Table 2 Results of medical examinations
Exposed workersNon-exposed workersp Value
Serum immunochemistryGMGSDGMGSD
    KL-6 (U/ml)495.42.26240.11.44<0.0001
    SP-D (ng/ml)85.22.0251.71.73<0.0001
    SP-A (ng/ml)39.61.5733.81.520.0133
    CRP (mg/dl)
Serum immunochemistry exceeding the reference values
    KL-6 >5003941.922.2<0.0001
    SP-D >1103739.877.5<0.0001
    SP-A >43.84043.12324.70.0081
    CRP >0.377.587.70.8217
Positive HRCT changes
    Interstitial changes66.599.70.4177
    Emphysematous changes77.555.40.5497
Respiratory symptom complaints
    Current smokers
        Cough in winter1015.9612.20.5841
        Cough in all seasons1016.136.10.1402
        Phlegm in winter1219.412250.4784
        Phlegm in all seasons1219.41019.80.8901
    Ex or never smoked
        Cough in winter826.7613.60.1636
        Cough in all seasons723.3511.40.1742
        Phlegm in winter723.336.80.0792
        Phlegm in all seasons516.736.80.2569
  • GM, geometric mean; GSD, geometric standard deviation. Prev, prevalence (%).

  • For test of difference in mean, Student t test or Welch t test (KL-6 and SP-D) was adopted. For test of prevalence, χ2 test or, if number in a cell was 4 or less, Fisher’s exact method was applied.