Application of a High Throughput Method of Biomarker Discovery to Improvement of the <em>Early</em>CDT^®-Lung Test

<div><h3>Background</h3><p>The National Lung Screening Trial showed that CT screening for lung cancer led to a 20% reduction in mortality. However, CT screening has a number of disadvantages including low specificity. A validated autoantibody assay is available commercially (<em>Early</em>CDT®-Lung) to aid in the early detection of lung cancer and risk stratification in patients with pulmonary nodules detected by CT.</p> <p>Recent advances in high throughput (HTP) cloning and expression methods have been developed into a discovery pipeline to identify biomarkers that detect autoantibodies. The aim of this study was to demonstrate the successful clinical application of this strategy to add to the <em>Early</em>CDT-Lung panel in order to improve its sensitivity and specificity (and hence positive predictive value, (PPV)).</p> <h3>Methods and Findings</h3><p>Serum from two matched independent cohorts of lung cancer patients were used (n = 100 and n = 165). Sixty nine proteins were initially screened on an abridged HTP version of the autoantibody ELISA using protein prepared on small scale by a HTP expression and purification screen. Promising leads were produced in shake flask culture and tested on the full assay. These results were analyzed in combination with those from the <em>Early</em>CDT-Lung panel in order to provide a set of re-optimized cut-offs. Five proteins that still displayed cancer/normal differentiation were tested for reproducibility and validation on a second batch of protein and a separate patient cohort. Addition of these proteins resulted in an improvement in the sensitivity and specificity of the test from 38% and 86% to 49% and 93% respectively (PPV improvement from 1 in 16 to 1 in 7).</p> <h3>Conclusion</h3><p>This is a practical example of the value of investing resources to develop a HTP technology. Such technology may lead to improvement in the clinical utility of the <em>Early</em>CDT­-Lung test, and so further aid the early detection of lung cancer.</p>