key: cord-0995225-txraq6kh authors: Duś-Ilnicka, Irena; Szczygielska, Anna; Kuźniarski, Amadeusz; Szymczak, Aleksander; Pawlik-Sobecka, Lilla; Radwan-Oczko, Małgorzata title: SARS-CoV-2 IgG Among Dental Workers During the COVID-19 Pandemic date: 2022-02-10 journal: Int Dent J DOI: 10.1016/j.identj.2022.02.003 sha: 05b06059cb42c2b8c4e3559af41e2beaf58740aa doc_id: 995225 cord_uid: txraq6kh OBJECTIVES: Since the SARS-CoV-2 outbreak in 2019, special safety protocols were introduced in dentistry. Dental professions were established mostly at risk of gaining the virus because of aerosol generating procedures used. This preliminary study, starts the cycle of the laboratory protocols describing the quality and efficacy of laboratory tests in the SARS-CoV-2 IgG detection in the serum of asymptomatic dental personnel during the last quarter of 2020. METHODS: IgG levels were measured with the use of semi-quantitative enzyme-linked immunosorbent assay (ELISA) in vitro diagnostic (IVD) kit in the serum of study group that consisted of 127 employees of the dental clinic, divided into three subgroups: SUB1: dentists (n=67), SUB2: dental assistants, dental hygienists, nurses, laboratory workers (n=40), SUB3: administrative workers (n=20). Pearson analysis of results from the questionnaires attached to the study protocol were provided, to assure the results compare to the subjects impressions about their general health. RESULTS: Positive ELISA IgG results were received in 6% (4 subjects) of the SUB1 group, 7.50% (3 subjects) from the SUB2 group, and 5% from the SUB3 group. Percentage of subjects without work interruption from the beginning of pandemics involved 54% of dentists and 60% of chairside assistants. CONCLUSION: Serum IgG prevalence with the use of semi-quantitative test was low, and further research on the biobanked samples has to be followed, to conclude the levels of IgG with quantitative methods and/or to evaluate the presence of neutralizing antibodies in dental personnel. Since the low representation of seropositivity studies in this group, it will be crucial to confirm the risk of COVID-19 transmission in dental offices. Dentistry is a medical profession that has been strongly associated with a major risk of infection during the COVID-19 pandemic (1, 2) , since it was established that the SARS-CoV-2 virus is transferred by salivary droplets and by bioaerosols generated from the respiratory tract (3, 4) . Because of its availability, saliva represents a non-invasive specimen for COVID-19 research (5, 6) , and the SARS-CoV-2 viral load in this biomaterial has been confirmed in various studies (7, 8) . Special precautions in dental studies during the pandemic period were based on the risk of operating in the open oral cavity with the use of aerosol-generating procedures (AGPs) (1, (9) (10) (11) . Common AGPs in the dental office involve the use of such equipment as high-speed air turbines (12, 13) . To avoid the potential spread of SARS-CoV-2 during dental AGPs, a high level of personal protective equipment (PPE) is required (3) . At the beginning of the pandemic, when the necessary PPE was scarce due to delays in shipment in the East Asia, Europe and the United States (US), anxiety about getting infected was common among medical workers, like in the study presented in Israel (14) (15) (16) . Similar fears prompted many dental surgeries around the world to close during the first wave of the pandemic (2, 17, 18) . As the pandemic progressed many scientific groups reported that the scale of the SARS-CoV-2 infection among the medical doctors vary between countries. As presented by Iyengar et al. dentists were the medical group that was suggested to be more prone to acquire COVID-19 in India (2 reported COVID-19 related deaths till the end of 2020, percentage not provided) (19) . Researchers from Turin (Italy) evaluated the seroprevalence of COVID-19 antibodies among the medical workers, however only in the group of medical doctors without including dentists. This research however described the group of the clinicians that are in direct contact with patients as those that might create antibodies for SARS CoV-2 with the higher probability (7.5% of the whole study group) (20) . Also the study from Germany showed that dentists were getting infected by the virus in the scale of 0.2% from the whole group of medical sector (21) . Additional problems arise if dental patients are treated in open-plan clinical environments such as those in teaching hospitals with multiple patients in dental chairs and operators in close proximity (12, 22) . For this reason, protocols created at the beginning of the pandemic assumed that only urgent procedures such as those involving pain reported by the patient, or the risk of loss of a tooth, should be performed, but other dental procedures should be postponed (23) (24) (25) . However, with the advance of the pandemic, dental work became impossible to avoid, despite the dentists' apprehension about being infected with SARS-CoV-2 (25, 26) . Testing for SARS-CoV-2-specific IgG proteins is not a laboratory procedure for the diagnosis of infection with the virus, but rather a measuring tool for the immunological response to a previous infection or contact with the virus (27) . WHO provides for the optional diagnostics of antibody detection with semi-quantitative serological assays as being suitable for diagnosis of SARS-CoV-2 antibodies, and this measuring tool was used in this research (27) . The Academic Dental Polyclinic attached to the Wroclaw Medical University (Wrocław, Lower Silesia region, Poland) provides a dental treatment for patients in the fields of conservative dentistry, oral surgery, periodontology, prosthodontics and oral mucosal diseases, and is also a teaching unit for around 450 dental students each year. It has been open to patients during the pandemic and performed all necessary procedures in the field of dentistry. The aim of this study