[Correlation between serum nitric oxide synthase levels and readmission due to acute exacerbation within 30 days in patients with acute exacerbations of chronic obstructive pulmonary disease].

Objective: To explore the correlation between serum nitric oxide synthase (NOS) levels and readmission due to acute exacerbation within 30 days in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Methods: A prospective cohort study was conducted. The AECOPD patients admitted to the First Affiliated Hospital of Hebei North University from January 2020 to December 2022 were enrolled as the research subjects. The general data such as gender, age, body mass index (BMI), chronic obstructive pulmonary disease (COPD) course, smoking history, and basic diseases were collected. The laboratory indicators, serum NOS level [inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS)] and acute physiology and chronic health evaluation II (APACHE II) score within 24 hours after admission and total length of hospital stay were also collected, and whether patients were readmitted due to acute exacerbation within 30 days after discharge were recorded. The differences in the above clinical indexes between the readmitted and non-readmitted patients within 30 days were compared. Multivariate Logistic regression analysis was used to screen the influencing factors of readmission within 30 days after discharge in AECOPD patients. Receiver operator characteristic curve (ROC curve) was drawn to analyze the predictive value of various influencing factors on readmission.

Results: A total of 168 patients were enrolled, 38 patients were readmitted due to acute aggravation within 30 days after discharge, and 130 were not readmitted. Compared with the non-readmission group, the levels of white blood cell count (WBC), C-reactive protein (CRP), APACHE II score, and serum iNOS and eNOS levels within 24 hours after admission in the readmission group were significantly increased [WBC (×10⁹/L): 14.19 (12.88, 16.12) vs. 11.81 (10.63, 14.11), CRP (mg/L): 51.41±12.35 vs. 40.12±7.79, APACHE II score: 22.0 (19.0, 25.0) vs. 18.0 (14.0,20.5), iNOS (μg/L): 5.87±1.36 vs. 4.52±0.89, eNOS (μg/L): 4.40±1.00 vs. 3.51±1.08, all P < 0.01], and the levels of hemoglobin (Hb) and albumin (Alb) were significantly decreased [Hb (g/L): 108.82±22.06 vs. 123.98±24.26, Alb (g/L): 30.28±3.27 vs. 33.68±2.76, both P < 0.01]. There were no significant differences in gender, age, BMI, COPD course, smoking history, basic diseases, total length of hospital stay and serum nNOS level between the two groups. Multivariate Logistic regression analysis showed that CRP [odds ratio (OR) = 1.201, 95% confidence interval (95%CI) was 1.075-1.341], APACHE II score (OR = 1.335, 95%CI was 1.120-1.590), and serum iNOS (OR = 5.496, 95%CI was 2.143-14.095) and eNOS (OR = 3.366, 95%CI was 1.272-8.090) were the independent risk factors for readmission within 30 days after discharge in AECOPD patients (all P < 0.05), and Hb (OR = 0.965, 95%CI was 0.933-0.997) and Alb (OR = 0.551, 95%CI was 0.380-0.799) were protective factors (both P < 0.05). ROC curve analysis showed that serum iNOS and eNOS levels had predictive value for readmission within 30 days after discharge in AECOPD patients, and the area under the ROC curve (AUC) was 0.791 (95%CI was 0.694-0.887) and 0.742 (95%CI was 0.660-0.823), respectively. When the optimal cut-off value was 5.22 μg/L and 3.82 μg/L, the sensitivity was 81.54% and 69.23%, and the specificity was 71.05% and 81.58%, respectively. The AUC of serum iNOS and eNOS levels combined with Hb, Alb, CRP and APACHE II score for predicting the readmission was 0.979 (95%CI was 0.958-1.000), the sensitivity was 91.54%, and the specificity was 97.37%.

Conclusions: The increased serum iNOS and eNOS levels of AECOPD patients correlate with the readmission due to acute exacerbation within 30 days after discharge. Combined detection of Hb, Alb, CRP, serum iNOS and eNOS levels, and evaluation of APACHE II score within 24 hours after admission can effectively predict readmission.