Rich, Jennifer

Abstract Background Human granulocytic anaplasmosis (HGA) can cause severe illness requiring intensive care, but factors associated with critical illness among hospitalized patients are incompletely described. Method We performed a retrospective multicenter cohort study of adults hospitalized with PCR-confirmed HGA at Mayo Clinic Rochester and affiliated Mayo Clinic Health System sites in Minnesota and Wisconsin from 2014 through 2024. Patients who required ICU-level care were compared with those managed on general medical wards using exploratory univariate analyses (Fisher exact and Kruskal–Wallis tests). Results Among 101 hospitalized patients, 12 (12%) required ICU-level care. Symptoms documented at hospital presentation/admission were more frequent in ICU patients, including vomiting (64% vs 30%) and abdominal pain (55% vs 26%). On admission, ICU patients had lower sodium (mean 128.8 vs 132.3 mmol/L) and higher total bilirubin (mean 1.3 vs 0.8 mg/dL). Platelet nadir during hospitalization was lower in ICU patients (mean 54.8 × 109/L vs 84.1 × 109/L). Peak ferritin, measured in a subset, was markedly higher in ICU patients (median 21 666 vs 961 µg/L). The composite endpoint of HGA-related complications or serious treatment-related adverse events occurred more often in ICU patients (75% vs 17%); one death occurred in the ICU group. Conclusions In hospitalized adults with HGA, ICU-level care was associated with gastrointestinal symptoms at presentation/admission, admission hyponatremia and hyperbilirubinemia, lower platelet nadir, and marked hyperferritinemia when measured. Because these findings were derived from univariate group-level comparisons with substantial overlap between groups, they should be viewed as hypothesis-generating rather than individually predictive or sufficient as stand-alone triage criteria.