CXCL9 and hemophagocytic syndrome: Second, because MS is not an ideal technique for quantifying cytokines, most of which have low molecular weight and provide few peptides for MS detection [30, 31], we could not validate previous findings regarding the diagnostic value of cytokines for HLH (e.g., IFN-γ, CXCL9, IL6, and IL-10 [4, 8]).