The Patient Assessment of Constipation-Symptoms (PAC-SYM) questionnaire is frequently used in clinical trials of constipation.
However, the threshold for reduction in total PAC-SYM score used to define a clinical response on this 0-4 point scale has not undergone formal appraisal, and its relationship with clinical benefit as perceived by patients has not been defined.
Dr Yiannakou and colleagues determined the minimal important difference in PAC-SYM score, and the optimum cut-off value for defining responders.
The minimal important difference was estimated using data from six international phase 3/4, double-blind, randomised controlled trials of prucalopride in patients with chronic constipation, with anchor- and distribution-based approaches.
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|Alimentary Pharmacology & Therapeutics|
The research team selected 5 appropriate patient-reported outcomes as anchors.
In addition, receiver operating characteristics (ROC) curve analyses were used to investigate responder discrimination for each anchor.
Data from 2884 patients were included.
The researchers found that minimal important difference estimates ranged from –0.52 to –0.63 across the 5 anchors.
The team noted that estimates were not affected by study location but were consistently lower for rectal symptoms than for abdominal and stool symptoms.
Distribution-based estimates were considerably lower than anchor-based estimates.
The research team showed that optimum cut-off scores for discriminating responders to be similar to anchor-based minimal important difference estimates.
Dr Yiannakou's team concludes, "Anchor-based methods gave consistent results for the minimal important difference, at approximately –0.6, and this value was close to the ROC-determined optimal cut-off scores for responder discrimination."
"This value could be considered in clinical practice."
"A slightly more conservative threshold could be used in clinical trials to reduce the placebo response rate."