The relationship between the systemic immune-inflammation index and hepatitis C virus infection: NHANES 2005 to 2012

The systemic immune-inflammation index (SII), a contemporary biomarker indicative of inflammatory processes, captures the localized immune reactions and systemic inflammatory responses within the human body. Evidence has established correlations between SII and the incidence as well as the gravity of a range of hepatic pathologies. Nonetheless, the extant literature presents a paucity of studies exploring the SII's role and its clinical significance in the context of hepatitis C virus (HCV) infection. The objective of this research is to scrutinize the correlation between SII and HCV infection. Our research utilized data extracted from the national health and nutrition examination survey (NHANES). Owing to the asymmetric distribution of SII values, a natural logarithm transformation was implemented to achieve a more normal distribution. A Logit regression analysis was employed to assess the relationship between the natural logarithm of the SII (LN SII) and HCV infection. This cross-sectional analysis included 29,546 participants from 4 cycles of NHANES data. The results of the Logit model indicated that lower values of LN SII were linked to a higher probability of HCV infection. This relationship remained significant in the fully adjusted model (OR = 0.455; 95% CI: 0.381-0.543, P <.001). Furthermore, the analysis of the smoothly fitted curve unveiled a relationship resembling an inverted U-shape between LN SII and HCV infection, featuring a turning point value of 6.12. This study established a link between lower LN SII levels and the occurrence of HCV infection. To validate these findings, further large-scale and prospective studies are required.