Features of clinical blood biochemistry in patients who have suffered a new coronavirus infection

The COVID-19 pandemic, which began in December 2019, was caused by the new coronavirus SARS-CoV-2. SARS-CoV-2 is a shell virus containing a single positive chain genome and using angiotensin converting enzyme 2 (ACE2) as a cell entry receptor. The targeting of SARS-CoV-2 on several tissues expressing ACE2 explains the multifactorial pattern of symptoms: fever, dry cough, myalgia, fatigue and shortness of breath. These symptoms do not always stop after COVID-19, and symptoms may reappear within 12 weeks, which indicates the development of post-COVID syndrome (long COVID). Due to the extensive symptoms and comorbidity of patients, the clinical diagnosis of post-COVID syndrome is difficult. The aim of the study is to identify pathognomonic indices of biochemical blood analysis in convalescents, indicating the development of post-COVID syndrome. Patients and study design: a retrospective observational one-moment study of 373 case histories and outpatient records was conducted for the patients exposed to COVID-19 not later than 12 weeks ago. The initial course of the disease (disease) was assessed using the WHO Clinical Progression Scale. The severity of post-COVID syndrome (clinical outcomes) was assessed on the functional status scale after COVID-19 (PCFS). All subjects are divided into four groups, the names of which reflect the severity of COVID-19 and the severity of the post-ovoid condition: 1st group, “mild COVID-19 / 0-2 PCFS class”; 2nd group, “mild COVID-19 / 3-4 PCFS class”; 3rd group, “medium and severe COVID-19 / 0-2 PCFS class”; 4th group, “medium and severe COVID-19 / 3-4 PCFS class”. The sample was described by calculating the median (Me) values and interquartile range expressed as Q1 and Q3 (Q0.25-Q0.75). The reliability of the differences between independent samples was assessed with nonparametric Mann–Whitney U-test and the Student’s t-test. Upon evaluation of clinical blood biochemistry, the alanine aminotransferase (ALT) level in group 1 was higher than in groups 2 and 4, the aspartate aminotrasferase (AST) level in group 2 was higher than in groups 1 and 3. The indexes of total cholesterol and LDL did not show statistically significant differences between the groups. Creatinine levels in group 3 are higher than in group 1, being lower in group 4 than in other groups. Significant differences were observed upon qualitative assessment of C-reactive protein (CRP). There were 2-3 times more subjects with elevated CRP levels in groups 2 and 4 than in group 1. A minimal biochemical profile, including an assessment of the level of transaminases and creatinine, a qualitative or quantitative assessment of C-reactive protein, may indicate development of chronic inflammation. Patients of this group need to undergo an additional examination, e.g., general urine analysis and determination of albumin level in urine, dynamic GFR calculation, in order to prevent the development of persistent renal impairment.