To determine the minimal clinically important difference (MCID) of changes in chronic musculoskeletal pain intensity that is most closely associated with improvement on the commonly used and validated measure of the patient's global impression of change (PGIC), and to estimate the dependency of the MCID on the baseline pain scores.
This was a prospective cohort study assessing patient's pain intensity by the numerical rating scale (NRS) at baseline and at the 3 month follow-up, and by a PGIC questionnaire. A one unit difference at the lowest end of the PGIC ("slightly better") was used to define MCID as it reflects the minimum and lowest degree of improvement that could be detected. In addition we also calculated the NRS changes best associated with "much better" (two units). In order to characterize the association between specific NRS change scores (raw or percent) and clinically important improvement, the sensitivity and specificity were calculated by the receiver operating characteristic (ROC) method. PGIC was used as an external criterion to distinguish between improved or non-improved patients.
825 patients with chronic musculoskeletal pain (233 with osteoarthritis of the knee, 86 with osteoarthritis of the hip, 133 with osteoarthritis of the hand, 290 with rheumatoid arthritis and 83 with ankylosing spondylitis) were followed up. A consistent relationship between the change in NRS and the PGIC was observed. On average, a reduction of one point or a reduction of 15.0% in the NRS represented a MCID for the patient. A NRS change score of -2.0 and a percent change score of -33.0% were best associated with the concept of "much better" improvement. For this reason these values can be considered as appropriate cut-off points for this measure. The clinically significant changes in pain are non-uniform along the entire NRS. Patients with a high baseline level of pain on the NRS (score of >7 cm), who experienced either a slight improvement or a higher level of response, had absolute raw and percent changes greater that did patients in the lower cohort (score of less than 4 cm).
These results are consistent with the recently published findings generated by different methods and support the use of a "much better" improvement on the pain relief as a clinically important outcome. A further confirmation in other patient populations and different chronic pain syndromes will be needed.
"This variable was chosen to investigate whether an increase of maximal pain during the first weeks was a barrier to continue with the exercise program. The NRS has an excellent ability to detect change and a reduction of 2 points or 30% on NRS scores is considered to be clinically important (Farrar et al., 2001; Hawker et al., 2011; Salaffi et al., 2004). Elderly prefer the NRS above other pain measure instruments (Peters et al., 2007). "
[Show abstract][Hide abstract] ABSTRACT: Background:
Exercise effectiveness is related to adherence, compliance and drop-out. The aim of this study is to investigate if exercise-induced pain and health status are related to these outcomes during two exercise programmes in knee osteoarthritis patients.
Symptomatic knee osteoarthritis patients were randomly allocated to a walking or strengthening programme (N=19/group). At baseline, patients were categorized according to their health status. Exercise adherence and compliance were calculated and drop-out rate was registered. For exercise-induced pain, patients rated their pain on an 11-point numeric rating scale (NRS) before and after each training session. Before each session the maximal perceived pain of the last 24h (NRSmax24) was assessed. Patients rated their global self-perceived effect (GPE) on a 7-point ordinal scale after the intervention period.
53% of the participants felt they improved after the programme, 6 patients dropped out. The mean adherence and compliance rates were higher than .83 in both groups. Worse health and higher exercise-induced pain were seen in drop-outs. NRSmax24 during the first 3weeks did not significantly increase compared to baseline, but correlated negatively with adherence during the home sessions (-.56, p<.05). Lower adherence during supervised sessions was significantly related with higher pre-exercise pain scores (ρ=-.35, p<.05).
Patients who drop-out show a worse health condition and higher exercise-induced pain levels compared to patients that retained the programme.
"The sample size calculation was based on a change of two points on the Numeric Rating Scale (NRS) for pain intensity, determined to be clinically relevant for musculoskeletal pain (Salaffi et al., 2004). Based on this, 20 subjects (ten per group) were required to detect a difference of two NRS points, including a standard deviation of 1.5, a power of 80%, with significance level of 5%. "
"The minimum clinically important difference (MCID) on an NRS in people with chronic musculoskeletal pain is two points (Salaffi et al., 2004). Therefore, c 2 analysis was undertaken to determine whether there was a significant between-group difference for proportions of participants demonstrating change scores of > or < two points, or the degree of change defined by O'Neill et al. (2014). "
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