Asthma is a major public health problem. The main treatments against asthma are delivered to the lung through several dry-powder inhaler such as Turbuhaler ®, Diskus® and the new Ellipta® device. In real life, patient's ability to handle a device is not routinely assessed by their practitioner. We hypothesized that many asthmatics cannot properly prepare and prime their device, which may alter the positive effects observed in clinical trials.