Serum surfactant protein-A, but not surfactant protein-D or KL-6, can predict preclinical lung damage induced by smoking

Biomarkers. 2008 Jun;13(4):385-92. doi: 10.1080/13547500801903651.


Serum surfactant protein (SP)-A offers a useful clinical marker for interstitial lung disease (ILD). However, SP-A is occasionally elevated in non-ILD pulmonary patients. The present study was conducted to investigate factors that affect serum SP- A levels in respiratory medicine. Serum SP-A, serum SP-D, serum Klebs von den Lungen (KL)-6 and pulmonary function tests were evaluated in 929 patients (current smokers, n=255; ex-smokers, n=242; never-smokers, n=432) without ILD or pulmonary alveolar proteinosis. Serum SP-A was significantly higher in current smokers than in never- or ex-smokers (p<0.01 and p<0.05, respectively). Serum SP- A was significantly higher in chronic obstructive pulmonary disease (COPD) and pulmonary thromboembolism than in other diseases (p<0.01). Serum SP-A correlated positively with amount of smoking (p<0.01) and negatively with forced expiratory volume in 1 s/forced vital capacity (p<0.05). Serum SP-D and KL-6 were unaffected by smoking. Smoking should be taken into account when evaluating serum SP-A levels, and different baseline levels of serum SP-A should be established for smokers and non-smokers. Serum SP-A may also represent a useful marker for predicting COPD in the preclinical stage.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Biomarkers / blood
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Lung / metabolism
  • Lung / pathology*
  • Lung / physiopathology
  • Lung Diseases / blood
  • Male
  • Middle Aged
  • Mucin-1 / blood*
  • Pulmonary Disease, Chronic Obstructive / blood
  • Pulmonary Surfactant-Associated Protein A / blood*
  • Pulmonary Surfactant-Associated Protein D / blood*
  • Respiratory Function Tests
  • Smoking / blood*
  • Smoking / pathology
  • Smoking Cessation


  • Biomarkers
  • MUC1 protein, human
  • Mucin-1
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Protein D