Problems with measurement of the minimum clinically significant difference in acute pain in elders. Bijur Polly E,Chang Andrew K,Esses David,Gallagher E John Academic emergency medicine : official journal of the Society for Academic Emergency Medicine OBJECTIVES:A standard value for the minimum clinically significant difference (MCSD) in pain in nonelderly ED patients has been identified and has facilitated research in this age group. It is not clear that this value is similar in older patients. The standard method for calculating the MCSD in pain is to average scores on a numerical rating scale (NRS) over contiguous time periods. This method is based on the assumption that the MCSD remains constant over time. In an earlier hypothesis-generating study of elderly patients, this assumption was not met for the arithmetic MCSD, making it difficult to identify a single benchmark for measuring efficacy in analgesia trials in elders. The proportional MCSD was more stable, suggesting that it might constitute a better measure of analgesic efficacy in elderly patients. The objective of the study was to test the hypotheses that: 1) the arithmetic MCSD in adults 65 years and older declines over time and that 2) the proportional MCSD remains constant. METHODS:This was an observational, prospective, cohort study of emergency department (ED) patients ≥65 years with acute pain. Pain intensity was rated on a standard 11-point NRS upon study entry and every 30 minutes for 2 hours. The arithmetic MCSD was defined as the mean change in pain between contiguous 30-minute intervals when change in pain was described as "a little less" or "a little more." The proportional MCSD was calculated as the arithmetic MCSD divided by pain intensity at the beginning of the interval. We used generalized estimating equations (GEEs) to test trend over time. RESULTS:A total of 214 patients were enrolled: mean (± standard deviation [SD]) age was 74 (±7.5) years, 66% were female, 63% were Hispanic, and 23% were African American. The median initial NRS was 8. The MCSD decreased 2.1 NRS units (95% confidence interval [CI] = 1.7 to 2.4) between 0 and 30 minutes, 1.4 units (95% CI = 1.0 to 1.7) between 30 and 60 minutes, 1.3 units (95% CI = 1.0 to 1.5) between 60 and 90 minutes, and 0.8 units (95% CI = 0.6 to 1.0) between 90 and 120 minutes (p < 0.001 for trend). The proportional MCSD also varied from 27% (95% CI = 23% to 32%) between 0 and 30 minutes, 19% (95% CI = 13% to 24%) between 30 and 60 minutes, 22% (95% CI = 18% to 27%) between 60 and 90 minutes, and 13% (95% CI = 9% to 18%) between 90 and 120 minutes (p < 0.001 for trend). CONCLUSIONS:Both the arithmetic and the proportional MCSD in elderly patients in acute pain declined over time. Because both measures were numerically unstable, there does not appear to be a single value for the MCSD that can be used to identify the MCSD in pain for use in analgesic efficacy trials in elderly patients. A different metric may be needed to study pain and assess comparative analgesic efficacy in elderly patients. 10.1111/j.1553-2712.2010.00988.x

Clinical importance of changes in chronic pain intensity measured on an 11-point numerical pain rating scale. Farrar John T,Young James P,LaMoreaux Linda,Werth John L,Poole Michael R Pain Pain intensity is frequently measured on an 11-point pain intensity numerical rating scale (PI-NRS), where 0=no pain and 10=worst possible pain. However, it is difficult to interpret the clinical importance of changes from baseline on this scale (such as a 1- or 2-point change). To date, there are no data driven estimates for clinically important differences in pain intensity scales used for chronic pain studies. We have estimated a clinically important difference on this scale by relating it to global assessments of change in multiple studies of chronic pain. Data on 2724 subjects from 10 recently completed placebo-controlled clinical trials of pregabalin in diabetic neuropathy, postherpetic neuralgia, chronic low back pain, fibromyalgia, and osteoarthritis were used. The studies had similar designs and measurement instruments, including the PI-NRS, collected in a daily diary, and the standard seven-point patient global impression of change (PGIC), collected at the endpoint. The changes in the PI-NRS from baseline to the endpoint were compared to the PGIC for each subject. Categories of "much improved" and "very much improved" were used as determinants of a clinically important difference and the relationship to the PI-NRS was explored using graphs, box plots, and sensitivity/specificity analyses. A consistent relationship between the change in PI-NRS and the PGIC was demonstrated regardless of study, disease type, age, sex, study result, or treatment group. On average, a reduction of approximately two points or a reduction of approximately 30% in the PI-NRS represented a clinically important difference. The relationship between percent change and the PGIC was also consistent regardless of baseline pain, while higher baseline scores required larger raw changes to represent a clinically important difference. The application of these results to future studies may provide a standard definition of clinically important improvement in clinical trials of chronic pain therapies. Use of a standard outcome across chronic pain studies would greatly enhance the comparability, validity, and clinical applicability of these studies. 10.1016/S0304-3959(01)00349-9

