Abstract Background Early diagnosis of bacterial infections in critically ill patients is challenging, as the clinical manifestation is non-specific. Neutrophil activation is a major response to bacterial infection and calprotectin an important marker for neutrophil mediated inflammation. Earlier studies have shown the ability of calprotectin to predict bacterial infections before onset of clinical symptoms. With early diagnosis of bacterial infections delayed treatment will be avoided as well as deterioration due to severe infections/sepsis. Methods A decision tree model is employed to estimate the impact of calprotectin analysis for early detection of bacterial infection and thus, the earlier start of antibiotic treatment compared to other diagnostic comparators such are white blood cell count, procalcitonin, C-reactive protein, and no testing. The analysis is based on patients admitted to an ICU in a Swedish hospital. The model allows for different diagnostic outcomes based on correctly and incorrectly diagnosis of bacterial infection and timing of antibiotic treatment: patient survival, length of stay in ICU and in general ward and total costs. Results The base-case results show that predictively measuring of calprotectin in an ICU, using GCAL® assay reduces total costs by approximately 13 000–18 000 EUR per patient, overall mortality rate by 0.11, and mean length of stay in an ICU and general ward by 1.3–2 days and 6–8 days, respectively. Conclusion The base-case scenario identified GCAL® Calprotectin Immunoassay as cost-effective for a patient cohort presenting in a Swedish ICU. Compared to the comparators, GCAL® saves total costs, reduces the mean duration of in-patient care, and reduces in-hospital mortality in those patients. In the sensitivity analysis, when key model inputs are varied, GCAL® Calprotectin Immunoassay remains the dominant option.