Asthma daytime and nighttime symptom diaries: content validity and qualitative exploration of meaningful change in patients with moderate-to-severe asthma.

BACKGROUND: Asthma symptom severity can be assessed using the Asthma Daytime and Nighttime Symptom Diaries (ADSD and ANSD), which provide an accurate and standardized patient-reported option for symptom assessment during different periods of the day (i.e. daytime and nighttime), as these can vary significantly. Earlier development and validation work for the ADSD and ANSD was conducted in a broad (i.e. ranging from mild to severe) asthma population, and a US Food and Drug Administration qualification statement noted the need for further evaluation of their measurement properties, including content validity. The current study, which builds upon earlier work, was designed to ensure that the ADSD and ANSD are content-valid in patients with moderate-to-severe asthma.

METHODOLOGY: Qualitative semi-structured concept elicitation and cognitive debriefing interviews were conducted in adults with moderate-to-severe asthma to investigate understanding of ADSD and ANSD instructions, items, recall period, response options, and concept relevance. Changes in total and item scores that were meaningful to patients were explored. General feedback on the measures was also requested.

RESULTS: The study recruited 15 patients with moderate-to-severe asthma. Content validity findings were consistent with previous studies, supporting inclusion of six core symptoms (i.e. wheezing, cough, difficulty breathing, shortness of breath, chest tightness and chest pain) as items in the ADSD and ANSD that occur during a typical day or night and impact upon patient well-being and functioning. A high level of understanding and relevance of the diary items to patients was demonstrated; instructions were confirmed to be easy to follow. In supportive analyses, meaningful levels of improvement on the ADSD and ANSD ranged from 0.5 to 3.5 and 0.2 to 5.0 respectively. Meanwhile, meaningful levels of worsening on the ADSD and ANSD ranged from 1.0 to 5.8 and 0.5 to 6.7 respectively.

CONCLUSIONS: The ADSD and ANSD are content-valid measures for the measurement of daytime and nighttime symptoms and their severity in patients with moderate-to-severe asthma. Additional confirmatory studies are required to confirm the psychometric properties of the ADSD and ANSD in a moderate-to-severe population and to quantitatively estimate the threshold for meaningful improvement and worsening.