The risk of developing severe clinical forms of COVID-19 in healthcare workers in the initial period of the pandemic: non-occupational factors and laboratory prognostic indicators

Under the COVID-19 pandemic, healthcare workers were at the highest risk of getting infected with the disease; this necessitates specialized studies in this occupational group. The aim of the study was to identify non-occupational risk factors and laboratory markers indicating that severe clinical forms of new coronavirus infection would probably develop in healthcare workers in the initial period of the pandemic. The study included 366 workers who suffered COVID-19 in 2020-2021. The disease was confirmed by examining smears from the pharynx and nose with PCR. Some of the samples were examined using the SARS-CoV-2 whole genome sequencing technology. To determine laboratory prognostic indicators evidencing the development of more severe forms of the disease (pneumonia), a number of healthcare workers underwent laboratory examination during the acute period of the disease, namely: general clinical and biochemical blood tests, immunophenotyping of lymphocytes, analysis of the hemostasis system and cytokine levels. To study non-occupational risk factors of pneumonia, all healthcare workers after recovery were asked to fill in a Google form developed by the authors. The most severe clinical forms of COVID-19 were registered in healthcare workers who were older than 40 years, with low physical activity and a body mass index higher than 25.0, had diabetes mellitus and chronic diseases of the genitourinary system. When analyzing the results of laboratory tests, markers indicating development of pneumonia were identified and their critical values (cut-off points) were determined: the level of lymphocytes (below 1.955·109/l), T-cytotoxic lymphocytes (below 0.455·109/l), T-helpers (below 0.855·109/L), natural killers (below 0.205·109/l), platelets (below 239·109/L), erythrocyte sedimentation rate (above 11.5 mm/h), D-dimer (above 0.325 mcg/ml), total protein (below 71.55 g/L), lactate dehydrogenase (above 196 U/L), C-reactive protein (above 4.17 mg/l), and interleukin-6 (above 3.63 pg/l). The study identified non-occupational risk factors causing development of severe COVID-19 and established laboratory prognostic indicators.