Eosinophilia: workup and management

1.5 ×10⁹/L: the 2011 paper writes marked eosinophilia as ">1.5"; the 2023 Table 1 writes HE as "≥1.5". The tool uses ≥1.5, the more cautious reading.

0.5 ×10⁹/L: eosinophilia is ">0.5", but the mild band starts at 0.5. The tool counts 500/µL as mild eosinophilia, the cautious reading.

5.0 ×10⁹/L: the source is explicit: moderate is 1.5–5.0 and severe is above 5.0. So 5,000/µL is moderate and 5,001/µL is severe.

Bands are judged on the count rounded to a whole cell/µL (3 decimals in ×10⁹/L). Toggling units changes only the display. BSH calls 0.5–1.5 ×10⁹/L "mild to moderate" [BSH17]; the tool's labels follow ICOG-EO 2023.

Before steroids: check Strongyloides serology before corticosteroids or immunosuppression in anyone who has lived in an endemic region. If it is positive, treat before starting steroids [BSH17 Table III]. Serology can be falsely negative in immunocompromised patients, and stool microscopy is relatively insensitive [BSH17 Table III]. The tool treats an unknown immune status, and planned or started steroids, as immunocompromise. After a negative result in an immunocompetent patient, BSH Table III does not require cover before steroids (it asks for treatment when serology is positive). The exception is steroids needed now with a strong possibility of exposure, where the BSH text advises concomitant empirical ivermectin.

Steroids that cannot wait: patients on corticosteroids who are at risk of Strongyloides should get concomitant ivermectin [BSH17, grade 1B]. The BSH text gives 200 µg/kg/day for 2 days.

Treatment: the US label gives a single dose of about 200 µg/kg, with follow-up stool examinations. In immunocompromised hosts, repeated courses may be needed, for example at 2-week intervals; the optimal regimen is not established and cure may not be achievable [Label]. Get infectious-diseases advice.

Loa loa: heavy Loa loa infection can cause serious or fatal encephalopathy after a microfilaricide. After significant exposure to West or Central Africa, assess for loiasis before ivermectin and follow up carefully afterwards [Label]. Tests: filaria serology and day or night blood smears, timed for the species [BSH17 Table III].

Pregnancy and breastfeeding: the US label says ivermectin should not be used in pregnancy because its safety has not been established. In breastfeeding, treat only when the risk of delaying treatment outweighs the risk to the newborn [Label]. Albendazole may cause fetal harm; the label asks for a pregnancy test before prescribing it, and the tool shows no albendazole regimen [Label 5.2].

DRESS: in the prospective RegiSCAR series, the main features besides rash were eosinophilia (95%), visceral involvement (91%), high fever (90%), atypical lymphocytes (67%), mild mucosal involvement (56%) and lymphadenopathy (54%). Median onset was 22 days after the drug (IQR 17–31) [Kardaun13]. BSH puts onset at 3–6 weeks after a new drug [BSH17]. The 2024 Delphi consensus accepted immediate cessation of the culprit drug(s) for all patients. It recommends an ECG in all, with troponin and BNP only for suspected cardiac involvement, and EBV, CMV and HHV-6 viral loads in all. It treats any other organ damage as severe. Corticosteroids are the cornerstone of treatment; there is no consensus on dose, taper or duration [DRESS24].

The RegiSCAR score and the DRESS severity thresholds could not be checked in their primary text, so the tool shows red flags rather than a score.

EGPA: test ANCA in every patient with suspected EGPA. ANCA is detectable in 30–40%, mostly MPO-ANCA [EGPA23 statement 4, grade B]. The workup should cover heart, lung, skin, kidney and nerve involvement [EGPA23 statement 3, grade C]. The 2022 ACR/EULAR criteria score a patient already diagnosed with small- or medium-vessel vasculitis. Points are: eosinophils ≥1 ×10⁹/L +5, obstructive airway disease +3, nasal polyps +3, extravascular eosinophil-predominant inflammation +2, mononeuritis multiplex or motor neuropathy +1, cANCA or PR3-ANCA −3, hematuria −1. A total of 6 or more classifies EGPA [ACR/EULAR22]. These are classification criteria, not diagnostic criteria.

• Children and adolescents. The tool is for adults only.
• Pregnancy, beyond the ivermectin and imatinib holds.
• Kidney or liver dose adjustment. Imatinib: 50% lower starting dose at creatinine clearance 20–39 mL/min, and hepatic steps [Label 2.12]. Check every label.
• EGPA treatment, including mepolizumab for EGPA, which is a separate indication [Label 1.4]. Refer to rheumatology.
• Myeloid neoplasms other than FIP1L1::PDGFRA: PDGFRB, FGFR1, JAK2 and FLT3 fusions; CEL; systemic mastocytosis; CML.
• Eosinophilic esophagitis and other primary GI eosinophilic disorders, ABPA, eosinophilic pneumonias, and drug-specific AIN.
• Strongyloides hyperinfection, and parasite regimens other than Strongyloides and schistosomiasis. Get ID or tropical-medicine advice.
• The RegiSCAR score, DRESS severity thresholds and DRESS steroid dosing.
• The UK British Infection Association travel-eosinophilia guideline (J Infect 2025;90:106328), which could not be opened reproducibly and is not used.
• Monitoring intervals for asymptomatic patients; no source used here sets one.