From the qualitative literature review and concept elicitation interviews, eight core asthma symptoms emerged. These were broadly categorized as breathing symptoms (difficulty breathing, shortness of breath, and wheezing), chest symptoms (chest tightness, chest pain, and pressure/weight on chest), and cough symptoms (cough and the presence of mucus/phlegm). Conceptual saturation was achieved and differences in the experience of participants according to socio-demographic or clinical characteristics were not observed. Subsequent testing of the ADSD confirmed participant relevance and understanding.