Abstract: The invention relates to a method for determining a predictive function for discriminating patients according to their disease activity status, comprising steps of: a—measuring values of biological markers for each patient of a first group of patients having a first known disease activity status, and for each patient of a second group of patients having a second known disease activity status, the measured values forming a dataset b—analyzing the dataset for identifying biological markers which are differentially expressed between the first group of patients and the second group of patients, c—among the biological markers identified at step b, determining correlated markers as markers which are correlated with other markers above a predetermined significance level, d—removing from the dataset, values measured for a biological marker identified as correlated marker, e—analyzing the dataset obtained at step d for determining a predictive function that predicts a disease activity status of a patient as a combinat