ALDH1A1 and non-small cell lung carcinoma: We found ALDH1A1 serum levels above a sensitivity threshold of 10 ng/ml (reflecting the estimated background noise) in only three of 45 NSCLC patients (6.7%), while all other NSCLC patients showed ALDH1A1 serum levels comparable with the control cohorts (Figures 4(a) and 4(b)).