A method for measuring the presence of calprotectin (S100A8/A) heterodimer in a biological sample using a particle-enhanced turbidimetric immunoassay (PETIA) based on monoclonal antibodies. The method can be adapted on automated standard analyzers and provides a reliable clinical measurement of calprotectin in faecal samples and extracts. The method is comparable to commerical two-site sandwich ELISA. The disclosed method counters spontaneous agglutination caused by calcium ions and low-molecular weight calcium-binding S100 proteins as observed with conventional PETIAs. The method can be used for measuring the presence of human calprotectin in stool, urine, serum, plasma, synovial liquid and other body liquids. Metrological traceability and high commutability with conventional immunoassays (ELISA) has been shown despite of different measurement principles used.