Analytical and clinical performance of the nanopia krebs von den lungen 6 assay in Korean patients with interstitial lung diseases

Background: Krebs von den Lungen 6 (KL-6) is a sensitive marker for diagnosing, monitoring, and predicting the prognoses of interstitial lung diseases (ILDs). This study aimed to evaluate the performance of the Nanopia KL-6 assay (Sekisui Medical, Tokyo, Japan) and to test the relationship between KL-6 concentrations and clinical results. Methods: In total, 230 patients diagnosed as having ILDs were enrolled. All underwent high-resolution computed tomography (HRCT) followed by the pulmonary function test (PFT). We also enrolled 116 disease controls and 200 healthy controls. Evaluation of the Nanopia KL-6 assay involved determination of precision, linearity, and limit of quantification (LOQ). Results from the Nanopia KL-6 assay were compared with those from ELISA and correlated with the HRCT and PFT results. Results: The within-laboratory precisions were <2% of CV, and linearity was acceptable between 52.2 and 4,966.5 U/mL. The LOQ was 45.2 U/mL. Nanopia and ELISA results were strongly correlated (r=0.979). The average concentration of KL-6 was greater in ILD patients (711.5 U/mL) than in the disease (168.4 U/mL) and healthy (209.4 U/mL) controls. Serum KL-6 concentrations were strongly and moderately correlated with the extent of lung involvement and presence of typical HRCT abnormalities, respectively, and moder-ately correlated with PFT parameters. Conclusions: The overall analytical and clinical performance of the Nanopia KL-6 assay was acceptable. Our study is the first to compare assay platforms and show correlations between KL-6 concentrations and HRCT or PFT results in Korean ILD patients.