Viruses (May 2022)

Development of a Scoring System to Differentiate Severe Fever with Thrombocytopenia Syndrome from Scrub Typhus

  • Hyoung Sul,
  • Na Ra Yun,
  • Dong-Min Kim,
  • Young Keun Kim,
  • Jieun Kim,
  • Jian Hur,
  • Sook In Jung,
  • Seong Yeol Ryu,
  • Ji Yeon Lee,
  • Kyungmin Huh,
  • Yee Gyung Kwak,
  • Hye Won Jeong,
  • Jung Yeon Heo,
  • Dong Sik Jung,
  • Sun Hee Lee,
  • Sun Hee Park,
  • Joon-Sup Yeom,
  • Hyungdon Lee

Journal volume & issue
Vol. 14, no. 5
p. 1093


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Severe fever with thrombocytopenia syndrome (SFTS) and scrub typhus are disorders with similar clinical features; therefore, differentiating between them is difficult. We retrospectively collected data from 183 SFTS and 178 scrub typhus patients and validated an existing scoring system to develop a more sensitive, specific, and objective scoring system. We first applied the scoring systems proposed by Kim et al. to differentiate SFTS from scrub typhus. Multivariable logistic regression revealed that altered mental status, leukopenia, prolonged activated partial thromboplastin time (aPTT), and normal C-reactive protein (CRP) level (≤1.0 mg/dL) were significantly associated with SFTS. We changed the normal CRP level from ≤1.0 mg/dL to ≤3.0 mg/dL and replaced altered mental status with the creatine kinase (CK) level. The modified scoring system showed 97% sensitivity and 96% specificity for SFTS (area under the curve (AUC): 0.983) and a higher accuracy than the original scoring system (p = 0.0308). This study’s scoring system had 97% sensitivity and 98% specificity for SFTS (AUC: 0.992) and a higher accuracy than Kim et al.’s original scoring system (p = 0.0308). Our scoring system that incorporated leukopenia, prolonged aPTT, normal CRP level (≤3.0 mg/dL), and elevated CK level (>1000 IU/L) easily differentiated SFTS from scrub typhus in an endemic area.