From analyses of individual patient data ( seven studies , 918 patients ) , we found baseline pain strongly associated with absolute , but not relative , MCID as patients with higher baseline pain needed larger pain reduction to perceive relief .
Conclusions The MCID in acute pain varied greatly between studies and was influenced by baseline pain , definitions of improved patients and study design .
Background The minimum clinical ly important difference ( MCID ) is used to interpret the clinical relevance of results reported by trials and meta-analyses as well as to plan sample sizes in new studies .
However , there is a lack of consensus about the size of MCID in acute pain , which is a core symptom affecting patients across many clinical conditions .
Problems with measurement of the minimum clinically significant difference in acute pain in elders.
OBJECTIVES A st and ard value for the minimum clinical ly 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 st and ard 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 , prospect i ve , cohort study of emergency department ( ED ) patients ≥65 years with acute pain . Pain intensity was rated on a st and ard 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 ( ± st and ard 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
From analyses of individual patient data ( seven studies , 918 patients ) , we found baseline pain strongly associated with absolute , but not relative , MCID as patients with higher baseline pain needed larger pain reduction to perceive relief .
Conclusions The MCID in acute pain varied greatly between studies and was influenced by baseline pain , definitions of improved patients and study design .
Background The minimum clinical ly important difference ( MCID ) is used to interpret the clinical relevance of results reported by trials and meta-analyses as well as to plan sample sizes in new studies .
However , there is a lack of consensus about the size of MCID in acute pain , which is a core symptom affecting patients across many clinical conditions .