The
minimal clinically important change for the PAS-II (Patient Activity Scale-II)
is defined as a change in the score of 0.5 units.
In a study, it was demonstrated that the MIC (minimal important change) for PAS-II was approximately 0.5. Among participants with moderate to high PAS-II, the MCII was 1.1. Among participants with low disease activity, the MCIW was found to be 1.1.
This large patient registry aimed to define the
MCII (Minimal Clinically Important Improvement) and MCIW (Minimal Clinically
Important Worsening) for the PAS-II (range 0-10), a recommended well-validated
patient-reported outcome measuring the activity of rheumatoid arthritis
disease.
Data from Forward, The National Databank for Rheumatic Diseases from
four 6-month data
collection periods were used. To estimate MCII and MCIW, both anchor-based and distribution-based methods were used. Anchor-based analyses used comparisons of pain and general health compared to six months ago. Distribution-based analyses used 0.5 and 0.35 SD (standard deviations).
The analyses were stratified based on the
PAS-II score (above/below 3.7). It was hypothesized that the MCII and MCIW
would depend on the baseline score. To determine construct validity, the odds
of achieving the MCII in patients receiving novel therapies were examined.
In the overall sample, the MCIW was 0.50 and
0.55 for pain and general health-related questions respectively. The MCII was
defined as 0.39 to 0.45, respectively as shown in Table 1:
Among patients with low disease activity (PASII3.7), the MCIW for pain and health-related anchor questions were 1.09 and 1.11, respectively. Among patients with high disease activity (PAS-II >3.7), the MCII for pain and health-related anchor questions were 1.15 and 1.02, respectively as shown in Table 2:
Distribution-based methods resulted in a minimal clinically important change of 1.08 and 0.76, for 0.5 SD and 0.35 SD respectively as depicted in Table 3:
A fair to
excellent agreement with clinically significant differences in assessments of
pain and disability was witnessed. Patients initiating new treatments for RA
had 30% greater odds of attaining the MCII. Thus, the characterization of
clinically meaningful changes in disease activity is crucial for clinical
research studies and clinical settings where this disease assessment is
utilized.
Arthritis Care Res [Hoboken]
Defining Minimally Important Changes for the Patient Activity Scale-II
Joshua F. Baker et al.
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