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Investigating Whether the Severity of SARS-CoV-2 Infection Is Higher in Liver Transplant Recipients: A Single-Center Experience


Objectives: Liver transplant recipients have been reported to be a high-risk population for severe disease from COVID-19 infection. In this cross-sectional, single-center study, we investigated whether liver transplant increased the risk of death and severe disease in patients with SARS-CoV-2 infection.
Materials and Methods: We collected data and serum anti-SARS-CoV-2 immunoglobulin M and im-munoglobulin G results of 91 liver transplant recipients seen from September 2020 to March 2021. Liver transplant recipients were enrolled during presentation for scheduled routine follow-up visits. All patients who required serum anti-SARS-CoV-2 immunoglobulin M and immunoglobulin G tests completed a ques-tionnaire on clinical symptoms during the previous 6 months.
Results: Among the 91 patients with SARS-CoV-2 immunoglobulin M and G results, 7 patients had a known history of symptomatic COVID-19 during the previous 6 months. Of the 84 participants who completed the questionnaire, 21 (25%) had positive anti-SARS-CoV-2 immunoglobulin M and G results. These 21 patients also received COVID-19 polymerase chain reaction tests, which were negative in all 21 patients. Overall, only 7 patients stated that they experienced flu-like upper respiratory tract infection symptoms or diarrhea.
Conclusions: We documented past SARS-CoV-2 infection in only 25% of our outpatient liver transplant recipients, and most were asymptomatic. We found no significant relationship between symptoms and seropositivity for SARS-CoV-2.

Key words : COVID-19, Pandemic, Serum anti-SARS-CoV-2 immunoglobulin M and immunoglobulin G


Coronavirus disease 2019 (COVID-19), caused by a novel coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is presently the most common global disease. Groups at high risk for this disease, which has been declared a pandemic by the World Health Organization, are still not fully determined. Immunosuppressed patients are regard-ed as a high-risk cohort. In this regard, previous experiences with similar viruses, such as SARS-CoV and MERS-CoV, have suggested that solid-organ transplant recipients are prone to increased morbidity and mortality. Early published studies in liver transplant (LT) and solid-organ transplant recipients with COVID-19 have reported a rate of severe infection of up to 20%, exceeding the rate of the general population.1,2

Initial symptoms of patients with COVID-19 can vary, with about 80% of patients having symptoms of mild illness.3 Patients with SARS-CoV-2 may be completely asymptomatic or progress with severe disease. Comorbidities and advanced age are the most important risk factors among LT recipients and the general population.1 It is estimated that COVID-19 will be more symptomatic and severe in LT recipients due to immunosuppression treatments. In this study, we aimed to determine the frequency of asymptomatic or mild disease in LT recipients seen at our center.

Materials and Methods

Study patients were enrolled from LT recipients who came for routine control visits between September 2020 and March 2021 to the Ankara City Hospital Liver Transplant outpatient clinic (Ankara, Turkey). All patients were older than 18 years of age and had previously undergone LT. Liver transplants had been performed using both deceased donors and living donors. Living donor LT procedures were with first- and second-degree relatives of the respective recipients. The ethics committee of Ankara Bilkent City Hospital approved the study (approval number: E2-21-280). The study was conducted in accordance with good clinical practice principles and the Declaration of Helsinki.

Study enrollment was performed when patients presented for scheduled routine follow-up visits. Included patients were those who underwent serum COVID-19 immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody tests. Patients received SARS-CoV-2 polymerase chain reaction (PCR) tests with a nasopharyngeal-oropharyngeal swab within 3 days of when they showed a positive antibody test. All patients completed a questionnaire that queried them on their common clinical symptoms (fever, cough, diarrhea, myalgia, nausea, and vomiting) during the previous 6 months. All included patients were also questioned on history of contact with any COVID-19-positive individual and hospitalization.

We evaluated the performance of COVID-19 serology testing on chemiluminescent immunoassay per the manufacturer’s protocol (ADVIA Centaur) and with SARS-CoV-2 Total (COV2T; Siemens Healthcare Diagnostics). These serological tests use the SARS-CoV-2 Spike protein (S protein) as a viral labeling protein to detect anti-SARS-CoV-2 antibodies. Test results were interpreted as positive if the signal value of the Siemens test (index) was ≥1.0 of total antibodies. All serum anti-SARS-CoV-2 total results of all patients were collected before vaccination for COVID-19.

Statistical analyses
Statistical analyses were performed with IBM SPSS Statistics for Windows version 26.0 software. Continuous variables are expressed as medians and ranges. Categorical variables are expressed as counts and percentages. Between-group comparisons were performed using the Mann-Whitney U test for continuous variables and the chi-square test (or Fisher exact test where appropriate) for categorical variables. For P results, the use of the chi-square test or the nonparametric t test is provided. P < .05 indicated statistical significance.


We conducted a retrospective study of 91 LT recipients at an LT center in Ankara City Hospital, with sample collection taking place between September 2020 and March 2021. Serum anti-SARS-CoV-2 IgM + IgG results were positive in 28 of 91 patients. Seven of these 28 patients were not included in the analysis because they had a known history of COVID-19. Three of the 7 patients (42.9%) had self-limited disease, with none requiring hospitalization or supplemental oxygen treatment for COVID-19. However, there were 3 patients among the 7 (42.9%) who needed hospitalization, and 1 patient (14.3%) who was already in the hospital when he was diagnosed with COVID-19. Twenty-one patients (21/28, 75.0%) had no history of SARS-COV-2 infection and no specific symptoms. We tested all patients with positive serum antibodies with a nasal-oropharyngeal swab PCR test, and the results were negative.

