The purpose of this study is to determine the efficacy of C-reactive protein and procalcitonin based guidelines versus standard of care to reduce duration of antibiotic exposure in patients hospitalized with community acquired pneumonia.

BIO-CAP is a prospective randomized intervention study which aims to evaluate the efficacy of C-reactive protein (CRP) based guidelines and procalcitonin (PCT) based guidelines to reduce duration of antibiotic exposure in adult patients hospitalized with community-acquired pneumonia (CAP) compared to standard-of-care.

Hypothesis: the duration of antibiotic exposure can be reduced when a biomarker algorithm - in addition to standard of care - is used to stop antibiotic treatment.

1) CRP based guidelines can reduce duration of antibiotic exposure equally to procalcitonin based guidelines and 2) Either of these two biomarker algorithms ( CRP or PCT) are superior compared to standard of care.

Sample size. Preconditions: significance level (α) 5 % and power (β) 80 %. Test: unpaired T-test. Mean treatment time 11 days (SD 5) in this population. Relevant detection limit defined at 2 days. The bonferroni correction has been used to correct for the fact that 2 primary analysis will be performed, why α = 0.005/2 = 0.025. Estimated 100 patient in each arm, thus n = 300.

Site monitoring and auditing. The study is monitored by the unit for Good Clinical Practice, Bispebjerg Hospital, Denmark.

Inclusion Criteria:

• Patients 18 years of age or older admitted to hospital with community acquired pneumonia defined as a new infiltrate on x-ray and at least one of the following; cough, expectoration, dyspnea, fever and pathological lung-auscultation.
• Not admitted to hospital within the last 14 days
• The patients has been prescribed antibiotic treatment for pneumonia
• The patient can comprehend the written and verbal information and has provided written consent.

Exclusion Criteria:

• Patient are unable to give written consent or patient does not understand the Danish language.
• Active pulmonary tuberculosis
• Severe immunosuppression determined by the treating physician (i.e. treatment with highdose corticosteroid for more than 2 weeks, chemotherapy and neutropenia with neutrophils < 0.5x109/l, ongoing treatment with biological drugs, chronic HIV-infection with CD4 cell count < 350 mio./l, immunosuppression after organ transplantation).
• Pregnancy and breastfeeding
• Patients admitted to hospital and treated against their will.
• Terminal ill patients where active treatment is stopped within the first 48 hours of admission.
• Patients who are, from the date of inclusion, prescribed antibiotic treatment for more than 3 days on a different indication than pneumonia.