Minimum detectable and minimal clinically important changes for pain in patients with nonspecific neck pain. Kovacs Francisco M,Abraira Víctor,Royuela Ana,Corcoll Josep,Alegre Luis,Tomás Miquel,Mir María Antonia,Cano Alejandra,Muriel Alfonso,Zamora Javier,Del Real María Teresa Gil,Gestoso Mario,Mufraggi Nicole, BMC musculoskeletal disorders BACKGROUND:The minimal detectable change (MDC) and the minimal clinically important changes (MCIC) have been explored for nonspecific low back pain patients and are similar across different cultural settings. No data on MDC and MCIC for pain severity are available for neck pain patients. The objectives of this study were to estimate MDC and MCIC for pain severity in subacute and chronic neck pain (NP) patients, to assess if MDC and MCIC values are influenced by baseline values and to explore if they are different in the subset of patients reporting referred pain, and in subacute versus chronic patients. METHODS:Subacute and chronic patients treated in routine clinical practice of the Spanish National Health Service for neck pain, with or without pain referred to the arm, and a pain severity > or = 3 points on a pain intensity number rating scale (PI-NRS), were included in this study. Patients' own "global perceived effect" over a 3 month period was used as the external criterion. The minimal detectable change (MDC) was estimated by means of the standard error of measurement in patients who self-assess as unchanged. MCIC were estimated by the mean value of change score in patients who self-assess as improved (mean change score, MCS), and by the optimal cutoff point in receiver operating characteristics curves (ROC). The effect on MDC and MCIC of initial scores, duration of pain, and existence of referred pain were assessed. RESULTS:658 patients were included, 487 of them with referred pain. MDC was 4.0 PI-NRS points for neck pain in the entire sample, 4.2 for neck pain in patients who also had referred pain, and 6.2 for referred pain. MCS was 4.1 and ROC was 1.5 for referred and for neck pain, both in the entire sample and in patients who also complained of referred pain. ROC was lower (0.5 PI-NRS points) for subacute than for chronic patients (1.5 points). MCS was higher for patients with more intense baseline pain, ranging from 2.4 to 4.9 PI-NRS for neck pain and from 2.4 to 5.3 for referred pain. CONCLUSION:In general, improvements < or = 1.5 PI-NRS points could be seen as irrelevant. Above that value, the cutoff point for clinical relevance depends on the methods used to estimate MCIC and on the patient's baseline severity of pain. MDC and MCIC values in neck pain patients are similar to those for low back pain and other painful conditions. 10.1186/1471-2474-9-43

Minimal clinically important changes in chronic musculoskeletal pain intensity measured on a numerical rating scale. Salaffi Fausto,Stancati Andrea,Silvestri Carlo Alberto,Ciapetti Alessandro,Grassi Walter European journal of pain (London, England) OBJECTIVES: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. METHODS: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. RESULTS: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). CONCLUSIONS: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. 10.1016/j.ejpain.2003.09.004