ALK and non-small cell lung carcinoma: ALK-positive NSCLC patients had a significantly higher mean O.D. level (range 0 to 4031, mean ± SD = 643.4 ± 767.8) compared to ALK-negative NSCLC patients (range 24 to 861, mean ± SD = 346.8 ± 174.9, P = 0.02), as shown in Figure 1.