Inflammatory Markers and Contrast‐Induced Nephropathy Risk: A Meta‐Analysis of NLR and PLR in ACS Patients Undergoing Percutaneous Coronary Intervention

Background Contrast‐induced nephropathy (CIN) is a serious complication after percutaneous coronary intervention (PCI), especially in acute coronary syndrome (ACS) patients. While risk factors are known, predicting CIN remains difficult. New biomarkers like the neutrophil‐to‐lymphocyte ratio (NLR) and platelet‐to‐lymphocyte ratio (PLR) are gaining attention as potential predictors due to their links with inflammation and coagulation. Aims This meta‐analysis examines whether NLR and PLR can predict CIN risk in PCI patients with ACS, aiming to clarify their diagnostic value. Methods We analyzed data from 25 studies with 25,505 patients, looking at the link between preprocedural NLR and PLR and CIN risk. We calculated odds ratios (OR), sensitivity, specificity, and area under the curve (AUC) values to assess diagnostic accuracy. Results A total of 25,505 patients from 25 studies were included. Elevated preprocedural NLR and PLR were significantly associated with increased CIN risk. In the ACS population, 15 studies demonstrated that NLR was significantly associated with increased odds of CIN, with a pooled OR of 1.21 (95% confidence interval (CI): 1.12 to 1.30, p < 0.001). Receiver operating characteristic analysis showed moderate sensitivity (72%), specificity (60%), and an AUC of 71%. Similar trends were observed in ST‐segment elevation myocardial infarction (STEMI). The non‐STEMI (NSTEMI) subgroup showed a stronger association, with a pooled OR of 2.03 (95% CI: 1.13 to 3.65, p = 0.02), moderate to good diagnostic accuracy (AUC 79%), and higher sensitivity (77%) and specificity (73%). For PLR, significant associations with CIN were found in the ACS population (OR: 1.16, 95% CI: 1.04 to 1.30, p = 0.007), with moderate diagnostic accuracy (AUC: 0.67, 95% CI: 0.61 to 0.73). In the STEMI population, PLR was also significantly associated with CIN (OR: 1.34, 95% CI: 1.14 to 1.57, p < 0.001), but diagnostic accuracy was lower (AUC: 0.66, 95% CI: 0.59 to 0.74). Limited data from the NSTEMI population showed a moderate association (AUC: 0.68, 95% CI: 0.64 to 0.72), indicating fair diagnostic accuracy. Conclusion Preprocedural NLR and PLR are simple, cost‐effective biomarkers for predicting CIN risk in ACS, especially among NSTEMI patients undergoing PCI. These markers can facilitate earlier identification of high‐risk patients and enable targeted preventive strategies. However, their moderate diagnostic performance highlights the need for the development of more specific and sensitive biomarkers.