To examine the value of daily pain measurements in patients with hip osteoarthritis (OA), and whether the reliability of retrospective measurements was lower in patients with intermittent pain than in patients with more constant pain.
We used data from a randomized controlled trial that investigated the effectiveness of general practitioner care plus exercise therapy in 203 patients with hip OA. During the first 6 weeks, patients scored their pain each day. These daily measurements were available for 185 patients. At 6-week follow-up, patients filled in a questionnaire rating their pain during the previous week. We examined whether the daily measurements provided results for pain other than those provided by retrospective measurements, using a linear mixed-effects model. We also explored differences between subgroups, based on the frequency and severity of intermittent pain, during the pain course and reliability between retrospective measurements and daily measurements.
Daily measurements showed no different effect of exercise therapy on pain compared with retrospective measurements. We found statistical differences (by analysis of variance) during the course of pain between the subgroups based on the intensity of intermittent pain. Reliability between retrospective and daily measurements was lower in the subgroup with severe intermittent pain (Cronbach's α = 0.642) than in other subgroups (Cronbach's α >0.843).
In this specific trial, daily measurements did not yield more precise or additional information compared with retrospective measurements at the 6-week follow-up. However, reliability of retrospective measurements may be lower in patients with a higher intensity of intermittent pain.