Contents lists available at ScienceDirect Ticks and Tick-borne Diseases journal homepage: www.elsevier.com/locate/ttbdis Original article Hitit Index to distinguish patients with and without Crimean-Congo hemorrhagic fever Huseyin Kayadibi a, ⁎ , Derya Yapar b , Ozlem Akdogan b , Nuray N Ulusu c , Nurcan Baykam b a Hitit University School of Medicine, Department of Medical Biochemistry, Corum, Turkey b Hitit University School of Medicine, Department of Infectious Diseases and Clinical Microbiology, Corum, Turkey c Koc University School of Medicine, Department of Medical Biochemistry, Istanbul, Turkey ARTICLE INFO Keywords: Crimean-Congo hemorrhagic fever Early diagnosis Hitit Index ABSTRACT Crimean-Congo hemorrhagic fever (CCHF) is fatal. Therefore, it is very important to use an inexpensive, easily accessible, quick and accurate screening index based on clinical signs and laboratory parameters to identify patients suspected of having CCHF. Laboratory test results on the day of hospitalization for 268 inpatients suspected of having CCHF were used to calculate the laboratory section of the Hitit Index, while 65 of these were also monitored daily during their hospital stay to develop the clinical section of the Hitit Index. Two-hundred CCHF-negative outpatients were also evaluated. One-hundred and forty-nine inpatients were CCHF-positive and 119 inpatients were CCHF-negative. The Hitit Index is 5.6 - (5.3*lymphocyte) - (0.02*fibrinogen) - (12*direct bilirubin) + (0.04*AST) + (0.32*hema- tocrit) - (0.5*neutrophil) - (0.07*CKD-EPI) - (0.001*CK) ± conjunctival hyperemia (+1.5 in conjunctival hyperemia presence and -1.5 in conjunctival hyperemia absence). In 65 inpatients monitored daily, Hitit Index results for CCHF-positive and negative inpatients were 6.10(1.90–12.30) and -5.35(-8.83– -1.95), while CCHF-negative outpatients were -10.99(-15.64– -6.95) (P < 0.001), respectively. On hospitalization day, just one inpatient was false-negative in 27 CCHF-positive inpatients, while four were false-positive among 38 CCHF-negative inpatients using the Hitit Index. After 24 h, just one inpatient was diagnosed falsely among 27 CCHF-positive and 38 CCHF-negative inpatients, and there was no change after 48 h. Management of patients living in endemic regions suspected of having CCHF could be achieved within minutes using the Hitit Index. Patients with Hitit Index less than zero can be monitored as outpatients, while patients with Hitit Index results above zero must be hospitalized in infectious diseases wards. This study was not registered since it was retrospective. 1. Introduction Crimean-Congo hemorrhagic fever virus (CCHFV), which is a member of the Orthonairovirus genus in the Nairoviridae family, causes Crimean-Congo hemorrhagic fever (CCHF) with an average mortality rate of 3–30% in humans. CCHFV is widespread in many regions of Africa, the Middle East and Eastern Europe to Russia (in more than 30 countries). It is usually transmitted to humans via ticks of the genus Hyalomma or by exposure to the blood or other body fluids of an in- fected animal or CCHF patient. CCHF in humans has clinical symptoms of fever, conjunctival hyperemia, facial hyperemia, headache, myalgia, dizziness, nausea, vomiting, and diarrhea and may affect every site of the body during the hemorrhagic period (Ergonul, 2006; Swanepoel et al., 1989). The distinguishing medical biochemistry laboratory features of CCHF are elevated liver and muscle enzymes such as alanine amino- transferase (ALT), aspartate aminotransferase (AST), lactate dehy- drogenase (LDH) and creatine kinase (CK); coagulation disorders such as thrombocytopenia, hypofibrinogenemia, prolonged activated partial thromboplastin time (aPTT) and prothrombin time (PT) or international normalized ratio (INR); and suppressed complete blood count in- flammatory parameters such as leukocyte, lymphocyte, neutrophil and monocyte. Bilirubin may also be an essential biomarker in CCHF due to anti-inflammatory and anti-oxidative effects (Ergonul, 2006; Zhu et al., 2010; Ergonul et al., 2004). CCHF infection has four distinct phases in humans: an incubation period, prehemorrhagic phase, hemorrhagic phase and the con- valescence phase (Ergonul, 2006; Ergonul et al., 2017). In this study, https://doi.org/10.1016/j.ttbdis.2019.05.010 Received 14 December 2018; Received in revised form 20 April 2019; Accepted 25 May 2019 ⁎ Corresponding author at: Hitit University School of Medicine, Department of Medical Biochemistry, Corum, Turkey. E-mail address: mdkayadibi@yahoo.com (H. Kayadibi). Ticks and Tick-borne Diseases xxx (xxxx) xxx–xxx 1877-959X/ © 2019 Elsevier GmbH. All rights reserved. Please cite this article as: Huseyin Kayadibi, et al., Ticks and Tick-borne Diseases, https://doi.org/10.1016/j.ttbdis.2019.05.010