID: A Retrospective Study in Japan

Purpose: The present study aimed to clarify the effects of a hyperglycemic condition on the clinical consequences of long COVID. Methods: Among 643 patients who visited the outpatient clinic of our hospital from February 2021 to September 2023, long COVID patients were classified into a hyperglycemic (HG) group with casual blood glucose levels above 140 mg/dL and a normoglycemic (NG) group. The patients' backgrounds, clinical symptoms, health status including the QOL evaluation scale (EQ-5D-5L), self-rating depression scale (SDS), and F-scale questionnaire (FSSG), blood test data, and recovery periods were analyzed. Results: The NG group included 607 patients with long COVID and the HG group included 36 patients with long COVID. Patients in the HG group were older than those in the NG group (55 vs. 41 years; p < 0.001) and included a larger percentage of males (67% vs. 44%; p = 0.009). The HG group had a larger percentage of patients with moderate-to-severe conditions in the acute infection phase (28% vs. 12%; p = 0.008), a higher BMI (25 vs. 22 kg/m2; p < 0.001), higher blood pressure (138/81 vs. 122/72 mmHg; p < 0.001), and a larger percentage of patients with an alcohol drinking habit (53% vs. 34%; p = 0.031). Long COVID symptoms and self-rated scales were not differed between the two groups; however, the laboratory data showed that liver and renal functions and metabolic data were significantly worse in the HG group. Although there was no apparent difference between the two groups in duration from the infection to the first visit, the HG group had a significantly longer period of recovery from long COVID (median period of 421 vs. 294 days; p = 0.019). Conclusion: A hyperglycemic state associated with other lifestyle-related diseases is associated with the prolongation of recovery from long COVID.

Changes in Working Situations of Employed Long COVID Patients: Retrospective Study in Japanese Outpatient Clinic

Purpose: The present study aimed to uncover the impact of long COVID on the working situations of Japanese patients. Methods: Changes in the working situations of the patients who visited our long COVID clinic were evaluated from medical records for the aspects of physical status, quality of life (QOL), and mental conditions. Results: Of 846 long COVID patients who visited our clinic from February 2021 to December 2023, 545 employed patients aged between 18 and 65 years were included in this study. A total of 295 patients (54.1%) with long COVID (median age: 43 years, female: 55.6%) experienced changes in their working status. Those patients included 220 patients (40.4%) who took a leave of absence, 53 patients (9.7%) who retired, and 22 patients (4%) with reduced working hours. Most of the patients (93.2%) with changes in working conditions had mild disease severity in the acute phase of COVID-19. The majority of those patients with mild disease severity (58.8%) were infected in the Omicron-variant phase and included 65.3% of the female patients. The major symptoms in long COVID patients who had changes in their working situations were fatigue, insomnia, headache, and dyspnea. Scores indicating fatigue and QOL were worsened in long COVID patients who had changes in their working situations. In addition, 63.7% of the long COVID patients with changes in their working situations had decreases in their incomes. Conclusions: Changes in the working situation of long COVID patients who were employed had a negative impact on the maintenance of their QOL.

Serial evaluation of antibody titres in patients recovered from COVID-19 and their correlation with disease severity

On March 11, 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. According to the findings of various studies conducted around the world, the serological response varies greatly among different populations, with the determinants of variable response still unknown, including the role of disease severity, which is thought to have a definite correlation. The purpose of this study was to assess serial SARS-CoV-2 IgG antibody response in COVID-19 patients and correlate it with disease severity. It was a longitudinal observational study in which 45 patients (age >18 yrs), were enrolled who had recovered from COVID-19 and were reporting to the post-COVID Care OPD Clinic. Patients who had been on long-term immunosuppressive therapy prior to SARS-CoV-2 infection were not eligible. All patients had not been immunized against SARS-CoV-2 and had no history of contact with recent COVID-19 cases. The patients underwent serial blood tests to determine serum IgG titers specific for SARS-CoV-2 at 30, 60, and 90 days after being diagnosed with COVID-19. Chemiluminescence was used to perform a semi-quantitative evaluation of the SARS-CoV-2 IgG antibody. At 30 days after confirmed SARS-CoV-2 infection, 98.78% had detectable serum IgG levels, and sero-reversion (loss of previously detectable antibodies) occurred in 2.5% at 60 days and 90 days. Serum IgG was found to peak at 30 days out of the three time points of measurement (30, 60, and 90 days from diagnosis). Serum IgG levels at 90 days were significantly lower than those at 30 days (p<0.0001) and 60 days (p=0.002). The current study's findings shed light on the presence and persistence of serum SARS-CoV-2-specific IgG antibodies following a natural infection. The findings point to a long-lasting immune response with increasing severity of initial COVID-19 disease.