was to perform a screening test for SARS-CoV-2 IgG antibodies with the semi-quantitative ELISA IVD technique among the dental workers of the Academic Dental Polyclinic, which provides a workplace for 180 dentists. The study protocol in written form was approved by the appropriate Wroclaw Medical University Bioethics Committee before the research started (Decision no. 576/2020). Each of the participants signed an informed consent to participate in the study, and was able to ask questions regarding the survey, as required by Declaration of Helsinki. Specimens were collected from healthy volunteers at the Academic Dental Polyclinic attached to the Wroclaw Medical University (Wrocław, Lower Silesia region, Poland). Healthy volunteers were considered the individuals who were not suffering of any significant illness relevant to the proposed study, for this reason it has been considerednot undergoing any pulmonary infections by probable COVID-19 background. Volunteers were within the ordinary range of body measurements, not hospitalized, attending the common working space at the Academic Polyclinic. Total number of 127 medical personnel workers from the clinic were included. Volunteers were divided into three subgroups: 1. SUB1: dentists 2. SUB2: dental assistants, dental hygienists, nurses, laboratory workers 3. SUB3: administrative workers. The reason for this kind of the subgroup division was the time exposed to direct aerosol contamination (dentist the most, administrative workers the least). The inclusion criteria for the study group were working clinically during the COVID-19 pandemic, and for the administrative workers, working in direct collaboration with dentists and dental workers among the regional dental clinic's facilities. Exclusion criteria were symptoms of respiratory disease such as cough, fever or dyspnoea, or being under quarantine. Patients were asked to fill in the necessary documents and short questionnaire about the presence of flu-like symptoms, influenza vaccination, number of household members, and days off from professional work in the period from the beginning of the pandemic (15 March) to 28 September 2020. Concerning the subgroups working hours in the clinic during the pandemic, professionals from SUB1 group were working minimum of 240 hours with patients during the students clinical classes in the period of 10 months (from October to June). SUB2 and SUB 3 consisted mostly in full-time professionals working 40 hours per week. Most of the doctors in dentistry (SUB1) were working in more than one clinic during some period of the pandemic. All of the clinical groups working in the dental clinic facility who have direct contact with patients have been allocated a higher level of PPE as listed in Section 2.4. Triage procedures for patients attending the clinic have been implemented, and phone-only registration has been provided. In the case of suspected respiratory tract disease mimicking symptoms of COVID-19, patients were asked to postpone their dental appointment for 14 days. Enrolled patients have their temperature measured on entrance and are asked to sanitise their hands and fill out the COVID-19 information sheet. Waiting rooms have been adapted with measured social distancing markers and cleared of flyers, and patients are asked to attend exactly at the time of their visit. In contrast to some dental hospitals that work with the dental chairs in an open plan (22), the regional dental clinic consists of all closed and separate operating rooms. Additional UV flow lamps were purchased. Gravitational ventilation has been provided, and the equipment is disinfected after each patient. Blood collection was carried out at three different time intervals during the third quarter of 2020: 28 ). An hour after the collection, the blood samples were centrifuged at 2,500 rpm for 20 minutes at room temperature, and the serum was kept at 4°C until the analysis on the same day, or at -20°C if the laboratory procedures were delayed. The level of IgG in blood serum was determined using an IVD-certified ELISA kit for Statistical analysis was carried out using three libraries: Python (version 3.9.2), Scipy The total number of subjects involved in the study was 127, and 7 ( The group consistency is presented in Table 1 . Dividing the IgG results into subgroups, 6% (4) dentists tested positive for SARS-CoV-2 IgG, along with 7.5% (3) from group SUB 2 (chairside personnel), and 5% (1) from subgroup SUB 3 (administrative workers). Collectively, 8 subjects in the whole investigated group gave positive results for IgG SARS-CoV-2 ( Table 1 ). The highest number of positive ELISA IgG results was observed on Day 3 of blood collection (19.11 .2020). The number of declared symptoms in all subgroups was also higher on this day (Figure 1, Of the 8 cases with positive PCR results for SARS-CoV-2 infection, positive ELISA for IgG antibodies were only obtained in 4 cases. Although IgG antibody was present in the next 4 cases, the PCR test for SARS-CoV-2 was negative. There were no significant statistical differences between the subgroups when the number cohabiting in the household was taken into consideration in the light of a positive IgG ELISA value. Statistical analysis was performed using a Chi-square test for independence of variables in a contingency table with p=0.2047, statistic value = 8.6 and degrees of freedom = 6, see Table 2 . In the questionnaire about declared flu-like symptoms, prevalence across the job groups was highest for dentists (Figure 1, subfigure B) . Among the positive results for SARS-CoV-2 IgG antibodies obtained with the use of the ELISA technique were taste disorders, high temperature (over 38.0℃) and feeling of weakness (Figure 1 subfigure C) . In addition to the above, Pearson correlation statistics for entire group of subjects were evaluated. The correlations for whole group of subjects worth noting were those with low p value and high R coefficient. An R2 