ObjectiveTo explore the diagnostic value of plasma C-C motif chemokine ligand 3（CCL3） levels in infectious diseases. MethodsThe study enrolled patients in hospital or outpatient service and individuals undergoing health check-ups at Guangdong Provincial People's Hospital from July to October 2023. Patients clinically diagnosed with infectious diseases were assigned to the experimental group， while those who were healthy or diagnosed with non-infectious diseases were included in the control group. After non-qualifying samples were excluded， residual blood specimens from complete blood count （CBC） tests were collected to measure the plasma CCL3 levels.The CBC parameters including white blood cell count （WBC）， neutrophils count （NEUT）， eosinophils count （EOS），etc， and the plasma CCL3 levels were analyzed between the infectious and control groups to evaluate the clinical diagnostic value of CCL3 in infectious diseases. ResultsA total of 257 cases were enrolled， with 167 in the experimental group （active infections confirmed via clinical symptoms， CBC， inflammatory markers， or etiological examinations） and 90 in the control group （confirmed absence of active infections）. The experimental group exhibited higher levels of WBC， NEUT and CCL3 than the control group， while the lymphocytes count（LYMPH）， EOS in the experimental group were lower， with statistical significance （P<0.001） in univariate analysis. By using these significantly different indicators as independent variables， logistics regression modeling identified WBC， NEUT and CCL3 as independent risk factors for infection. Receiver operating characteristic（ROC） curve analysis revealed superior diagnostic performance of CCL3 over WBC and NEUT， while LYMP and EOS showed no diagnostic performance. The area under the curve （AUC） for CCL3 was 0.844 （95% CI： 0.795， 0.892）， with a sensitivity of 84.4%， a specificity of 69.8%， and an optimal threshold of 106.405 ng/mL. ConclusionPlasma CCL3 levels have clinical diagnostic value in predicting infectious diseases and may serve as a potential clinical biomarker for detecting infectious diseases.