Patient-perceived satisfactory improvement (PPSI): interpreting meaningful change in pain from the patient's perspective.

The assessment of clinically meaningful changes in patient-reported pain has become increasingly important when interpreting results of clinical studies. However, proposed response criteria, such as the minimal clinically important difference, do not correspond with the growing need for information on truly meaningful, individual improvements. The aim of the present study was to investigate satisfactory improvements in pain from the patient's perspective. Data were collected in a 2-week prospective study of 181 arthritis patients treated with a local corticosteroid injection. Baseline and follow-up pain were assessed on 100mm visual analogue scales for pain intensity (VAS-PI). At baseline, patients also marked a hypothetical level on a VAS-PI representing a satisfactory improvement in pain. Patient-perceived satisfactory improvement (PPSI) was constructed using a 5-point categorical rating of change scale at follow-up as the anchor. PPSI was associated with a minimal reduction of 30mm or 55% on the VAS-PI. Since absolute change in pain associated with satisfactory improvement proved highly dependent on baseline pain, percent change scores performed better in classifying improved patients. The 55% threshold for satisfactory improvement was consistent over the course of treatment and reasonably consistent across groups of patients. Our data suggest that PPSI is a clinically relevant and stable concept for interpreting truly meaningful improvements in pain from the individual perspective.