coefficient above 0.5 was interpreted as a strong correlation, increasing towards 1.0. The value of p was used to determine the validity with which the above correlation can be interpreted as correct. Between positive RT-PCR and positive ELISA results, the observed coefficient was 0.505 with p<0.0001. Statistical descriptions of the values of the parameters determined during the research of the subgroups of dentists (SUB1) and chairside assistants (SUB2) based on the questionnaire were developed in the form of a heatmap (Figure 2) . The correlation is presented by the use of colour: the darker the colour, the stronger the Pearson correlation, and the higher the R index. In this study, dentists from all specialities (dental surgeons, periodontologists, orthodontists, conservative/restorative dentists, and prosthetic dental specialists) were included. We did not observe any variation in the results of SARS-CoV-2 among the dental specialisations. Similarly, there were no significant differences between the investigated subgroups of dentists, dental assistants, nurses, laboratory workers, and administrative workers who share common spaces and professional interests as well as sharing the same workspace (building). That is in concordance with Sarapultseva et al, that did not observe the differences in the IgG presence among chairside assistants and dentists (29) . In our study, the prevalence of flu-like or COVID-19 symptoms was highest in the group was that researchers were not responsible for the molecular SARS-CoV-2 tests, and for such it was not possible to gain the information about the date and type of the test done by Healthy Volunteers participating in our research. In these last 4 cases, the subjects could have had asymptomatic infection, so they did not have the basics requirements for a PCR test. These cases of infection without obvious symptoms could possibly have involved many people, and without the assessment of IgG production, it is not possible to know more about this situation in the whole population (30) . In our study also the administrative workers were involved. Even if this group has no direct contact with the patients, the study presented subjects from all subgroups sharing the same workspace. Also among this group were support staff (cleaning personnel who are involved in cleaning of the dental surgeries and corridors). The results for IgG SARS-CoV-2 antibodies in this subgroup were relatively low (4.4%). There is a similar study that provided results of the seroprevalence among dental workers in United Kingdom, where also subject not involved in the direct work have been included (18) . However, unlike in our study, the aim of researchers was to provide the information about the seroprevalence among the group in time, also after the vaccination against COVID-19. Jackson et al. reported 78% agreement with the statement that dental procedures generate aerosol (3) . However, it is important to underline that in the cited article, the authors did not divide dental procedures into subgroups according to the risk of generating bioaerosols, while their diversity generates a need for safety classification (10) . All the dental procedures were analysed as an uniform group, which might be a reason for the result discussed in their study (3) . In the research conducted by Abdelkarim et al., the contaminated surface area using a high-speed air turbine reached 77.3%, but use of dental lasers caused only 3.8% to 7.3% of surfaces to be contaminated (13) . The proportion of surfaces contaminated is shown to be strictly related to the dental technique used, and for this reason, in periodontology manual scaling and polishing was recommended instead of ultrasonic techniques (24) , but some of the contamination might have been caused even from the removal of impacted third molars or routine extractions (11) . At the beginning of the risk assessment, the limitations of activities in dental offices were introduced (23) . The range of dental services provided in the office as part of general primary care, dental surgery, paediatric dentistry and conservative dentistry was limited to procedures necessary in cases of urgent need for intervention: i.e. pain, inflammation and purulent processes, injuries, cysts, and conditions with risk of complications in patients (32, 33) . Limitations of the study includes, that the research was not covering all the dental workers from the Academic Dental Polyclinic. This issue has however been resolved by scheduling in the parallel longitudinal research. Additionally, semi-quantitative enzymelinked immunosorbent assay might create discrepancies between the results and the actual concentration of the antibodies. To our knowledge, this one of the few available reports providing blood IgG results of all the co-working professionals in dental area such as dentists, chairside assistants, and administrative groups working together within one dental clinic. This research is in accordance with the latest statements that the risk of COVID-19 transmission in dental offices, even during aerosol-generating procedures and in the prevalence of asymptomatic patients, is low if the safety measures and use of PPE are followed. Tables: Table 1 . Study group consistence in division to three subgroups (SUB 1 = dentists, SUB2 = chairside assistants, SUB3 = administrative workers) Table 2 . Numbers of dental workers receiving positive and negative results in accordance to the number of people in the household. The larger the value, the closer the color is to brown, indicating a stronger correlation. And the lower the value, the color is closer to yellow, which means a lower correlation. (C and D) Colors correspond to Pearson correlation values. The higher the value, the higher the correlation between the two factors and the color more similar to brown. The smaller the value, the lighter the color closer to yellow. 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