PURPOSE: Type 2 pneumocytes and respiratory bronchiolar epithelial cells express a glycoprotein named KL-6 on their surfaces. Small amount of KL-6 is normally found in human serum. Various interstitial lung diseases cause significant elevations in serum levels of KL-6. In addition, in a cross-sectional study, we had previously shown that the mean KL-6 level in lung transplant recipients with bronchiolitis obliterans syndrome (BOS) was significantly higher than that of patients without BOS (689±225.8 U/mL vs. 321±163 U/mL, respectively, p<0.05) and had concluded that measurement of serum KL-6 had the potential to be a non-invasive diagnostic test for BOS. Significant amount of variation found within each group led us to further assess the validity of serum KL-6 measurement as a clinically useful diagnostic test for this purpose. We hypothesized that in lung transplant recipients, significant elevations in serum KL-6 levels would occur during or before stage-1 BOS is diagnosed.
METHODS: We followed KL-6 levels and lung function prospectively in a cohort of lung transplant recipients who were within the first 5 years post-transplant and had no evidence of BOS at the time of study entry. Serum KL-6 levels were determined by using a commercially available ELISA kit. We described a significant rise in serum KL-6 level to be 250 U/mL or more increase from the post-transplant nadir.
RESULTS: There were 36 patients recruited, 5 of whom have developed BOS during the study period. A significant rise in serum KL-6 occurred in 4 out of 5 patients who developed BOS, and 1 out of 31 patients who did not develop BOS, giving a positive predictive value of 80% and a negative predictive value of 97%.
CONCLUSION: Our results indicate that an elevation of 250 U/mL in serum KL-6 level from the post-transplant nadir can detect BOS early and accurately.
CLINICAL IMPLICATIONS: Following serial KL-6 levels after lung transplantation may be a useful, non-invasive screening test for BOS. Longer follow-up of our cohort is required to expand on our findings.
DISCLOSURE: Minh Doan, None.