Examination of SARS-CoV-2 RNA in joint synovial fluid of patients with COVID-19 and acute knee arthritis

1. Introduction

With the rapid and exponential spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) throughout the world, the World Health Organisation declared a pandemic of a new respiratory disease known as coronavirus disease 2019 (COVID-19). The unstoppable COVID-19 pandemic is very important in terms of morbidity and mortality, and it seems that it will continue for a long time period [24, 31].

Coronaviruses have enveloped spike proteins, which bind to host cell surface receptors and then activate viral entry into target cells. The spike protein of SARS-CoV-2, binds to angiotensin-converting enzyme 2 (ACE2) receptor, and thus ACE2 has been identified as the viral receptor for SARS-CoV-2 infection [17]. In addition to the lungs, ACE2 is predominant in the gastrointestinal tract, kidney, and the heart [4, 14, 22, 23, 29]. Therefore, in COVID-19 patients, nucleic acids of SARS-CoV-2 can be detected not only in nasal and oral swabs but also in faeces, peritoneal fluid, and cerebral spinal fluid [5, 7, 15, 25, 28, 30]. As ACE2 expression has also been shown in the synovial tissues [4, 14, 22, 23], viral contamination of the synovial fluid has been hypothesized. However, it has not yet been fully established that there is COVID-19 involvement in the synovial fluid and to what extent, and therefore SARS-CoV-2 particles in joint fluid remains a topic of debate. In this context, the aim of this study was to evaluate the presence of SARS-CoV-2 in joint synovial fluid of patients with COVID-19.

2. Methods

3. Results

A total of 2476 patients were hospitalized and received treatment for a possible diagnosis of COVID-19 (radiologically positive or RT-PCR positive). While the RT-PCR test was positive in 318 patients (% 12.8), 2158 (% 87.2) were CT positive but RT-PCR negative. No patient had evident arthritis on admission but 12 patients (5 RT-PCR +, 7 CT +) (3.8%) developed acute arthritis during hospitalization. Twelve patients were consulted due to acute joint effusion. Of five patients with knee joint effusion and a positive RT-PCR test, the synovial tissue RT-PCR test was positive in only one patient. None of the patients with negative nasopharyngeal RT-PCR tests showed positive synovial fluid RT-PCR test (Fig. 1). There was no finding in favor of acute bacterial septic arthritis in the joint fluid in any patient as all cultures were negative (Table 1).

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Real-time RT-PCR of naso-pharyngeal swabs has been typically used to confirm the clinical diagnosis, and is the gold standard for the diagnosis of COVID-19 [2, 27]. Since SARS-CoV-2003 emerged, there has been convincing evidence that aerosol-generating procedures (AGP) could cause a potentially wider transmission radius of human-to-human coronavirus droplets [15, 21]. Most symptoms of patients with COVID-19 are related to the respiratory system. SARS-CoV-2 is mainly spread through respiratory droplets or close contact. There are few studies about the presence of the virus in body fluids [11, 18], and there have been no reports about the presence of the virus in synovial fluid.

Muscle and joint pain are common symptoms seen in many viral infections [1]. Viral arthritis is caused by several mechanisms induced by direct invasion and immune complex formation. Viral particles may act as antigenic components in immune complexes formed by the humoral response to viral infection. These immune complexes may be preferentially deposited in the joints, leading to arthralgia and arthritis [12]. In the current study, 12 patients with acute arthritis symptoms were tested for SARS-CoV-2 in synovial fluid with RT-PCR assay and only one sample was positive for the virus.

In a cadaver study conducted by Grassi at al [6] post-mortem synovial fluid samples were collected from the knees of five patients who died of COVID-19. SARS-CoV-2 RNA was not detected in any of the knee samples, despite the positivity of the throat swab. In another study, the case report by Hong et al. [9] showed reactive arthritis after COVID-19, but similarly, SARS-CoV-2 PCR was not performed on joint fluid. Contrary to this study, it was detected in synovial fluid in our study. In this context, our study is the first to be detected in synovial fluid.

The effect of coronavirus infection on joints is unknown. Viral arthritis has been reported to be able to recover with generalized symptomatic treatment [26]. However, some viral pathogens may have long-lasting clinical symptoms and require antiviral therapy [8, 26]. In a previous study, the presence of knee joint pain in COVID-19 positive patients was shown in only 2 patients [10]. However, these were based on clinical findings only, and to date, viral detection in synovial fluid has not been tested.

