An L-shaped curve relating Hs-CRP/HDL-C(CHR) index to kidney stone disease (KSD) in US adult participants: a cross-sectional study

Using 2015-2020 NHANES data, this cross‑sectional study examined the association between the Hs‑CRP/HDL‑C index (CHR) and adult kidney stone disease (KSD) and its potential nonlinear dose-response pattern. Weighted multivariable logistic regression and spline analyses were applied. Overall KSD risk was 10%; CHR showed a positive association with KSD odds (OR = 1.04, 95% CI = 1.01-1.08, <i>P</i> < 0.05). Smooth curves revealed an L‑shaped relationship (<i>P</i> for nonlinearity <0.05), with a steep increase when CHR <0.358, then plateauing. An interaction with albumin level was observed (<i>P</i> < 0.05); subgroup analyses by age, sex, BMI, smoking, alcohol, and triglycerides showed no significant differences. These findings suggest CHR may aid KSD risk assessment, but prospective studies are needed to confirm causality and temporal sequence.