Figure. Diagnostic work-up for identifying patients with HES and EGPA^{4, 6, 22–24}.

^aBone marrow exam should be considered in the following situations: phenotyping and/or cytogenetic tests suggesting myeloid or lymphoid variant HES, blood eosinophilia >5000/mm³, elevated serum tryptase, lack of response to systemic corticosteroid treatment; ^btesting which can be performed on bone marrow; ^ca further category of potential diagnoses includes HE of undetermined significance, where unexplained hypereosinophilia is present but patients do not have associated eosinophil-related end organ damage or complications; this is not discussed further as it lies outside the scope of this review; ^deg, anemia/thrombocytopenia, splenomegaly, elevated serum vitamin B12/tryptase or lack of response to systemic corticosteroid therapy; ^ecurrent ACR/EULAR EGPA classification criteria require a total score ≥6 across the following seven criteria: obstructive airway disease (+3), nasal polyps (+3), mononeuritis multiplex (+1), blood eosinophil count ≥1 × 10⁹cells/L (+5), extravascular eosinophilic-predominant inflammation on biopsy (+2), positive test for cytoplasmic ANCA or anti-PR3 antibodies (−3), hematuria (−1).³⁶

ACR/EULAR, American college of rheumatology/European alliance of associations for rheumatology; ANCA, antineutrophil cytoplasmic antibody; CT, computed tomography; ECG, electrocardiogram; EGPA, eosinophilic granulomatosis with polyangiitis; FDG-PET, fluorodeoxyglucose-positron emission tomography; FGFR1, fibroblast growth factor receptor 1; HE, hypereosinophilia; HES, hypereosinophilic syndrome; IFN, interferon; Ig, immunoglobulin; JAK, Janus kinase; MPO, myeloperoxidase; MRI, magnetic resonance imaging; NGS, next-generation sequencing; NOS, not otherwise specified; PCR, polymerase chain reaction; PDGFRA, platelet-derived growth factor receptor alpha; PDGFRB, platelet-derived growth factor receptor beta; PR3, proteinase 3; TCR, T-cell receptor.