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. 2025 Feb 3;22(5):1072-1080.
doi: 10.7150/ijms.106118. eCollection 2025.

Serum legumain is a potential biomarker for community-acquired pneumonia: a prospective cohort study

Xian-Ling Meng  1   2 , Kai-Shu Ma  2 , Kai-Xin Qu  2 , Zhen-Yu Cheng  3   4 , Lin Fu  3   4   5 , Yi-Qing Qu  1
Affiliations

Serum legumain is a potential biomarker for community-acquired pneumonia: a prospective cohort study

Xian-Ling Meng et al. Int J Med Sci. .

Abstract

Background: Legumain is a cysteine endopeptidase that belongs to the C13 family. Many studies have revealed that legumain plays a vital pathogenic role in various respiratory diseases. The aim of this study was to explore the role of legumain in community-acquired pneumonia (CAP). Methods: Serum samples were collected from 293 CAP patients on admission. The concentration of serum legumain was detected via an enzyme-linked immunosorbent assay. The relationship between serum legumain and CAP was assessed. Results: Serum legumain concentrations were increased in severe CAP patients compared to the concentrations of mild CAP patients. The Spearman rank correlation coefficient suggested that the serum legumain concentration was strongly associated with many clinical indicators. Additionally, linear regression analysis revealed that the serum legumain concentration was positively correlated with the CURB-65, PSI, SMART-COP, and APACHE II scores. Moreover, the serum legumain concentration on admission was elevated in CAP patients who underwent mechanical ventilation, vasoactive agent therapy, ICU admission, and who died during hospitalization. CAP patients with higher serum legumain expression had poor prognostic outcomes. The predictive value of the serum legumain concentration for prognosis was similar to that of the severity score. Conclusions: Serum legumain concentration is positively related to disease severity and a poor prognosis, indicating that serum legumain can be used as an indicator of disease severity and a prognostic indicator for CAP patients.

Keywords: Community-acquired pneumonia; Legumain; Prognosis; Serum biomarker; Severity.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interest exists.

Figures

Figure 1
Figure 1
Comparison of the serum legumain concentration in CAP patients with various disease severities. The expression of legumain in serum samples was determined via ELISA. Differences in the serum legumain concentration were compared among CAP patients with different severity scores. (A) CURB-65. (B) PSI. (C) SMART-COP. (D) APACHE II score. *P<0.05, **P<0.01.
Figure 2
Figure 2
Relationships of serum legumain with clinical indicators in CAP patients. The correlations between the serum legumain concentration and clinical indicators were estimated through the Spearman rank correlation coefficient. (A) Correlation between serum legumain and systolic blood pressure. (B) Correlation between the serum legumain concentration and platelet count. (C) Correlation between serum legumain and urea nitrogen. (D) Correlation between serum legumain and creatinine. (E) Correlation between serum legumain and myoglobin. (F) Correlation between the serum legumain concentration and D-dimer level. (G) Correlation between the serum legumain level and the procalcitonin level. (H) Correlation between the serum legumain concentration and the CRP level. (I) Correlation between serum legumain and IL-6. The R values represent the correlation coefficient.
Figure 3
Figure 3
Comparison of the serum legumain concentration in CAP patients with various prognoses. The expression of serum legumain was determined using ELISA. Differences in the serum legumain concentration were compared in subjects with different prognoses. (A) Mechanical ventilation. (B) Vasoactive agent. (C) ICU admission. (D) Death. **P<0.01.
Figure 4
Figure 4
The predictive power for various prognoses in CAP patients. The predictabilities of various prognostic outcomes were assessed via receiver operating characteristic (ROC) curves. (A) Mechanical ventilation. (B) Vasoactive agent. (C) ICU admission. (D) Death.
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