Association of Neutrophil-to-Lymphocyte Ratio and Systemic Immune-Inflammation Index With Mortality in Patients With Pericarditis: A Retrospective Dual-Cohort Study Using Two Independent Databases
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Background
Risk stratification in pericarditis relies mainly on clinical presentation, suspected etiology, imaging findings, and conventional inflammatory biomarkers. Whether complete blood count–derived inflammatory indices are associated with mortality in pericarditis and reproducible across independent real-world datasets remains unclear.
Methods
We conducted a retrospective dual-cohort study of hospitalized adults with pericarditis using a Hong Kong cohort from the Clinical Data Analysis and Reporting System (CDARS) as the primary analysis cohort and the Medical Information Mart for Intensive Care IV (MIMIC-IV) cohort as an independent reproducibility cohort. Baseline neutrophil-to-lymphocyte ratio (NLR) and systemic immune-inflammation index (SII) were analyzed as continuous variables and cohort-specific tertiles. The primary outcome was long-term all-cause mortality in the Hong Kong cohort. Secondary and reproducibility outcomes included 90-day mortality in the Hong Kong cohort and 30-day, 90-day, and observable follow-up mortality in MIMIC-IV. Cox models were adjusted for age, sex, renal disease, diabetes mellitus, hypertension, ischemic heart disease, and malignancy.
Results
Among 504 patients in the Hong Kong cohort and 464 patients in MIMIC-IV, all-cause mortality occurred in 241 and 113 patients during cohort-specific follow-up, respectively. In the Hong Kong cohort, higher NLR was associated with long-term all-cause mortality after full adjustment. Compared with NLR tertile 1, the adjusted hazard ratio was 1.60 for tertile 3. Higher SII was also associated with long-term mortality, with an adjusted hazard ratio of 1.55 for tertile 3 versus tertile 1. NLR and SII showed directionally consistent associations with 90-day mortality in the Hong Kong cohort and with 30-day, 90-day, and observable follow-up mortality in MIMIC-IV. Sensitivity analyses yielded broadly consistent findings.
Conclusions
In two independent real-world cohorts of hospitalized patients with pericarditis, higher baseline NLR and SII were associated with increased all-cause mortality, with NLR showing the more consistent prognostic signal. These complete blood count-derived indices may provide simple adjunctive information for mortality risk stratification, although prospective validation is needed before incorporation into formal management algorithms.
