A study that evaluated PCT in neutropenic hematological patients with mucositis revealed that it represents an important tool to predict the occurrence of major infections in patients with febrile neutropenia, even in the presence of associated complicating conditions, such as mucositis and GVHD.29 A lower threshold value (e.g. PCT > 0.25 ng/mL) increases the diagnostic reliability in case of a serious infection, even in patients with neutropenia.30–31 This reduced increase may happen since the adhering monocytes, among other factors, are necessary for the induction of PCT. This evidence concerns the gene CALCA and graft versus host disease.