SFTPD and chronic obstructive pulmonary disease: There was a statistically significant difference between the exacerbation and stable periods of COPD in terms of median serum SP-D, CRP, WBC (White Blood Cell), neutrophil, eosinophil, pCO2 (partial carbon dioxide pressure), and pO2 (partial oxygen pressure) values (P < 0.05), which are summarized in Table 2.