The coronavirus disease-2019 (COVID-19)is a pandemic disease caused by SARS -COV-2 which belongs to the β-coronavirus family . The majority of affected individuals exhibit no or mild to moderate symptoms, but up to 15% of patients develop severe pneumonia with approximately 6% progressing to acute respiratory distress syndrome and multiorgan failure.

Biomarkers are needed to identify patients will suffer rapid disease progression to severe complications and death. Preliminary studies describe vasculitic processes underlying organ damage in seriously ill patients, induced by the activation of inflammatory cascades, complement activation and pro-inflammatory cytokines (i.e. interleukin).

The severity of Vasculitic damage is unfortunately not easily predictable through currently used laboratory biomarkers such as D-dimer or prothrombin time/activated partial thromboplastin time.

The severity of the disease is mainly driven by diffuse interstitial lung diseases. YKL-40 has a pro mitogenic action on pulmonary fibroblasts, increases the activity of macrophages and is associated with inflammatory disorders. In ILD, YKL-40 has been described to be associated with the severity of lung diseases and with the risk of death.

YKL-40 serum levels could therefore be of interest for diagnosis and prognosis since it is at the cross-link between vascular and epithelial lung damage.

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Inclusion Criteria:

• • Group one should be diagnosed by RT-PCR (reverse transcriptase polymerase chain reaction).

  • Healthy individual must be without a prior history of chronic inflammation in the lung.

Exclusion Criteria:

• Patients with acute renal failure (ARF) or multiple organ damage (MOF).

All patients come to Assiut university with clinical manifestation of COVID -19