The aspects of the disclosed embodiments relate to method for determining a likelihood of an inflammatory gastrointestinal tract disease. The method includes diluting a biological sample of a human subject and contacting it with 8-anilinonaphthalene-1-sulfonic acid as modulating agent and further with a reagent, said reagent comprising a peroxidase enzyme and a label selected from a europium chloride and terbium chloride. The sample is incubated and excited, and the time-resolved luminescence signal of the label in the sample is measured. If the luminescence signal is at least 112% higher than for a control sample from a human so subject without of an inflammatory intestine disease, an increased likelihood of an inflammatory intestine disease of the human subject is determined.