Asthma affects 8% of the entire population. 4-5% of asthma sufferers have severe asthma, characterised by recurrent exacerbations (worsening of symptoms leading to the person having a bout of corticosteroids and/or antibiotics), significant symptoms and lack of response to the most widely used therapy, corticosteroids.

There is now new types of treatments (antibody drugs) which are licensed to manage severe asthma such as Anti-IL5. There is evidence Anti-IL5 and other similar antibody drugs are effective at reducing asthma exacerbations and reduce the need for oral corticosteroids for those that have severe asthma.

However, some patients respond poorly to Anti-IL5 and the investigators would like to find out why this happens. It is hoped that the investigators can identify the mechanism of poor treatment response to Anti-IL5. It is also hoped that the investigators can understand why symptoms worsen to the point of requiring antibiotics and/or steroids (also known as an exacerbation) for those prescribed Anti-IL5.

Inclusion criteria: case participants:

• Aged 18 - 80 years old
• Able to give informed consent
• All patients identified as being suitable for anti-IL5 therapy by the asthma MDT will be considered for study enrolment.

This assessment by the MDT for participants to be eligible includes:

• A measure of compliance with current asthma medication,
• Confirmation of asthma diagnosis
• Suitability for anti-IL5 therapy based on blood eosinophil counts,
• Asthma exacerbation rates
• Prednisolone dose.
• Confirmation of treatment requires at least two asthma specialists to agree that this is the correct course of action
• Patients must first demonstrate over 75% compliance with inhaled and/or oral corticosteroid therapy

The asthma MDT and difficult asthma clinic normally assess patients between 18-80 years so only patients in this age range will be approached.

All patients will be able to give informed consent for study participation.

Exclusion criteria: case participants:

• Pregnancy

Inclusion criteria: control participants:

• Aged between 18-80 years old.
• Able to give informed consent

Exclusion criteria: control participants:

• Pregnancy
• Underlying respiratory conditions

Participants will be recruited from the severe asthma clinic. Once the multidisciplinary team (MDT) have decided that the patient will be prescribed anti-IL5 therapy a patient information sheet (PIS) will be posted out by the clinical team. If the appointment with the clinical team is within days of the MDT, potential participant will be approached by a member of the research team and the study will be discussed and a patient information sheet will be given to the patient.

Control participants will be recruited from our Respiratory Research Database and have agreed to be contacted for research. A poster will be created to be put up in Nottingham City Hospital, Queen's Medical Centre and at the University of Nottingham, UK.