The present invention relates to a method of diagnosing bacterial or fungal sepsis in a subject, which method comprises the step of measuring the level of TREM-1-Ligand or TREM-1-Ligand nucleic acid in a biological sample obtained from said subject. The method can involve contacting said biological sample with a compound capable of binding TREM-1-Ligand and detecting the level of TREM-1-Ligand present in the sample by observing the level of binding between said compound and TREM-1-Ligand. Compounds, compositions and kits for use in the diagnosis of bacterial or fungal sepsis are also provided.