The Association Between the Aggregate Index of Systemic Inflammation ( <scp>AISI</scp> ) and Prevalence of Psoriasis: Cross Sectional <scp>NHANES</scp> Study 2003–2006 and 2009–2014

The aggregate index of systemic inflammation (AISI), calculated from monocyte, neutrophil, lymphocyte, and platelet counts, is a blood-count-derived composite marker of systemic inflammation. This cross-sectional study aimed to examine the association between AISI and the prevalence of psoriasis among U.S. adults. The dataset was obtained from the National Health and Nutrition Examination Survey (NHANES) database from 2003 to 2006 and from 2009 to 2014. The relevant covariates were adjusted during the analysis. We employed restricted cubic spline (RCS) regression and logistic regression frameworks to statistically assess the correlation between the AISI standard and psoriasis. The study also included subgroup analyses to determine whether the effectiveness of AISI varied among different categories. Compared with individuals without psoriasis, participants with psoriasis had higher AISI values. A total of 17 776 participants were included in the analysis. In multivariable logistic regression analyses, higher AISI levels were independently associated with higher odds of prevalent psoriasis after adjustment for potential confounders (p for trend < 0.001). Restricted cubic spline analyses demonstrated an approximately linear positive association between ln-transformed AISI and psoriasis prevalence (p for non-linearity > 0.05). Subgroup analyses showed no statistically significant interactions across most strata, suggesting overall consistency of the association. Receiver operating characteristic analysis indicated that AISI had limited discriminatory ability for prevalent psoriasis, with an AUC (95% CI) of 0.58 (0.55-0.60). In this large, population-based cross-sectional study, higher AISI levels were associated with the prevalence of psoriasis among U.S. adults. Given the cross-sectional design and the modest discriminatory ability (AUC = 0.58), AISI is best interpreted as a correlate of systemic inflammation rather than as a marker with predictive or causal utility for psoriasis.