OBJECTIVES

Provide evidence to support the Asthma Daytime Symptom Diary (ADSD) and the Asthma Nighttime Symptom Diary (ANSD) to measure change in asthma symptom severity in clinical trials.

METHODS

The study was used to assess item performance, factor structure, reliability, construct validity, and sensitivity to change. ADSD was completed each evening; ANSD was completed seven consecutive days at beginning, middle and end of trial. Meaningful change estimates were derived using anchor- and distribution-based approaches.

RESULTS

ADSD (n=428) and ANSD (n=309) study populations were mean ages 52.1 and 51.4 years; predominantly female (n=321, 66.6% and n=201, 65.05%); and white (n=405, 84.02% and n=247, 79.94%). Both six-item measures showed high internal consistency (Cronbach’s alpha coefficients = 0.95 and 0.96); ADSD score reproducibility was observed among subjects stable on PGI-S between baseline and week 26 (ICC = 0.89). Similar ANSD data were insufficient to present ICC. Factor analyses produced high factor loadings (>0.78) for all constituent items supporting overall latent traits of daytime and nighttime symptom severity. As hypothesized, correlations (Spearman’s) of greater magnitude were observed with disease-proximal measures, ACQ-5 and AQLQ symptoms (0.50 and -0.47 and 0.48 and -0.49), than distal measures, AQLQ activity limitations and EQ-5D-5L VAS (-0.39 and -0.36 and -0.43 and -0.39). ADSD and ANSD scores were significantly lower (all p<0.0001) among subgroups categorized on an external anchor as healthier (lower PGIS-PM global symptom severity, better ACQ-5 asthma control, and higher HRQOL based on EQ-5D-5L VAS). Triangulation of anchor- and distribution-based methods supports a 2-point threshold for interpreting meaningful change for ADSD and ANSD.

CONCLUSIONS

Evidence supporting psychometric properties and meaningful change scores are presented for ANSD and ADSD, although additional data to confirm ANSD reliability are warranted.