Biochemical and Immune Indicators of COVID-19 Severity

Abstract

Background: Coronaviruses (CoVs) are a class of RNA viruses that infect humans and various
animals. They enter host cells via ACE2 receptors, which are widely distributed in organs
such as the heart, lungs, kidneys, and the digestive tract. COVID-19 infection causes systemic
illness, characterized by fever, cough, fatigue, sputum production, dyspnea, appetite loss, and
sometimes diarrhea. It can disrupt, damage, or even cause failure of multiple organs, particularly the lungs, kidneys, and sites of prior injury. Immune activation is marked by heightened
T-lymphocyte and macrophage responses, producing elevated levels of cytokines, notably
interleukins such as IL-2, IL-4, and IL-6, which play complex and sometimes antagonistic roles
in immune regulation.
Objective: To investigate alternative laboratory markers for the diagnosis and prognosis of
COVID-19, particularly in settings where RT-PCR testing is unavailable, focusing on the role of
inflammatory markers and biochemical parameters.
Methods: During periods when RT-PCR testing was inaccessible because of logistical constraints, conventional laboratory tests were utilized to establish diagnostic and prognostic criteria for COVID-19. These included measurement of serum ferritin, interleukin-6 (IL-6), lactate
dehydrogenase (LDH), and hematological parameters such as hemoglobin levels to assess anemia and iron status.
Results: Patients with COVID-19 frequently exhibited rapid elevation of ferritin levels, which
correlated with increased IL-6 concentrations. Hyperferritinemia was associated with anemia
and excessive iron loss. LDH levels were also elevated and served as an independent predictor
of mortality, regardless of underlying conditions.
Conclusion: In the absence of RT-PCR testing, routine laboratory markers—including ferritin,
IL-6, LDH, and hematological profiles—can serve as valuable tools for the diagnosis and prognostic assessment of COVID-19. Elevated ferritin and LDH levels, in particular, are linked to
increased disease severity and higher mortality risk.