The Symptom Free Days Questionnaire (SFDQ) for patients with asthma was an unsuccessful data collection method in the Blacks and Exacerbations on Long-Acting Beta Agonists and Tiotropium (BELT; ClinicalTrials.gov Identifier: NCT01290874) clinical trial population, according to results published in the Journal of Asthma.
Researchers pooled 1070 self-identified black adults who had been diagnosed with asthma and had an Asthma Control Questionnaire score >1.25. All participants completed the SFDQ, the Asthma Symptom Utility Index, other related questionnaires, and spirometry at baseline and then completed these again at month 1, month 6, and month 12. Response consistency, specifically number of patient-reported days with symptoms over a 14-day period, was compared with the number of patient-reported days with no symptoms during the same period. Researchers used Lin concordance correlation coefficients (Lin ccc) to calculate demographics and learning.
The internal responses from the 1070 participants were consistently low, varying from 43.8% at baseline to 52.1% at study conclusion. This corresponded to Lin ccc of 0.33 to 0.32 across the study timeline. Internal consistency and the Lin ccc did not differ by age group, sex, location, or income.
“Based on the results from this population of black adults with high rates of inadequately controlled asthma, the SFDQ does not appear to be internally consistent with a Lin ccc considered to represent only fair concordance,” the researchers concluded. They also emphasized that results may differ in other demographic groups but suggested that the SFDQ be reevaluated.
Yawn BP, Israel E, Wechsler M, et al.The asthma Symptom Free Days Questionnaire: how reliable are patient responses? [published online October 26, 2018]. J Asthma. doi:10.1080/02770903.2018.1531990