Glutathione S-transferase, delta cycle threshold Delta cycle threshold for glutathione S-transferase (gst). Cycle threshold is the PCR cycle number at which the fluorescent signal of the gene being amplified crosses the set threshold. Delta cycle threshold for gst is the difference between the cycle threshold (Ct) of gst gene expression and the cycle threshold (Ct) for the gene expression of the reference gene (e.g., beta-actin). Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.