Ans: D. Hematocrit(Ref: Harrison 19/e p1319, 1322)In a patient with dengue hemorrhagic fever (DHF), hematocrit is most impoant parameter to monitor. Diagnosis of DHF needs the presence of rise in hematocrit 420% or more i.e. Hemoconcentration.Despite the name, the critical feature that distinguishes DHF from dengue fever is not hemorrhaging, but rather plasma leakage resulting from increased vascular permeability