Platelet-to-lymphocyte ratio as an early predictor of colistin-induced nephrotoxicity in ICU patients with sepsis: a prospective cohort study

Background Critically ill patients have a nephrotoxicity rate of 30–60% with colistin, a polymyxin antibiotic reserved for carbapenem-resistant Gram-negative infections. The gold standard to monitor renal function is serum creatinine, which increases only after significant injury to the renal parenchyma has already occurred and so it offers a little window for intervention. Platelet-to-lymphocyte ratio (PLR), an inexpensive, routinely available inflammatory index, captures lymphocyte apoptosis and platelet dysregulation, two features of sepsis-related immunopathology. We hypothesized that the PLR measured at 48 h postinitiation of colistin on day 2 would serve as an early and independent predictor of colistin-induced acute kidney injury (CI-AKI). Patients and methods A prospective observational cohort study was conducted on a critical care unit at a tertiary level over 72 patients who were on colistin through the intravenous route in adults with sepsis. With the help of kidney disease: Improving Global Outcomes 2012 criteria AKI was defined. Laboratory parameters, including total leukocyte count, absolute lymphocyte count, and platelet count, at Day 0 (before initiation of colistin) and Day 2. The PLR was calculated at both points and categorized as PLR. The Mann–Whitney U test and Independent-samples t -test were used for group comparisons. The researchers performed logistic regression to find the independent predictors of CI-AKI. We calculated the predictive accuracy using receiver operating characteristic analysis with Youden’s index. Results In 31 (43.1%) patients, CI-AKI developed. On Day 0, there was no significant difference in PLR between the AKI group and the non-AKI group ( P =0.136). On Day 2, the PLR of the AKI group was substantially higher (283.5 ± 101.5 vs. 207.3 ± 73.6; P <0.001), due to a decline in lymphocyte count by 45% and platelet count by 30%. After controlling for age, sequential organ failure assessment score, and baseline creatinine, multivariable logistic regression showed that PLR at Day 2 was the strongest independent predictor of CI-AKI (OR 3.07; 95% CI: 1.52–6.23; P =0.002). An area under the curve of 0.769 was produced by receiver operating characteristic analysis. The best cutoff for PLR is greater than or equal to 229.1 with Sensitivity of 71.0%, Specificity of 80.5%, Positive predictive value of 73.3%, and Negative predictive value of 78.6%. Conclusions PLR at Day 2 after colistin initiation is an early, independent predictor of CI-AKI in ICU patients diagnosed with sepsis, demonstrating good discriminative performance. Its measurement requires no additional cost beyond routine complete blood counts. Prospective validation and integration with novel renal damage biomarkers are warranted to define its clinical role in nephrotoxicity surveillance protocols.