This study aims to provide some insight into the variation of SD-D protein levels in patients with Covid-19 (-) pneumonia, Covid-19 (+) pneumonia, and CT negative Covid-19 infection in comparison to the normal population through a larger number of cases. Objective of the study is to determine the serum surfactant protein D (SP-D) levels in Covid-19 pneumonia infection.

This study aims to provide some insight into the variation of SD-D protein levels in patients with Covid-19 (-) pneumonia, Covid-19 (+) pneumonia, and CT negative Covid-19 infection in comparison to the normal population through a larger number of cases. Subjects will assessed in accordance with the inclusion and exclusion criteria, they were divided into four groups as the CT (-), PCR (+) SARS-CoV-2 infection group, SARS-CoV-2 (+) Pneumonia Group, CT (+), PCR (-) Suspected Pneumonia Group and Healthy group (Control Group). Demographic data, medical history, vital findings (fever, blood pressure, sPO2), laboratory findings (complete blood count; C-reactive protein (CRP), D-dimer, Ferritin and hsTnT parameters) and radiological findings, time to onset of symptoms, Comorbid diseases, hospitalization location of the patients (service or ICU), clinical scores, CT severity scores will determine. SP-D level will analyze by the Enzyme-Linked Immunosorbent Assay (ELISA) method.

For patients;

Inclusion Criteria:

• who presented to the Covid-19 outpatient polyclinic of the ED with pneumonia symptoms,
• whose CT imaging's were compatible with Covid-19 pneumonia in accordance with the RSNAEC criteria and whose PCR tests were positive,
• whose SARS-CoV-2 PCR tests were positive as a result of contact tracing,
• who presented to the ED for further examination.
• who gave their written consent to participate in the study.
• Giving written consent to participate in the study.

Exclusion Criteria:

• diagnosis of kidney or liver failure
• acute pulmonary embolism
• chronic inflammatory disease history (rheumatological disease, autoimmune disease),
• pregnancy
• presence of any cancer diagnosis
• chronic obstructive pulmonary disease
• asthma disease,
• history of cerebrovascular disease.
• the patients whose CT imagings were compatible with Covid-19 pneumonia but whose PCR tests were negative were also excluded from the study.

For control group Inclusion Criteria

• no known acute, subacute or chronic disease history
• not suffer from any infection in the last fortnight,
• not to be on a particular medication,
• Presenting to the ED with reasons other than infectious complaints
• Giving written consent to participate in the study.

Exclusion Criteria:

• diagnosis of kidney or liver failure
• acute pulmonary embolism
• chronic inflammatory disease history (rheumatological disease, autoimmune disease),
• pregnancy
• presence of any cancer diagnosis
• chronic obstructive pulmonary disease
• asthma disease,
• history of cerebrovascular disease.

After the required information concerning the study was provided both to the patient group and to the healthy control group, the written consent forms were obtained from all the subjects who agreed to participate in the study.

Once these subjects were assessed in accordance with the inclusion and exclusion criteria. Patients who were diagnosed with Covid-19 infection according to WHO guideline as a result of clinical evaluation in the emergency department and whose diagnosis was confirmed by RT-PCR were included in the study.

The healthy volunteers with no known chronic or acute disease or drug use as well as no recent history of infection were included study as the control group. Once these subjects were assessed in accordance with the inclusion and exclusion criteria, they were divided into four groups as the CT (-), PCR (+) SARS-CoV-2 infection group, Covid-19 (+) Pneumonia Group, CT (+), PCR (-) Suspected Pneumonia Group and Healthy group (Control Group).

There is no plan for sharing the patient datas.