To differentiate between allergic and non-allergic asthma in a patient presenting with wheezing, a combination of clinical history and specific objective tests is used NICE NG245.
Clinical History:
A structured clinical history is essential NICE NG245. Key aspects to check include:
- Any triggers that worsen symptoms NICE NG245.
- A personal or family history of asthma or allergic rhinitis NICE NG245.
Objective Tests:
If asthma is suspected but not confirmed by initial objective tests such as fractional exhaled nitric oxide (FeNO), bronchodilator reversibility (BDR), or peak expiratory flow (PEF) variability, further investigations for allergic sensitisation should be performed NICE NG245. These include:
- Skin prick testing: Specifically, testing for sensitisation to house dust mite is recommended NICE NG245.
- Blood tests: Measure total IgE level and blood eosinophil count NICE NG245.
A diagnosis of asthma can be made if there is evidence of sensitisation (for example, to house dust mite on skin prick testing) or a raised total IgE level, in conjunction with an eosinophil count greater than 0.5 x 10^9 per litre NICE NG245. Conversely, asthma can be excluded if there is no evidence of sensitisation to house dust mite on skin prick testing or if the total serum IgE is not raised NICE NG245.