Platelet-to-Lymphocyte Ratio and In-Hospital Mortality in Patients With AKI Receiving Continuous Kidney Replacement Therapy: A Retrospective Observational Cohort Study

Rationale & Objective: The platelet-to-lymphocyte ratio (PLR) is a marker of inflammation and a predictor of mortality in a variety of diseases. However, the effectiveness of PLR as a predictor of mortality in patients with severe acute kidney injury (AKI) is uncertain. We evaluated the association between the PLR and mortality in critically ill patients with severe AKI who underwent continuous kidney replacement therapy (CKRT).

Study Design: Retrospective cohort study.

Setting & Participants: A total of 1,044 patients who underwent CKRT in a single center, from February 2017 to March 2021.

Exposures: PLR.

Outcomes: In-hospital mortality.

Analytical Approach: The study patients were classified into quintiles according to the PLR values. A Cox proportional hazards model was used to investigate the association between PLR and mortality.

Results: The PLR value was associated with in-hospital mortality in a nonlinear manner, showing a higher mortality at both ends of the PLR. The Kaplan-Meier curve revealed the highest mortality with the first and fifth quintiles, whereas the lowest mortality occurred with the third quintile. Compared with the third quintile, the first (adjusted HR, 1.94; 95% CI, 1.44-2.62;  < 0.001) and fifth (adjusted HR, 1.60; 95% CI, 1.18-2.18;  = 0.002) quintiles of the PLR group had a significantly higher in-hospital mortality rate. The first and fifth quintiles showed a consistently increased risk of 30- and 90-day mortality rates compared with those of the third quintile. In the subgroup analysis, the lower and higher PLR values were predictors of in-hospital mortality in patients with older age, of female sex, and with hypertension, diabetes, and higher Sequential Organ Failure Assessment score.

Limitations: There may be bias owing to the single-center retrospective nature of this study. We only had PLR values at the time of initiation of CKRT.

Conclusions: Both the lower and higher PLR values were independent predictors of in-hospital mortality in critically ill patients with severe AKI who underwent CKRT.