TB & mycobacteria / Test explainer
How to collect a sputum sample for TB testing
Three early morning samples, done properly, with the practical detail that decides whether the test works.
How to collect a sputum sample for a TB test
What the test is for
We are testing your phlegm for a group of bacteria that includes the one that
causes tuberculosis, and for related bacteria called non-tuberculous
mycobacteria. These related bacteria live in soil and water and are usually
harmless, but they can settle in lungs that are already damaged.
What we need
Three separate samples, collected on three different days, at least 24 hours
apart. First thing in the morning is best, because phlegm collects in the
lungs overnight and the morning sample is the one most likely to give an
answer.
We have given you three pots with labels that have your details on them, and a
bag for each.
How to collect a good sample
1. Do not open the pot until you are ready to use it. It is sterile inside.
2. As soon as you wake up, before you eat or drink anything, brush your teeth
and rinse your mouth with water. Do not use mouthwash - it can kill the
bacteria we are trying to grow.
3. Take three deep breaths in through your nose, breathing out slowly through
pursed lips each time.
4. After the third breath, cough deeply from your chest and spit what comes up
into the pot.
5. What we need is phlegm from your lungs, not saliva from your mouth. Saliva
cannot be tested. It usually takes a few good coughs, and it may take a couple
of minutes.
6. Screw the lid on firmly so it cannot leak. Write the date on the pot and put
it in its bag.
Storing and returning the samples
If you can bring each sample in on the day you produce it, that is best.
Otherwise, keep the pot in the fridge, in its bag, away from food, and bring it
in as soon as you can. Do not keep samples at home for more than three days.
Bring them to [] .
Practical points
Try not to start on a Thursday or Friday, because the third day then falls at
the weekend.
If you cannot produce phlegm three days running, bring in two, or even one. One
good sample is far better than none.
If you cannot cough anything up at all, contact us. There are other ways of
getting a sample, including a saline mist that helps bring phlegm up, and we
can arrange this.
Tell other people in your household not to open the pots, and keep them out of
reach of children.
Your results
Some results are available within a few days. Growing these bacteria in the
laboratory is slow, and a final result can take up to eight weeks. We will
contact you with the results, and we will not wait for the final culture before
starting treatment if you need it sooner.
Thank you - this is a test where the care you take with the sample really does
decide whether it gives us an answer.
How to use it
The yield of mycobacterial culture depends almost entirely on sample quality, which is decided by the patient in their bathroom rather than by anyone in the hospital, so the instructions are worth giving properly. The mouthwash warning and the saliva-versus-sputum distinction are the two errors that most often produce an uninterpretable sample. Angshu's Thursday-and-Friday note is kept because it is the kind of thing only someone who has run the clinic for years would think to write down. The eight-week culture time is stated up front to prevent a fortnight of anxious phone calls.
Why it says that
None of this is in the copied text. It is here so you can check the block against its source, and change it when the source changes.
- NICE NG33 - Tuberculosis Send multiple respiratory samples, including at least one early morning sample, for smear and culture before starting treatment where possible.
- WHO consolidated guidelines on tuberculosis: diagnosis Specimen quality and handling, and the role of rapid molecular testing alongside culture.
- BTS guideline for the management of non-tuberculous mycobacterial pulmonary disease Diagnosis requires two separate positive sputum cultures, which is why three samples are collected rather than one.