15-month post-COVID syndrome in outpatients: Attributes, risk factors, outcomes, and vaccination status - longitudinal, observational, case-control study

Background

While the short-term symptoms of post-COVID syndromes (PCS) are well-known, the long-term clinical characteristics, risk factors and outcomes of PCS remain unclear. Moreover, there is ongoing discussion about the effectiveness of post-infection vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) to aid in PCS recovery.

Methods

In this longitudinal and observational case-control study we aimed at identifying long-term PCS courses and evaluating the effects of post-infection vaccinations on PCS recovery. Individuals with initial mild COVID-19 were followed for a period of 15 months after primary infection. We assessed PCS outcomes, distinct symptom clusters (SC), and SARS-CoV-2 immunoglobulin G (IgG) levels in patients who received SARS-CoV-2 vaccination, as well as those who did not. To identify potential associating factors with PCS, we used binomial regression models and reported the results as odds ratios (OR) with 95% confidence intervals (95%CI).

Results

Out of 958 patients, follow-up data at 15 month after infection was obtained for 222 (23.2%) outpatients. Of those individuals, 36.5% (81/222) and 31.1% (69/222) were identified to have PCS at month 10 and 15, respectively. Fatigue and dyspnea (SC2) rather than anosmia and ageusia (SC1) constituted PCS at month 15. SARS-CoV-2 IgG levels were equally distributed over time among age groups, sex, and absence/presence of PCS. Of the 222 patients, 77.0% (171/222) were vaccinated between 10- and 15-months post-infection, but vaccination did not affect PCS recovery at month 15. 26.3% of unvaccinated and 25.8% of vaccinated outpatients improved from PCS (p= .9646). Baseline headache (SC4) and diarrhoea (SC5) were risk factors for PCS at months 10 and 15 (SC4: OR 1.85 (95%CI 1.04-3.26), p=.0390; SC5: OR 3.27(95%CI 1.54-6.64), p=.0009).

Conclusion

Based on the specific symptoms of PCS our findings show a shift in the pattern of recovery. We found no effect of SARS-CoV-2 vaccination on PCS recovery and recommend further studies to identify predicting biomarkers and targeted PCS therapeutics.

Trends in Long COVID Symptoms in Japanese Teenage Patients

Background: Since the start of the global pandemic of coronavirus disease 2019 (COVID-19), not only adults but also many children have suffered from it. However, the clinical characteristics of long COVID in children remain unclear. Methods: In this retrospective observational study conducted in a single facility, we reviewed the medical records of all long COVID patients who visited Okayama University Hospital from February 2021 to October 2022, and we compared the clinical characteristics of long COVID in teenagers (11 to 18 years of age) with those in adults. Results: Data for 452 long COVID patients including 54 teenagers (11.9%) were analyzed. Fatigue was the most frequent symptom in teenagers (55.6% of the patients) and also in adults. On the other hand, the percentage of teenagers who complained of headache, which was the second most frequent complaint, was significantly higher than the percentage of adults (35.2% vs. 21.9%, p < 0.05). A comparison of the frequencies of symptoms depending on the viral variant showed that fatigue and headache were predominant symptoms in the Omicron variant phase. Of the 50 teenagers who were enrolled in schools, 28 (56.0%) could not attend school due to long COVID symptoms. The most common symptoms as reasons for absence from school were fatigue (85.7% of the patients), headache (42.9%), and insomnia (32.1%). Conclusions: Attention should be paid to the symptoms of fatigue and headache in teenagers with long COVID.

