There are many ways to diagnose lung cancer, and sputum cytology is probably one of the “easiest”.
What is sputum cytology?
What is a sputum cytology test?
What is sputum cytology?
A sputum cytology test is when a pathologist looks at a sample of a patient’s sputum under a microscope and determines whether abnormal cells are present. Unlike saliva, sputum is produced in the lungs and in the bronchi that lead to the lungs and may contain some lung cells, making it valuable for examination.
This test can be used to help confirm the diagnosis of either lung cancer or non-cancerous lung disease (such as pneumonia, tuberculosis, or asbestosis), but keep in mind that sputum testing is not a panacea; just because it doesn’t detect it doesn’t mean it’s not lung cancer, and it’s relatively more meaningful for central lung cancer.
How is the test done?
Sputum samples may come from mucus that the patient coughs up (inhalation of saline mist helps cough up mucus) or may be removed by bronchoscopy.
In the case of bronchoscopy, there are some precautions to follow:
Tell your doctor about these conditions before the examination:
- Which medications are being taken;
- History of drug allergies (including narcotics);
- Whether taking antiplatelet agents (e.g., aspirin, clopidogrel) or anticoagulants (e.g., warfarin)
- Whether pregnant (or possibly pregnant)
The doctor will fully inform you about the purpose of the test, how it will be performed, the risks and how to fast and abstain from food and water before the test, so please follow the doctor’s instructions strictly or the procedure may be cancelled. If you need to take medication on the day of the test, please take it with a small sip of water only.
To take a sample, the doctor will pass a thin bendable tube down the nose or mouth into the throat and into the bronchial tubes that lead to the lungs.
In the case of cough sampling, the physician gives the patient a sampling cup (which may contain some fluid that should not be drunk; it is a fixative to preserve the sample) and needs to collect 3 sputum samples over 3 days. To obtain the most valid results, samples should be collected early in the morning immediately after waking. The steps are as follows:
If wearing dentures, remove them first;
- Rinse your mouth with water;
- Take about 4 deep breaths, cough briefly a few more times, then inhale deeply and forcefully cough up the sputum into the cup. If it feels difficult to get sputum this way, do it again after a hot water bath to loosen the mucus in the airways.
Send the sample as soon as it is taken. If it cannot be submitted right away, it may need to be refrigerated first. In any case, be sure to submit the sample as requested by your doctor. Results are usually available a few days after submission.
What are the advantages of sputum cytology?
Either at home or in the clinic, coughing up a sputum sample is risk-free, convenient and easy to perform, with little or no injury that may be uncomfortable with deep breathing or coughing.
Bronchoscopy is also a safer procedure with fewer complications and the possibility of infections such as bronchospasm, arrhythmias (heart rhythm disorders), and pneumonia.
What are the limitations of sputum cytology?
If the sputum sample is too small, dried up, or contains only saliva or nasal secretions, then the results may not be informative.
Sputum cytology may also give false-negative results, where the test shows no pulmonary disease but in fact it does not. If pulmonary symptoms persist after the test, then the possibility of pulmonary disease needs to continue to be considered.
With the increasing demand for tumor cell specimens for diagnostic treatment, sputum examination has been used relatively sparingly. Currently, bronchoscopy or lung puncture biopsy is the more commonly used test.
Co-reviewed by Dr. Dong Song Dr. Zhang Chao, Guangdong Provincial People’s Hospital, Guangdong Lung Cancer Research Institute, Guangdong Province, China