Serum KL-6 Concentrations in Dairy Farmers

Serum KL-6 (Krebs von den Lungen-6) has been recognized to be a marker for the activity of diffuse interstitial lung diseases. The purpose of the study is to evaluate serum KL-6 measurement as a marker for farmer's lung disease (FLD). A cross-sectional survey of a cohort of dairy farmers. Retrospective measurement of KL-6 stored serum samples from those dairy farmers previously screened for FLD. University hospital screening project for FLD within a dairy-farming community in Japan. Four hundred seventy-two dairy farmers were invited to attend a local clinic. We examined serum KL-6 concentrations in 272 farmers. Subjects were classified into three groups: (1) 5 farmers with FLD, (2) 30 farmers with positive serum precipitating antibodies to Saccharopolyspora rectivirgula and/or Thermoactinomyces vulgaris without FLD (Ab+), and (3) 237 farmers without these antibodies (Ab−). Serum KL-6 concentrations in the FLD group were significantly higher than those in the Ab+ and the Ab− groups (1,263 ± 288 [SEM], 328 ± 57, and 207 ± 6 U/mL, respectively, p < 0.001). Serum KL-6 concentrations in those with FLD were significantly higher than KL-6 concentrations from stored screening samples from the same individual when FLD was not diagnosed (1,263 ± 288 and 419 ± 209 U/mL, respectively, p < 0.05). Serum KL-6 concentrations of the Ab+ group were significantly higher than those of the Ab− group (p < 0.001). In the Ab+ group, farmers with high serum KL-6 concentrations had lower permeability coefficients than farmers with normal serum KL-6 concentrations (p < 0.05). These results may suggest that subclinical FLD can be detected in farmers with high KL-6 concentrations and precipitating antibodies. Serum KL-6 concentration can be a useful marker for assessing the activity of FLD and may be able to be used to detect subclinical disease.