Characteristics of Sleep Disturbance in Patients with Long COVID: A Retrospective Observational Study in Japan

OBJECTIVES

The objective of this study was to determine the clinical and endocrinological features of sleep disturbance in patients with long COVID.

METHODS

This study was a single-center retrospective observational study for patients who visited the COVID-19 aftercare outpatient clinic (CAC) established in Okayama University Hospital in Japan during the period from 15 February 2021 to 29 July 2022. The long COVID patients were divided into two groups based on the presence or absence of sleep disturbance, and the clinical and laboratory characteristics of the patients were analyzed.

RESULTS

Out of 363 patients with long COVID, after excluding 6 patients, 60 patients (16.5%) (55% males, median age of 38 years) complaining of sleep disturbance were compared with 303 patients (83.5%) (43% males, median age of 40 years) without sleep-related symptoms. Although there were no significant differences in clinical backgrounds and severities of COVID-19 between the two groups by the multivariate analysis, the percentage of long COVID patients with sleep disturbance was significantly increased among patients infected in the Omicron-dominant phase. In addition, the prevalence rate of sleep disturbance in patients when infected in the Omicron phase (24.8%) was two-times higher than that in patients infected in the Delta phase (12.8%). Of note, the percentages of patients with sleep disturbance who also complained of general fatigue, headache, concentration loss, anxiety, low-grade fever, and brain fog symptoms were higher than the percentages of patients without sleep disturbance who had the same complaints. Among the types of sleep disturbance, the percentage of patients who complained of loss of sleep induction (75%) was much higher than the percentage of patients with early-awakening sleep disturbance (6.7%), and many of the patients with mid-awakening types of insomnia had brain fog symptoms. Endocrine examinations revealed that long COVID patients with sleep disturbance had significantly higher levels of plasma adrenocorticotropin and lower levels of serum growth hormone, suggesting the presence of hypothalamic-pituitary stress.

CONCLUSION

The prevalence of sleep disturbance has been increasing in long COVID patients infected in the Omicron phase with a certain clinical and endocrine trend.

Hormonal trends in patients suffering from long COVID symptoms

Symptoms of long COVID are complex and long-lasting, and endocrine dysfunction might be involved in the underlying mechanisms. In this study, to clarify the hormonal characteristics of long COVID patients, laboratory data for patients who visited the outpatient clinic for long COVID were evaluated. A retrospective analysis was performed for patients who visited Okayama University Hospital during the period from Feb 2021 to Dec 2021 with focus on the interrelationships between major symptoms and endocrine data. Information and laboratory data were obtained from medical records for 186 patients. The patients had various symptoms, and the most frequent symptoms were general malaise, dysosmia/dysgeusia, hair loss, headache, dyspnea, and sleeplessness. Patients who were suffering from fatigue and dysosmia/dysgeusia were younger, while hair loss was more frequent in older and female patients. As for the characteristics of patients suffering from general fatigue, the scores of depression and fatigue were positively correlated with serum levels of cortisol and free thyroxin (FT4), respectively. Also, patients suffering from general fatigue had lower levels of serum growth hormone and higher levels of serum FT4, while patients with dysosmia/dysgeusia had a significantly lower level of serum cortisol. Serum thyrotropin (TSH) levels were higher and the ratios of FT4/TSH were lower in the initially severe cases, suggesting occult hypothyroidism. In addition, the ratios of plasma adrenocorticotropin to serum cortisol were decreased in patients with relatively high titers of serum SARS-CoV-2 antibody. Thus, hormonal changes seem to be, at least in part, involved in the persistent symptoms of long COVID.

