Can lung cancer be detected through a routine blood test?

In general, routine blood tests cannot directly detect lung cancer. A complete blood count (CBC) only reflects changes in indicators such as red blood cells, white blood cells, and platelets, but cannot identify lung cancer cells or confirm the presence of a tumor in the lungs. The specific analysis is as follows:

In the early stages of lung cancer or in some cases of moderately advanced disease, CBC results may be entirely normal. Abnormalities in blood counts typically appear only when complications arise from lung cancer—for example, elevated white blood cell counts due to infection associated with lung cancer, or decreased red blood cells and hemoglobin levels caused by bleeding or malnutrition in advanced lung cancer. However, these abnormalities are not unique to lung cancer; similar results can also occur in other conditions such as pneumonia or anemia, making it impossible to distinguish lung cancer based on CBC alone. Clinically, diagnosing lung cancer relies on imaging studies and pathological examinations, which allow direct observation of lung lesions or confirmation of malignant cellular changes, and are essential for definitive diagnosis.

Therefore, routine blood tests are not suitable for lung cancer screening or diagnosis, but can only assist in identifying complications such as infection or anemia in patients already diagnosed with lung cancer. Individuals experiencing persistent symptoms suggestive of lung cancer—such as long-term cough or hemoptysis—should promptly undergo targeted evaluations like chest CT scans, avoiding delays in diagnosis due to overreliance on routine blood testing.