Asthma Tests

Exercise tests

These are widely used in the diagnosis of asthma in children. Ideally, the child should run for 6 minutes on a treadmill at a workload which is sufficient to increase their heart rate above 160 beats per minute. Alternative methods use cold air challenge.

Histamine

This test indicates the presence of airway hyper responsiveness, which is a feature found in most asthmatics. It can be predominantly useful in investigating those people whose main symptom is a cough.

Trial of corticosteroids

All asthma sufferers presenting with a severe airflow restriction should undergo formal trials of steroids. Prednisolone 30 mg orally is usually given daily for 2 weeks with their lung function measured before and immediately after the course. A significant improvement confirms the benefits of this type of treatment for the asthma sufferer. If the trial is for 2 weeks or less, the oral steroids can be withdrawn without tailing off the dose, and should be replaced by inhaled corticosteroids in those people who have responded and are thought will benefit from this medication. Blood and sputum tests.

Individuals with asthma often have an increase in the number of eosinophils in peripheral blood. However the presence of large numbers of eosinophils in the sputum is a more useful diagnostic tool.

Chest X-ray

This has a slightly limited use as there are no diagnostic features of asthma on a chest X-ray, although during an acute occurrence or in chronic severe disease over inflation is a characteristic often found in a chest x-ray.

Skin tests

Skin-prick tests should be performed in all cases of asthma to help identify allergic triggers .