In many textbooks and publications, synovial fluid analysis is recommended as a routine procedure, which can significantly aid the diagnosis of arthritis [20]. In this context, the presence of SARS-CoV-2 was examined in synovial aspiration fluid in addition to cell analysis, as it was considered that demonstration of its presence, and evaluation of its relationship with clinical findings, would contribute to determining the duration of treatment.

The detection and analysis of nucleic acid in various biological samples of COVID-19 patients has been studied. Nasopharyngeal swab, sputum, blood, faeces anal swabs have been collected for SARS-CoV-2 nucleic acid detection [27]. The positive rate of SARS-CoV-2 nucleic acid test was highest in sputum at 48.68% (148/304 times), followed by nasopharyngeal swab at 38.13% (180/472 times), anal swab at 10.00% (12/120 times), faeces at 9.83% (24/244 times), and blood at 3.03% (4/132 times). It was also seen in that study that in some COVID-19 cases, the respiratory tract (nasopharyngeal swab/sputum) nucleic acid test result was negative but the gastrointestinal tract sample (fecal/anal swab) was positive [27]. Joob et al. [10] stated that in patients with arthralgia, COVID-19 might be easily missed. Therefore, it can be considered that the presence of the virus in joint fluid would be able to guide clinical diagnosis and treatment and could have a significant role in determining and eliminating the route of transmission, thereby preventing further spread of the epidemic.

Current recommendations on surgical consensus suggest caution when using laparoscopy for the theoretical possibility of viral transmission from tissue aerosolisation and peritoneal fluid during surgery [15]. In procedures involving electro-cauterisation, advanced coagulation and cutting devices, gas and vapor are produced by which peritoneal fluid is aerosolized and consequently the virus contained in the aerosol droplets. Healthcare personnel can potentially be infected by aerosolization of the virus, which can be provoked by all surgical procedures. Previous studies have demonstrated the presence of activated corynebacterium, human papillomavirus, hepatitis B virus, and human immunodeficiency virus in surgical vapors [13]

As there is continuing uncertainty about this issue in emergency/semi-emergency arthroscopic surgeries, it can be considered safer to try to reduce the use of cauterising devices such as radiofrequency in these surgeries and to perform the surgery with hypotensive anesthesia or bleeding reducing agents.

In many countries, semi-elective cases have started to become the norm. The extent of COVID-19 involvement in the synovial fluid has not been well established, and the presence or the absence of SARS-CoV-2 particles in the joint fluid and the possibility of contamination from a joint fluid remains a topic of debate. Thus, it can be considered that the presence/absence of the virus in the synovial fluid would contribute to guiding surgeons. However, the possibility of contamination from joint fluid remains uncertain.

Another issue related to the method of protection of healthcare professionals is that it is very important that the necessary precautions are taken due to the risk of transmission in arthroscopic surgeries. Although there have been studies related to the recommended personal protective equipment for orthopedic and trauma surgeons, these studies have focused on the uncertainty of transfer of other body fluids [7]. The risk of transmission through Aerosol - generating procedures (AGPs) as a result of the evaporation of blood and body fluid has been emphasized [7].

The available data in literature have not shown a direct relationship between viremia and clinical severity [6]. However, it is less likely that positive viremia will be detected when symptoms are mild or moderate than in critically ill patients [3]. If the same mechanism is hypothesised for other body fluids, it can be said that the greater the viremia, the greater the risk. There is no information currently avaailable about the virus passage to synovial fluids, but it can be suggested that potentially all patients, even those with mild to moderate SARS-CoV-2 respiratory symptoms could present viral load in synovial fluid, and this would result in increased exposure and risk of infection for the whole surgical team. In addition, clearance time may be different in body fluids. A previous study reported that the clearance time of SARS-CoV-2 in the digestive tract was later than that in the respiratory tract [27]. However, there is still uncertainty about joint fluid, as it may be seen in the knee joint later, as well as in the earlier period. In patients presenting with joint pain during the pandemic period, COVID-19 should be kept in mind and can be evaluated as an exclusion criterion.

This paper can be considered as a warning for the need to increase the level of awareness and protection for surgical teams, especially those involved in arthroscopic operations, as SARS-CoV-2 occurs in joint fluid and may be aerosolized to the environment.

5. Conclusion

This paper is the first to show the presence of SARS-CoV-2 in synovial fluid. This can be considered of importance for the determination and elimination of the route of transmission, thereby preventing further development and spread of the disease. This new result constitutes a significant warning for the safety of the operating team and demonstrates the need for an immediate update of the measures taken to protect surgical staff.

Funding

The authors report no funding.

Ethical approval

The study protocol was approved by the Local Ethics Committee of our university (Number: 907/2020) and Ministry of Health (Number: 104933/2020).