Longitudinal Preschool Wheeze Biomarker Study

These children who will be having a bronchoscopy (a long thin tube, with a camera at the end, which is put inside the lung to look at and collect samples) as part of their standard clinical management, determined by their own consultants or treating physicians. They will be having lung samples (washings from the lung and a tiny piece of tissue taken from the breathing tubes) taken as part of their usual medical management. The research team will ask for consent to use the leftover samples for the bronchoscopy, for the study

To identify children with allergies. This test will not be done if the child has had allergy testing in the last 6 months

Finger prick testing will be used for blood samples, and it is the same technique used by children with diabetes, to test their blood sugar levels, and therefore is regularly used in this age group successfully. The research team will be obtain the results within minutes, using a point-of-care device. A few more drops of blood, from the same finger prick sample, will be taken to look at how one of the blood cells work, in more detail, in the laboratory. There is no additional finger prick required for this lab test, and the drops of blood will be collected at the same time, from the same prick, as the point of care test.

Breathing test will be performed using forced oscillation technique (FOT), to see how the child's lungs work and to detect airway inflammation. The test will be explained to the child and completed using our established protocols. This test will only require the child to breathe in and out normally, and therefore can be done in preschool aged children. The current test that is used to check lung function called spirometry cannot be used in preschool children, as it involves following complicated instructions. The aim is to assess how well this newer lung function test is tolerated, in children aged 1-5 years.

Sputum induction is a test of obtaining phlegm after inhalation of salt water mist (saline nebuliser) and this will allow the research team to look for any relationships between infection in the lungs and the accuracy of the less invasive, nose and throat swabs. The research team will obtain phlegm samples, with a quick suction after patients have inhaled the salty mist (saline nebuliser) which will help loosen up their phlegm. If the child can cough it up, they will be encouraged to do it.

Swabs from children's nose and throats (similar to swab tests that are done for Covid tests), that will be used to test for bacterial infection