Table 2. Suggested adult M-HLH baseline work-up.

-Ferritin, coagulation panel with fibrinogen; LDH, lactate, triglyceride, beta2-microglobulin, CRP, CBC with diff, peripheral smear review, CMP: order STAT -Soluble IL2 receptor, cytokine panel (if available locally or as a send out), soluble CD163 -Cultures blood, urine, sputum, bronchoscopy -NK function and T-lymphocyte subsets by PB flow requisition -Pregnancy test -Serologies: EBV, CMV, HSV, acute hepatitis screen, parvovirus -Viral loads: EBV, CMV, HHV-6, HHV-8, HIV, parvovirus, adenovirus if prior alloSCT; -Other: Urine: histoplasmosis antigen; serum quantiferon DAT, ANA (other rheumatology work-up if indicated) Immunoglobulin panel (quantitative immune globulins, IgG subsets) Transferrin saturation: if elevated, HFE gene analysis -Imaging: PET-CT preferred over CT chest/abdomen/pelvis MRI brain, possibly spine -Biopsies (as clinically indicated to identify hemophagocytosis or diagnose/stage underlying tumor): Bone marrow aspiration and biopsies Lymph node aspiration by FNAC if palpable nodes, consider excisional biopsy Skin biopsies particularly if rash, livedo, skin lesions, normal vascular changes/red moles Liver biopsy (if HLH liver involvement features) Lumbar puncture (diagnostic and therapeutic) as soon as bleeding risk declines -Hypomorphic mutation genetic testing: to be ordered when HLH diagnosis confirmed (if available locally or as a send-out)

LDH, lactate dehydrogenase, CRP, C-reactive protein, CBC, complete blood count, CMP, comprehensive metabolic panel, NK, natural killer, DAT, direct antiglobulin testing, ANA, anti-nuclear antibody, HFE, human factors engineering, HLH, hemophagocytic lymphohistiocytosis