Rationale: Spirometry is essential in the diagnosis of airway disease and can be useful in monitoring patients. Despite the essential role, spirometry remains largely underused in primary care. Due to Coronavirus disease (COVID-19), the use of office spirometry is contraindicated in many countries. Furthermore, spirometric devices are costly and personnel requires special training. Referral for spirometry increases the cost for patients and lowers the feasibility. Part of the reason for underdiagnosis of airway disease are the specific situations (such as exercise-induced asthma) in which spirometry in office setting might not reveal abnormalities. In recent years, handheld spirometry linked to phones/apps has been developed for study purposes and remote monitoring.

Objective: To study the feasibility, quality and added value of at-home spirometry for the diagnosis and monitoring of asthma and Chronic Obstructive Pulmonary Disease (COPD) in primary care.

Inclusion Criteria:

• Age ≥ 16 years
• Spirometry indication
• Able and willing to use at-home spirometry

Exclusion Criteria:

• On the discretion of the recruiting clinician if he or she deems a patient not eligible.
• Inability to understand and sign the informed consent form
• Known previous inability to perform spirometry
• Contraindications to perform spirometry as listed in the standardization of Spirometry 2019 update (Graham et al., 2019)

In principle, all patients with a spirometry indication diagnosis or monitoring of their airway disease of 16 years or older will be eligible for at-home spirometry.