Abstract: The invention discloses a method for identifying a subset of polynucleotides from an initial set of polynucleotides corresponding to the human genome for the in vitro determination of severity of the host response of a patient having a severe infectious and/or inflammatory condition, in a sample, a measuring device comprising a plurality of different gene probes which represent the entire human genome, the test persons, depending on their infectious and/or inflammatory status, are divided into at least two clinically determined phenotype groups, changes of the gene expression signals between the phenotype groups are compared statistically, and gene probes are selected based on the gene expression signals which have significantly changed statistically between at least two phenotype groups.