Elevated inflammatory indicators derived from routine complete blood cell counts may be independently associated with higher all-cause mortality in patients with rheumatoid arthritis, according to a population-based study using National Health and Nutrition Examination Survey data from 2007 to 2018.
In the study, Liu et al included 1314 patients with rheumatoid arthritis (RA). The participants were followed for a median of 78 months, during which 246 deaths occurred. The investigators examined the systemic inflammatory response index (SIRI), neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), and platelet-to-lymphocyte ratio (PLR), all derived from routine complete blood cell counts.
After adjusting for covariates—including age, sex, race/ethnicity, marital status, education, income, diabetes, hypertension, smoking status, alcohol use, and body mass index—elevated SIRI, NLR, and MLR remained independently associated with increased mortality.
In fully adjusted models, the highest tertile of SIRI was associated with a hazard ratio (HR) of 1.87 (95% confidence interval [CI], 1.12-3.13), NLR with an HR of 1.79 (95% CI, 1.10-2.92), and MLR with an HR of 1.88 (95% CI, 1.17-3.02), each compared with their lowest tertiles.
Kaplan-Meier analysis demonstrated significantly lower survival among patients in the highest tertiles of SIRI, NLR, and MLR (P<.001 for all). In contrast, no statistically significant associations were observed for SII and PLR after full adjustment.
Restricted cubic spline analysis showed linear associations between SIRI, NLR, and MLR and all-cause mortality. Nonlinear relationships were observed for SII and PLR, with mortality increasing when log-transformed SII exceeded 5.82 (P=.03) and PLR exceeded 4.68 (P<.001).
The indices were calculated using the following formulas: SIRI = (neutrophil count × monocyte count)/lymphocyte count; NLR = neutrophil count/lymphocyte count; and MLR = monocyte count/lymphocyte count. These markers reflect the balance between innate immune activation and adaptive immune response.
Higher levels of SIRI, NLR, and MLR were more common in patients aged 60 years and older, male patients, and those with hypertension.
Prior studies have linked NLR and MLR to mortality in various populations; however, few have comprehensively evaluated these markers in RA. The investigators systematically assessed multiple complete blood cell count–derived indicators and their associations with mortality in a nationally representative RA cohort, representing the first comprehensive study of this type.
Limitations included the study's observational design, single-timepoint laboratory measurements, and the US-only population. Replication in other populations is warranted.
The findings suggested that complete blood cell count–derived markers such as SIRI, NLR, and MLR may serve as accessible prognostic indicators for long-term mortality risk in RA.
The authors declared no conflicts of interest.
Source: Frontiers in Medicine
