Objective: This study aimed to explore the relationship between neutrophil-to-lymphocyte ratio (NLR) and (neutrophil + monocyte)-to-lymphocyte ratio (NMLR) levels and the prevalence of immune thrombocytopenia (ITP) as well as all-cause mortality among adult ITP patients. Methods: This study used cross-sectional data from participants in the National Health and Nutrition Examination Survey (NHANES) between 2003 and 2018. The causes of death and mortality status of the participants were obtained from the National Death Index records. Logistic regression was used to explore the association between NLR and NMLR and ITP. Additionally, multivariable Cox proportional hazards regression models were employed to evaluate the association between NLR and NMLR and all-cause mortality in ITP patients. Results: A total of 36193 participants were included. Multivariate regression models revealed that NLR and NMLR were significantly associated with ITP (NLR: OR = 1.26, 95% CI: 1.14–1.40; NMLR: OR = 1.26, 95% CI: 1.15–1.38) after adjusting for all covariates. Notably, subgroup analysis revealed significant associations in males and hypertensive patients (P<0.05). Multivariable Cox proportional hazards regression models demonstrates that elevated levels of both NLR and NMLR are significantly associated with increased all-cause mortality in ITP patients, even after adjustment for all covariates, with NLR (HR = 1.22, 95% CI: 1.00–1.48) and NMLR (HR = 1.21, 95% CI: 1.01–1.45) retaining significant predictive value. Conclusions: Our study reveals that NLR and NMLR were significantly associated with ITP. Furthermore, elevated NLR and NMLR levels were significantly associated with increased all-cause mortality in ITP patients.

Immune Thrombocytopenia, Inflammation, All-Cause Mortality, Cross-Sectional Study, NHANES