Transitional Changes in Fatigue-Related Symptoms Due to Long COVID: A Single-Center Retrospective Observational Study in Japan

Background and Objectives: Changes in post COVID-19 condition (PCC) characteristics caused by viral variants have yet to be clarified. We aimed to characterize the differences between clinical backgrounds and manifestations in long COVID patients who were infected with the Delta variant and those who were infected with the Omicron variants. Materials and Methods: This study was a single-center retrospective observational study for patients who visited our COVID-19 aftercare outpatient clinic (CAC) established in Okayama University Hospital (Japan) during the period from 15 February 2021 to 15 July 2022. We classified the onset of COVID-19 in the patients into three groups, the preceding, Delta-dominant, and Omicron-dominant periods, based on the prevalent periods of the variants in our prefecture. Results: In a total of 353 patients, after excluding 8 patients, 110, 130, and 113 patients were classified into the preceding, Delta-dominant, and Omicron-dominant periods, respectively. Patients infected in the Omicron-dominant period had significantly fewer hospitalizations, milder illnesses, more vaccinations and earlier visit to the CAC than did patients infected in the Delta-dominant period. Patients infected in the Omicron-dominant period had significantly lower frequencies of dysosmia (12% vs. 45%, ** p < 0.01), dysgeusia (14% vs. 40%, ** p < 0.01) and hair loss (7% vs. 28%, ** p < 0.01) but had higher frequencies of fatigue (65% vs. 50%, * p < 0.05), insomnia (26% vs. 13%, * p < 0.05) and cough (20% vs. 7%, ** p < 0.01) than did patients infected in the Delta-dominant period. Conclusions: The transitional changes in long COVID symptoms caused by the two variants were characterized.

Clinical Characteristics of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Diagnosed in Patients with Long COVID

Background and Objectives: COVID-19 can be serious not only in the acute phase but also after the acute phase and some patients develop ME/CFS. There have been few studies on patients with long COVID in whom ME/CFS was diagnosed by physicians based on standardized criteria after examinations and exclusion diagnosis and not based on only subjective symptoms. The purpose of this study was to elucidate the detailed characteristics of ME/CFS in patients with long COVID. Materials and Methods: A retrospective descriptive study was performed for patients who visited a COVID-19 aftercare clinic established in Okayama University Hospital during the period was from February 2021 to April 2022. Results: Clinical data were obtained from medical records for 281 patients, and 279 patients who met the definition of long COVID were included. The overall prevalence rate of ME/CFS diagnosed by three sets of ME/CFS criteria (Fukuda, Canadian and IOM criteria) was 16.8% (48.9% in male and 51.1% in females). The most frequent symptoms in ME/CFS patients were general fatigue and post-exertional malaise (89.4% of the patients), headache (34.0%), insomnia (23.4%), dysosmia (21.3%) and dysgeusia (19.1%). Dizziness, chest pain, insomnia and headache were characteristic symptoms related to ME/CFS. The male to female ratio in ME/CFS patients was equal in the present study, although ME/CFS was generally more common in women in previous studies. Given that patients with ME/CFS had more severe conditions in the acute phase of COVID-19, the severity of the acute infectious state might be involved in the pathophysiology of ME/CFS. Conclusions: The prevalence rate of ME/CFS and the characteristic sequelae in the long COVID condition were revealed in this study.

Application of Kampo Medicines for Treatment of General Fatigue Due to Long COVID

Evidence regarding treatment for the acute phase of COVID-19 has been accumulating, but specific treatment for long COVID/post-COVID-19 condition has not yet been established. Treatment with herbal medicine might be one treatment option for long COVID, but there has been little research on the effectiveness of herbal medicine for long COVID. The aim of this study was to clarify the prescription patterns of Kampo medicines, which are herbal medicines that originated in China and were developed in Japan, for the treatment of general fatigue due to long COVID. A retrospective descriptive study was performed for patients who visited a COVID-19 aftercare clinic established in Okayama University Hospital during the period from Feb 2021 to Dec 2021 with a focus on symptoms accompanying general fatigue and prescriptions of Kampo medicine. Among the clinical data obtained from medical records of 195 patients, clinical data for 102 patients with general fatigue and accompanying symptoms were analyzed. The patients had various symptoms, and the most frequent symptoms accompanying general fatigue were dysosmia, dysgeusia, headache, insomnia, dyspnea, and hair loss. Prescriptions of Kampo medicine accounted for 24.1% of the total prescriptions (n = 609). The most frequently prescribed Kampo medicine was hochuekkito (71.6%) and other prescribed Kampo medicines were tokishakuyakusan, ryokeijutsukanto, juzentaihoto, hangekobokuto, kakkonto, ninjin’yoeito, goreisan, rikkunshito, and keishibukuryogan. Since the pathophysiology of general fatigue after an infectious disease is, in general, considered a qi deficiency in Kampo medicine, treatments with such compensation agents can be the major prescription as a complement for the qi. In conclusion, Kampo medicine can be one of the main pharmacological treatments for long COVID accompanying general fatigue.

