SP-D as a biomarker for COPD in the Lebanese population

Abstract

Background: Surfactant protein D (SP-D), a promising systemic biomarker of chronic obstructive pulmonary disease (COPD) was never evaluated in the Lebanese population.

Objective: The validity of serum SP-D as a biomarker for COPD, in comparison with C-reactive protein (CRP) and fibrinogen was investigated. Associations between SP-D levels and lung function tests and the value of combining SP-D and the Diagnosis Score of COPD (DS-COPD) for COPD diagnosis were also evaluated.

Methods:90 COPD patients and 452 controls were recruited. Standardized questionnaires, lung function tests, COPD diagnosis (GOLD 2013), and blood collection were performed. Serum SP-D and CRP, and plasma fibrinogen levels were measured by ELISA. Associations between biological markers with lung function parameters and COPD were estimated by spearman correlation and logistic regression models respectively.

Results: Median serum SP-D levels for COPD patients were 1510 ng/mL (from 986 to 2174 ng/mL). SP-D levels were positively associated with age and pack-years in controls (all p<0.01). SP-D levels above the median value were positively associated with COPD (adjusted OR (aOR)=2.86, 95%CI: 1.37-5.98). Higher DS-COPD values (aOR=1.8, 1.49-2.16) and SP-D levels above the median value (aOR=3.51, 1.21-10.1) were significantly and independently associated with COPD in patients and healthy controls aged 40 years or above. No associations were found between CRP, fibrinogen levels and COPD, or between SP-D levels and lung function tests.

Conclusion: SP-D seems to be a more reliable biomarker than CRP or fibrinogen for COPD diagnosis in the Lebanese population. Used with the DSCOPD, the SP-D measure could provide a simple and inexpensive tool for COPD diagnosis.