Laboratory Tests

Doctors may order one or more kinds of laboratory tests to help determine if a person has lung cancer.

Blood tests

Blood tests do not diagnose lung cancer, but they provide a doctor information on a patient’s overall health and information on how well the organs of the body are functioning.

A complete blood count (CBC) is ordered to check for:

  • Anemia, a low number of red blood cells
  • Thrombocytopenia, a low number of platelets, which can cause bleeding
  • Neutropenia, a low number of white blood cells (WBCs), which can put a patient at increased risk for infection

Blood chemistry tests are used to check whether a patient’s liver or kidneys are working well. The results from these blood tests help the doctor decide if a patient is able to undergo surgery or receive another type of lung cancer treatment.

Sputum cytology

If lung cancer is suspected, sputum cytology may be performed. The patient may be asked to cough up phlegm so a pathologist can look at it under a microscope. A doctor usually orders a patient to provide phlegm three mornings in a row. A pathologist can locate cancer cells in the mucus, but most of the time there are not enough cells to make a final diagnosis of lung cancer.

Sputum cytology is more likely to help diagnose lung cancers that start in the major airways of the lung, such as most squamous cell lung cancers. It may not be as helpful for finding other types of lung cancers. It also does not provide information on how far the disease has spread, so if it is positive for lung cancer other diagnostic tests must be performed.1

Updated February 26, 2016


  1. “Lung Cancer – Non-Small Cell: Diagnosis. American Society of Clinical Oncology website. Approved August 2015. Accessed February 26, 2016.