Correlations between free IL-18 concentrations and biologic markers in HPS patients. Correlations were studied between initial serum-free IL-18 concentrations and the various biologic markers of HPS such as hemoglobin (Hb), polymorphonuclear cells (PMNs), platelets (plt), ferritinemia, triglyceridemia (Tg), and LDH (*P < .05, **P < .01, ***P < .001; n = 21).