This letter to the Editor discusses laboratory abnormalities in patients with COVID-19 infection. The authors highlight the importance of laboratory tests in the early detection, diagnosis, and management of COVID-19. They emphasize that laboratory diagnostics play a crucial role beyond etiological diagnosis and epidemiological surveillance, as they are used to assess disease severity, define prognosis, follow-up patients, guide treatment, and monitor therapeutic outcomes. A systematic review of 11 studies identified common laboratory abnormalities in patients with COVID-19, including lymphopenia (35–75%), increased CRP (75–93%), LDH (27–92%), ESR (up to 85%), and D-dimer (36–43%), as well as low serum albumin (50–98%) and hemoglobin (41–50%). These abnormalities were associated with adverse clinical outcomes. Procalcitonin and coagulation tests were particularly significant, with procalcitonin levels increasing as the prognosis worsened. Coagulation parameters were more frequently deranged in patients who died from COVID-19, indicating the critical role of these tests in monitoring patients. The authors note that while some limitations exist in the current literature, the available data suggests that many laboratory parameters are abnormal in patients with COVID-19, and some may serve as significant predictors of adverse outcomes. They conclude that laboratory testing should be considered a routine part of monitoring patients with COVID-19.This letter to the Editor discusses laboratory abnormalities in patients with COVID-19 infection. The authors highlight the importance of laboratory tests in the early detection, diagnosis, and management of COVID-19. They emphasize that laboratory diagnostics play a crucial role beyond etiological diagnosis and epidemiological surveillance, as they are used to assess disease severity, define prognosis, follow-up patients, guide treatment, and monitor therapeutic outcomes. A systematic review of 11 studies identified common laboratory abnormalities in patients with COVID-19, including lymphopenia (35–75%), increased CRP (75–93%), LDH (27–92%), ESR (up to 85%), and D-dimer (36–43%), as well as low serum albumin (50–98%) and hemoglobin (41–50%). These abnormalities were associated with adverse clinical outcomes. Procalcitonin and coagulation tests were particularly significant, with procalcitonin levels increasing as the prognosis worsened. Coagulation parameters were more frequently deranged in patients who died from COVID-19, indicating the critical role of these tests in monitoring patients. The authors note that while some limitations exist in the current literature, the available data suggests that many laboratory parameters are abnormal in patients with COVID-19, and some may serve as significant predictors of adverse outcomes. They conclude that laboratory testing should be considered a routine part of monitoring patients with COVID-19.