There were 84 patients (7 of the 91 were excluded because of COVID-19 history) with median age of 52.1 years (interquartile range, 21-68 y) comprising 60 men (71.4%) men and 24 women (28.5%) who completed the questionnaire. Hypertension was the most common comorbid disease (15/84, 17.9%), followed by type 2 diabetes mellitus (10/84, 11.9%) (Table 1). All 84 participants were contacted and retrospectively surveyed for clinical symptoms of COVID-19 in the prior 6 months (Table 2). There were no significant differences between patient symptoms with positive test results (serum IgG + IgM) and symptoms described in those with negative test results.

Of the 91 patients, 28 were serum antibody positive (7 of the 28 patients had been diagnosed with COVID-19 symptoms before the study). Another 7 of the 28 patients had at least 1 symptom, but they had no COVID-19 diagnosis history. The remaining 14 patients of 28 were completely asymptomatic, but their serum antibody levels were positive. The 21 seropositive patients for SARS-CoV-2 were compared with the 63 seronegative patients in terms of symptoms over the previous 6 months. We observed no association between results of questionnaire inquiries and COVID-19 seropositivity (Table 3).

We also examined patient characteristics between the seronegative and seropositive groups. Mean age of the seropositive group was 51.5 ± 9.8 years, and the mean age of the seronegative group was 52.3 ± 11.5 years (P = .378). There were also no significant differences between the 2 groups in terms of sex, body mass index, and aspartate aminot-ransferase (AST) and alanine aminotransferase (ALT) levels (Table 2).

Among 11 LT recipients who stated history of contact with individuals diagnosed with COVID-19, 4 LT recipients (36.4%) had COVID-19 antibody positivity. Among 20 patients with a history of hospitalization, 6 patients (30.0%) showed serum SARS-CoV-2 IgM + IgG antibody positivity. There was no significant difference between hospitalization and serum antibody positivity (P = .554).


In this study, we evaluated LT transplant recipients who were followed in our LT outpatient clinic in terms of serum SARS-CoV-2 IgM + IgG levels and history of COVID-19 disease. The serum antibody positivity rate was 30.8% (28 of 91 patients) in LT recipients included in our study. The seroprevalence rates for the region where we conducted our current study are unknown. However, seropositivity was found to be 12.3% (115/932) in a seroprevalence study conducted on health care professionals in Turkey. The seropositivity among previously undiagnosed health care workers was calculated as 2.7%.4

Limited data are available for asymptomatic or subclinical infections in the transmission of the SARS-CoV-2 virus.5 Among the 91 LT recipients seen in our clinic during the study period, 7 patients (7.7%) had an asymptomatic history of COVID-19. Among 28 antibody-positive patients, 21 (75%) were not diagnosed with COVID-19, with questionnaire results stating that they had no specific COVID-19 symptoms. Among the 91 total LT recipients seen in our clinic during the study period, 23.1% (21/91) had subclinical or asymptomatic seropositivity.

In a previous study, acute and past SARS-COV-2 infections were documented in 3.7% of LT recipients. In the same study, the asymptomatic seropositivity rate was reported as 62.5% (5/8).6 The rate of asymptomatic COVID-19 in LT recipients was reported as 6% in a Spanish series and as 14% in a multinational study (n = 151).7,8

There were no differences between serum AST and ALT levels in the groups who were seropositive versus seronegative; however, the serum AST and ALT values in the possible disease processes were unknown. Studies have shown a relationship between severe disease and elevated liver enzyme levels in patients with COVID-19. In infected individuals with SARS-CoV-2, increased serum liver enzyme levels were shown in approximately 15% of patients.9 In our experiences with transplant patients with COVID-19 at our center, we found serum AST or ALT levels to be 2 times or higher in 23.5% of patients diagnosed with symptomatic COVID-19 (n = 4/17). Increased liver enzymes are usually reversible. As expected, seropositivity was not associated with increased liver enzymes.

Asymptomatic or subclinical COVID-19 partici-pants with seropositivity include those with history of contact with people diagnosed with COVID-19 and those with history of hospitalization. In contrast to the expected, seropositivity was not associated with history of contact or hospitalization.

A limitation of our study was that patients were evaluated over a period of 6 months to determine seroprevalence from serum antibody tests conducted during routine follow-up.


There has been an increase in studies related to the course of COVID-19 in LT recipients. However, the frequency of asymptomatic or subclinical disease is not yet clear. Although the number of patients in our study was low, the seropositivity rate (30.8%) and the rate of asymptomatic patients (75.0%) among all included LT recipients were higher than expected. We need large-scale seroprevalence studies to reach more reliable data.


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DOI : 10.6002/ect.2021.0494

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From the 1Department of Gastroenterology, the 2Department of Infectious Disease and Clinical Microbiology, and the 3Department of Gastrointestinal Surgery, Ankara City Hospital, Ankara, Turkey
Acknowledgements: The authors have not received any funding or grants in support of the presented research or for the preparation of this work and have no declarations of potential conflicts of interest. Data that support the findings of this study are available from the corresponding author upon reasonable request. We would like to thank our precious nurses İpek Ünlü and Cazibe Kılınç for their devoted work during the follow-up of the patients in the liver transplant outpatient clinic.
Corresponding author: Derya Arı, Department of Gastroenterology, Ankara City Hospital, 06100, Çankaya, Ankara, Turkey
Phone: +90 505 567 1527