Abstract: Objective: To clarify the correlation between the prognostic nutritional index (PNI), neutrophil percentage-to-albumin ratio(NPAR), and disease activity in patients with systemic lupus erythematosus (SLE), and to evaluate their clinical application value. Methods: A total of 74 SLE patients admitted to the hospital from March 2020 to December 2024 were selected as the observation group. According to the SLE Disease Activity Index (SLEDAI), the patients were divided into the active group (SLEDAI ＞5 points, 36 cases) and the stable group (SLEDAI < 5 points, 38 cases). Additionally, 75 healthy individuals who underwent physical examinations during the same period were selected as the healthy control group. A hematology analyzer was used for five-category complete blood count, and a biochemical analyzer was employed to detect the serum albumin (ALB) level. PNI and NPAR were calculated and compared among the groups. Receiver operating characteristic (ROC) curves were plotted to analyze the sensitivity and specificity of the two indicators in the diagnosis of SLE, which were verified by diagnostic calibration curve. Meanwhile, a nomogram model was established to evaluate the predictive ability of the two indicators for SLE activity. Results: Compared with the healthy control group, the observation group had a lower PNI level and a higher NPAR level. Compared with the stable group, the SLE active group showed a significantly lower PNI level and a significantly higher NPAR level, with statistically significant differences (Ps＜0.001). Pearson correlation analysis revealed a negative correlation between PNI and NPAR levels in SLE patients (r=-0.789, P＜0.001). The areas under the ROC curve (AUC) of PNI and NPAR for diagnosing SLE were 0.954 and 0.957, respectively, with a sensitivity of 0.960 for both, and specificities of 0.919 and 0.905, respectively. For evaluating SLE activity, the AUC values of PNI and NPAR were 0.723 and 0.703, respectively, with a sensitivity of 0.789 for both. The nomogram model had a higher score, indicating a higher predicted risk, the nomogram model suggested that the C-index of PNI and NPAR used in SLE and its activity analysis were 0.967 (95% CI: 0.937-0.998) and 0.723 (95% CI: 0.606-0.840). Conclusion: The prognostic nutritional indicator PNI and the inflammatory-nutritional indicator NPAR have certain value in the diagnosis and activity assessment of systemic lupus erythematosus, and the established nomogram model exhibits good accuracy and discriminative ability.

Key words: systemic lupus erythematosus, PNI, NPAR