Diagnostic Accuracy of Infection Biomarkers in the Initial Investigation of Patients With Suspected Pneumonia

The aim of this study is to investigate the diagnostic and prognostic value of C-reactive protein (CRP), serum procalcitonin (PCT) and soluble urokinase plasminogen activator receptor (suPAR) in the initial investigation of patients acute hospitalized with suspected community-acquired-pneumonia (CAP)

Target pneumonia treatment should be initiated within a few hours, which is why early and accurate diagnosis is extremely important. Uncertain or delayed diagnosis will often lead to an overconsumption of broad-spectrum antibiotics, which contributes to increased development of resistant bacteria and thus threaten the treatment options of the future. Pneumonia diagnosis is primarily made today on the basis of clinical symptoms and findings in the form of cough, vomiting, chest pain, fever, shortness of breath, supplemented with X-ray of the lungs, relevant blood tests and analysis of expectoration. However, X-ray is an imprecise diagnostic tool. The diagnosis of CAP is challenged by nonspecific symptoms, uncertain diagnostic methods and waiting time for test results up to several days.

Therefore, numerous studies have investigated biomarkers that can possibly support the diagnosis of CAP. C-reactive protein (CRP) and serum procalcitonin (PCT) are biomarkers that may distinguish CAP from other causes of acute respiratory infections. The CRP biomarker has been endorsed as a guide for antibiotic treatment by the National Institute for Health and Care Excellence (NICE) and PCT was suggested by the American Infectious Diseases Society of America. Soluble urokinase plasminogen activator receptor (suPAR) has emerged as a potentially novel biomarker for inflammatory diseases including pneumonia. Several studies have highlighted suPAR as a significant prognostic mortality marker and strongly related to disease severity and worse outcome in a variety of conditions. It is also a promising biological marker in the diagnosis of CAP.

The diagnostic value of the optimal biomarkers for the diagnosis of CAP remains controversial. The investigators hypothesize that serum CRP, PTC and suPAR have an impact on diagnosing, prognosis, and treatment of patients with a verified community-acquired-pneumonia. The objectives of the study are:

* To identify the diagnostic accuracy of CRP, PCT and suPAR in community-acquired pneumonia
* To identify the prognostic value of CRP, PCT and suPAR in relation to adverse events

Eligibility Criteria:
Inclusion Criteria:

* Adult patients ≥ 18 years old
* Patients suspected with pneumonia by the attending physician. The physician will base his/her suspicion on e.g. clinical symptoms such as cough, increased sputum production, chest tightness, dyspnea and fever \> 38⁰C, and indication for chest x-ray

Exclusion Criteria:

* If the attending physician considers that participation will delay a life-saving treatment or patient needs direct transfer to the intensive care unit.
* Admission within the last 14 days
* Verified COVID-19 disease within 14 days before admission
* Pregnant women
* Severe immunodeficiencies: Primary immunodeficiencies and secondary immunodeficiencies (HIV positive CD4 \<200, Patients receiving immunosuppressive treatment (ATC L04A), Corticosteroid treatment (\>20 mg/day prednisone or equivalent for \>14 days within the last 30 days), Chemotherapy within 30 days)