Detection of hemophagocytosis using serum laboratory tests includes soluble interleukin 2 receptor alpha chain (sCD25) and soluble CD163 (sCD163), a high affinity scavenger receptor for hemoglobin-haptoglobin complexes (Figure 1), both of which may be elevated, thereby suggesting sCD25 and sCD163 to be more sensitive in detection of MAS. The gene discussed is CD163; the disease is Hemophagocytosis.