Predicting Steroid Response Using Exhaled Nitric Oxide

Asthma affects 6% of the UK population and costs the NHS 1 billion pounds per year. £473 million alone is spent on inhaled steroid treatment which is designed to reduce inflammation in the breathing tubes. Unfortunately knowing whether a patient is on just the right amount of steroid treatment is difficult, as asthma is a variable disease and the measures currently used to decide on increasing or decreasing steroid treatment bare little resemblance to the actual amount of inflammation present. Doctors may not reduce treatment as swiftly as necessary if a patient's asthma is well controlled because of concern over asthma attacks; this can result in potential over treatment with inhaled steroids. Although steroid treatment is safe, side effects can occur, and costs are large, so a strategy helping avoid over treatment would be beneficial both to patients and to the NHS. As the investigators can more accurately measure airway inflammation present in the breathing tubes, using a chemical called nitric oxide present in a patient's breath, the investigators might be able to more accurately predict which patients could safely reduce their steroid treatment. Measuring nitric oxide is simple, and involves breathing into a special machine (similar to a roadside breathalyser). In this study the investigators will measure nitric oxide in patients with well controlled asthma, and reduce their asthma treatment by 50%. The investigators will then follow up the patients and remeasure their nitric oxide. At the end of the study the investigators will see if measurements of nitric oxide predicted which patients could safely step down their treatment. If successful this could help reduce the overall cost to the NHS of inhaled steroids and reduce steroid associated side effects.