Monocyte-to-Lymphocyte Ratio and Cardiovascular Outcomes in Individuals with Chronic Kidney Disease: A Systematic Review of Observational Studies

Abstract

ABSTRACT Introduction Inflammation contributes to increasing cardiovascular risk, especially in chronic conditions like chronic kidney disease (CKD). The monocyte-to-lymphocyte ratio (MLR) is a composite marker of inflammation. However, it remains relatively underexplored compared to other biomarkers. This study aimed to assess the MLR in relation to cardiovascular outcomes in CKD. Methods We systematically searched Medline, EMBASE, Web of Science, and Scopus from inception to May 28, 2025. We included peer-reviewed observational studies assessing MLR and cardiovascular outcomes or all-cause death in CKD. Two reviewers independently screened studies, extracted data, and assessed risk of bias using the Newcastle-Ottawa Scale. Findings were narratively synthesized. Results Eleven studies (n = 18,631) met our inclusion criteria. The study population ranged from non-dialysis CKD to end-stage kidney disease on dialysis, with follow-up from 1 to 124 months. Five studies (n = 16,974) examined cardiovascular death and generally reported significant associations with elevated MLR. Six studies (n = 4,587) assessed cardiovascular events except death, yielding inconsistent findings, although some reported significant associations. Five studies (n = 15,682) showed increased risk of all-cause death with increasing MLR. All except one of the eleven studies were rated as good quality. Conclusion Elevated MLR appears to be consistently associated with increased cardiovascular and all-cause death in CKD. Evidence for cardiovascular events remains inconsistent, and thresholds proposed in individual studies may not be generalizable. Large-scale, multi-ethnic, and prospective studies with standardized protocols are needed to validate MLR’s role in cardiovascular risk stratification.