Establishing Thresholds for Minimal Clinically Important Differences for the Peripheral Artery Disease Questionnaire

Understanding minimum clinically important differences (MCID) in patient-reported outcomes is essential in interpreting the magnitude of changes in these measures. No MCID from patients' perspectives has ever been published for peripheral artery disease-specific health status assessment tools. The Peripheral Artery Questionnaire (PAQ) is a commonly used, validated peripheral artery disease-specific health status instrument for which we sought to prospectively establish its MCID from patients' perspectives.

Patients presenting to vascular clinics with new or worsened claudication in the US cohort of the PORTRAIT (Patient-Centered Outcomes Related to Treatment Practices in Peripheral Arterial Disease: Investigating Trajectories) registry who completed baseline and follow-up PAQ assessments along with the Global Assessment of Functioning scale were included. Mean change in PAQ summary scores from 3- to 6-month follow-up was calculated according to Global Assessment of Functioning category. MCID was defined as the mean difference in scores between those with small improvement or deterioration and those with no change. Multivariable linear regression was used to provide an MCID estimate after adjusting for patients' 3-month PAQ score. Of the 483 patients who completed the Global Assessment of Functioning score at 6 months and who had available 3- and 6-month PAQ assessments, the mean age was 69 years, 42% were female, and 71% were White. The MCIDs for PAQ summary scale improvement and worsening were 8.7 (2.9-14.5) and -11.0 (-18.6 to -3.3), respectively. After multivariable adjustment, these were 8.9 (3.0-14.8) and -11.2 (-18.2 to -4.2), respectively. There was no significant interaction between treatment (invasive versus noninvasive) and Global Assessment of Functioning response (P=0.75).

In patients with new or worsened claudication, a 10-point change in PAQ summary score represents an MCID. This estimate needs external validation and may inform the interpretation of PAQ scores when used as outcomes in clinical trials or in routine clinical care. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01419080.