Gastric aspirates are collected from young children suspected of having pulmonary tuberculosis. While gastric aspirate fluid does not often grow Mtb from children with exclusive extrapulmonary TB, gastric aspiration is frequently attempted for children suspected of having TB meningitis because a positive culture result and susceptibility data are so valuable.
Gastric aspirates are used for collection of mycobacterial cultures in young children when sputa cannot be spontaneously expectorated nor induced using hypertonic saline. Historically, only 25 – 50% of children with active TB will have a positive culture, even when three gastric aspirates are collected.
During sleep, the lung’s mucociliary system beats mucous up into the throat. The mucous is swallowed and remains in the stomach until the stomach empties. Therefore, the highest yield specimens are obtained first thing in the morning.
- Ideally, the patient being prepared for an early morning gastric aspirate should sleep for at least six hours without interruption.
- The patient should not eat or drink anything overnight to prevent the stomach from emptying
Traditionally, three gastric aspirates on consecutive mornings are performed for each patient. This is the number that seems to maximize yield. Of note, the first gastric aspirate collection has the very highest yield and should be collected using the best possible technique. The procedure can be conducted during a hospitalization or in the outpatient clinic setting. Collection during hospitalization may have a slightly increased yield, but there are other benefits to outpatient collection including lower cost and improved rapport with the patient and family.