Pain is frequently the primary variable in symptomatic clinical trials for the evaluation of rheumatological disorders. The protocol of such trials mention a minimum level of pain as an entry criterion [e.g. a level above the Patient Acceptable Symptoms State (PASS)] and the changes in pain as the primary variable. Usually, the results are expressed at a group level as the mean changes in pain. However, the presentation at an individual level and, in particular, the percentage of patients with a Low Disease Activity State at the end of the study seems more clinically relevant. Pain is usually evaluated using a continuous variable such as a 0-100 visual analogue scale. The cut-offs permitting one to define both the entry criterion and the LDAS are not well established. The objective of this study was to evaluate such cut-offs using a patient-derived perspective.
cross-sectional study.
consecutive out patients suffering from chronic rheumatic diseases familiar with the use of a VAS to evaluate their level of pain.
two questions were asked the patients at the end of the visit: "Based on the experience you have because of your chronic rheumatic disorder, could you please specify the level of pain below which you consider your disease as inactive ? Moreover, could you please also specify the level of pain above which you consider taking a pain killer?" Before answering the second question, it was explained to the patient that their answer to the second question could be similar to their response to the first one. For the two questions, the cumulative percentage of patients (disease inactive and pain killer intake) were calculated for each level of pain.
The underlying disease of the 137 evaluated patients (mean age: 57+/-16 and female sex: 76%) was rheumatoid arthritis (n = 59), ankylosing spondylitis (n = 19), SLE (n = 2), back pain (n = 20), or peripheral osteoarthritis (n = 37). The mean disease duration was 12+/-10 years. At the time of the study, the current level of pain evaluated on a 0-100 VAS was 33+/-22. The LDAS was 49, 36 and 25 for our patient population at the 25th, 50th and 75th percentiles, respectively. The pain killer intake level was 32, 48, 64 at the 25th, 50th, 75th percentile respectively.
This study suggests that LDAS and PASS may be distinct concepts. The methodological approach adopted here could be of interest for specifying the minimum level of symptoms at entry in a symptomatic trial (PASS) and also to present results in terms of the percentage of patients in good condition (LDAS) at the end of a trial.