Clinically differential diagnosis of human granulocytic anaplasmosis and severe fever with thrombocytopenia syndrome

<strong>Objectives</strong> This study analyzed HGA and SFTS in patients with suspected tick-borne infection by focusing on key differences that clinicians can easily recognize. <strong>Methods</strong> A retrospective analysis was performed on confirmed patients with HGA or SFTS in 21 Korean hospitals from 2013 to 2020. A scoring system was developed by multivariate regression analysis and accuracy assessment of clinically easily discriminable parameters was performed. <strong>Results</strong> The multivariate logistic regression analysis revealed that sex-especially male sex (odds ratio [OR] 11.45, P=.012), neutropenia (&lt;1500) (OR 41.64, P&lt;.001), prolonged activated partial thromboplastin time (OR 80.133, P&lt;.001), and normal C-reactive protein concentration (≤1.0 mg/dL; OR 166.855, P=.001) were significantly associated with SFTS but not with HGA. Each factor, such as meaningful variables, was given 1 point, and a receiver-operating characteristic curve with a cutoff value (&gt;1) in a 5-point scoring system (0–4 points) was analyzed to evaluate the accuracy of differentiation between HGA and SFTS. The system showed 94.5% sensitivity, 92.6% specificity, and an area under the receiver-operating characteristic curve of 0.971 (0.949–0.9). <strong>Conclusions</strong> Where HGA and SFTS are endemic, the scoring system based on sex, neutrophil count, activated partial thromboplastin time, and C-reactive protein concentration is a test that can be quickly performed in the emergency room (ER) and administered to patients with suspected tick-borne infectious diseases. These diseases may be easily differentiated clinically using this model.