Diagnostic value of C-reactive protein-to-lymphocyte ratio combined with ultrasound features for complicated appendicitis: a retrospective cohort study

To investigate the association between the C-reactive protein-to-lymphocyte ratio (CLR) and the risk of complicated appendicitis, and to evaluate its incremental diagnostic value over conventional ultrasound features. In this retrospective cohort study, 230 patients with ultrasound-diagnosed appendicitis between December 2021 and February 2024 were included. Complicated appendicitis was confirmed by postoperative pathology. Associations were assessed using logistic regression. The diagnostic performance of a model with five ultrasound features was compared to a model adding ln CLR using ROC curve analysis and the DeLong test. Among 230 patients, 34 (14.8%) were identified as having complicated appendicitis. Higher ln CLR showed an independent association with an increased risk, with an adjusted odds ratio of 2.54 (95% CI: 1.47–4.41, p = 0.001). Patients in the lowest CLR tertile appeared to have a higher adjusted odds compared with those in the highest tertile (OR = 5.14, 95% CI: 1.18–22.36, p = 0.029). The ultrasound-only model yielded an area under the curve (AUC) of 0.872 (95% CI: 0.816–0.928). The addition of ln CLR was associated with a modest improvement in diagnostic performance, with the AUC increasing to 0.911 (95% CI: 0.868–0.954, p = 0.047). CLR may be independently associated with complicated appendicitis. The integration of CLR with ultrasound features appears to enhance diagnostic accuracy, suggesting that this combined approach could offer a practical tool for preoperative risk stratification.