Evaluation of the relationship between YKL-40 level and clinical severity in patients with Crimean-Congo hemorrhagic fever.

Crimean-Congo hemorrhagic fever (CCHF) is a widespread tick-borne viral disease. YKL-40 (also known as chitinase-3-like-1 protein) is an acute phase protein released by various immune cells. The purpose of this study was to investigate the relationship between YKL-40 level and the clinical course and prognosis of CCHF. The study included 78 patients who were admitted to our hospital between April 15 and 30 August 2022 and had a positive polymerase chain reaction test result for CCHF. The patients were divided into two groups, severe and non-severe. In addition, a control group consisting of 22 healthy people was established. Mean serum YKL-40 levels were significantly higher in patients than controls (106.8 ng/mL ± 91.2 and 47.1 ng/mL ± 35.3, respectively;  < 0.001). However, mean YKL-40 levels were also significantly higher in patients with severe CCHF compared to non-severe cases (173.3 ± 112.3 and 67.5 ± 41.7, respectively;  < 0.001). A comparison of the 10 exitus patients and the 68 survivors revealed significantly higher YKL-40 levels in the exitus group (mean: 214.0 ± 139.0 and 92.8 ± 73.6, respectively;  = 0.001). A receiver operating characteristic analysis for YKL-40 levels to distinguish between severe and non-severe patients found an area under the curve of 0.925. YKL-40 levels were measured with a sensitivity of 97% and a specificity of 84% with a cutoff value of 90.7 ng/mL. YKL-40 levels measured at the time of hospital presentation in patients with CCHF can be used as a biomarker for clinical course and prognosis.