Late-Onset Hypogonadism in a Male Patient with Long COVID Diagnosed by Exclusion of ME/CFS

After the acute phase of COVID-19, some patients have been reported to have persistent symptoms including general fatigue. We have established a COVID-19 aftercare clinic (CAC) to provide care for an increasing number of these patients. Here, we report the case of a 36-year-old man who developed post-COVID fatigue after acute infection with SARS-CoV-2. In the acute phase of COVID-19, the patient’s fever resolved within four days; however, general fatigue persisted for three months, and he visited our CAC 99 days after the initial infection. Examination revealed a high Aging Male’s Symptoms (AMS) score of 44 and low free testosterone (FT) level of 5.5 pg/mL, which meet the Japanese criteria of late-onset hypogonadism (LOH) syndrome. Imaging studies revealed an atrophic pituitary in addition to fatty liver and low bone mineral density. Anterior pituitary function tests showed a low follicle-stimulating hormonelevel and delayed reaction of luteinizing hormone (LH) after gonadotropin-releasing hormone (GnRH) stimulation, indicating the possibility of hypothalamic hypogonadism in addition to primary hypogonadism seen in patients with post-COVID-19 conditions. After the initiation of Japanese traditional medicine (Kampo medicine: hochuekkito followed by juzentaihoto), the patient’s symptoms as well as his AMS score and serum FT level were noticeably improved. Furthermore, follow-up tests of GnRH stimulation revealed improvements in LH responsiveness. Although many patients have been reported to meet the criteria of ME/CFS such as our case, we emphasize the possibility of other underlying pathologies including LOH syndrome. In conclusion, LOH syndrome should be considered a cause of general fatigue in patients with post-COVID-19 conditions and herbal treatment might be effective for long COVID symptoms due to LOH (264 words).

Detection of Male Hypogonadism in Patients with Post COVID-19 Condition

The pathogenesis and prognosis of post COVID-19 condition have remained unclear. We set up an outpatient clinic specializing in long COVID in February 2021 and we have been investigating post COVID-19 condition. Based on the results of our earlier study showing that “general fatigue” mimicking myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is the most common symptom in long COVID patients, a retrospective analysis was performed for 39 male patients in whom serum free testosterone (FT) levels were measured out of 61 male patients who visited our clinic. We analyzed the medical records of the patients’ backgrounds, symptoms and laboratory results. Among the 39 patients, 19 patients (48.7%) met the criteria for late-onset hypogonadism (LOH; FT < 8.5 pg/mL: LOH group) and 14 patients were under 50 years of age. A weak negative correlation was found between age and serum FT level (r = −0.301, p = 0.0624). Symptoms including general fatigue, anxiety, cough and hair loss were more frequent in the LOH group than in the non-LOH group (FT ≥ 8.5 pg/mL). Among various laboratory parameters, blood hemoglobin level was slightly, but significantly, lower in the LOH group. Serum level of FT was positively correlated with the levels of blood hemoglobin and serum total protein and albumin in the total population, whereas these interrelationships were blurred in the LOH group. Collectively, the results indicate that the incidence of LOH is relatively high in male patients, even young male patients, with post COVID-19 and that serum FT measurement is useful for revealing occult LOH status in patients with long COVID.