The diagnostic value of platelet-to-neutrophil ratio in diabetic macular edema.

Purpose: To evaluate the diagnostic value of platelet-to-neutrophil ratio (PNR) in the occurrence of diabetic macular edema (DME) in patients with diabetic retinopathy (DR).

Methods: This cross-sectional study included 366 participants categorized into four groups: DME group (n = 96), DR group (n = 90, DR without DME), diabetes mellitus (DM) group (n = 90, without DR), and healthy control group (n = 90). PNR was calculated by dividing the platelet count by the neutrophil count. Each subject was classified as one of three DME types according to the optical coherence tomography (OCT) features: diffuse retinal thickening (DRT), cystoid macular edema (CME), serous retinal detachment (SRD). The correlations between the PNR and the occurrence of DME, as well as the DME subtypes based on OCT were investigated. Multivariate logistic regression analysis was employed to determine the risk factors for DME. Receiver operating characteristic (ROC) curve analysis was conducted to assess the predictive value of PNR for DME.

Results: DME group exhibited significantly lower PNR level compared to the other three groups [50.73 (38.92, 65.20) in DME group, 95.63 (68.83, 120.19) in DR group, 92.39 (72.38, 130.61) in DM group, and 100.66 (75.26, 152.77) in healthy control group, respectively, p < 0.001], but did not differ across the DME subtypes based on OCT (p = 0.548). The ROC curve demonstrated that the PNR could better predict DME (area under the curve = 0.832, 95% confidence interval: 0.773 - 0.891, p < 0.001). When the cut-off value of the PNR was 68.51, the sensitivity was 80.2%, and the specificity was 75.6%. Multivariate regression analysis indicated that PNR ≤ 68.51 was an independent risk factor for DME occurrence in DR patients (Odds ratio = 12.05, 95% confidence interval: 5.93 - 24.47, p < 0.001).

Conclusion: PNR ≤ 68.51 was strongly associated with the development of DME in DR patients, while no significant differences in PNR levels were observed across the different OCT morphological groups. Hence, PNR may serve as a valuable diagnostic biomarker for identifying DME, thereby enhancing risk stratification and management strategies for patients with DR.