Pain relief that matters to patients: systematic review of empirical studies assessing the minimum clinically important difference in acute pain

Table 3 Clinically important differences in acute pain

		Analysis of medians^a		Analysis of pooled average
Clinically important difference	Range	Number of studies (patients^b)	MCID median (IQR)	Number of studies (patients^b)	MCID pooled average (95% CI), I^{2 c}
Minimum clinically important difference for pain relief
Absolute change, mm
Mean change approach	8 to 40	29 (6517)	17 (14 to 23)	23 (6024)	17 (15 to 19), 93%
Threshold approach	10 to 35	6 (2331)	10 (10 to 10)	NA	NA
Relative change, %
Mean change approach	13 to 85	14 (1617)	23 (18 to 36)	11 (1397)	22 (19 to 26), 75%
Threshold approach	15 to 50	4 (534)	50 (33 to 50)	NA	NA
Substantial clinically important difference for pain relief
Absolute change, mm
Mean change approach	18 to 54	23 (6114)	32 (24 to 38)	21 (5891)	32 (27 to 38), 97%
Relative change, %
Mean change approach	36 to 78	11 (1397)	57 (45 to 65)	11 (1397)	57 (47 to 67), 94%
Minimum clinically important difference for pain worsening
Absolute change, mm
Mean change approach	−21 to –8	18 (3822)	−11 (–13 to –10)	16 (3644)	−12 (–14 to –11), 62%
Relative change, %
Mean change approach	−89 to –17	7 (918)	−44 (–90 to –16)	7 (918)	−35 (–47 to –23), 67%
Substantial clinically important difference for pain worsening
Absolute change, mm
Mean change approach	−66 to 0	16 (3663)	−21 (–28 to –16)	14 (3464)	−24 (–29 to –18), 71%
Relative change, %
Mean change approach	−292 to –18	7 (918)	−83 (–292 to –18)	7 (918)	−34 (–49 to –19), 20%

MCID minimum clinically important difference (mm or % reduction on a 100 mm scale), SCID substantial clinically important difference (mm or % reduction on a 100 mm scale), IQR inter-quartile range, NA not applicable
^aThe median is based on studies included in the pooled average as well as studies with unavailable standard errors
^bTotal number of patients in the included studies
^cI² is the percentage of the variability in results that is due to heterogeneity rather than sampling error (chance); I² of 0% to 40% might not be important, 30% to 60% may represent moderate heterogeneity, 50% to 90% may represent substantial heterogeneity, and 75% to 100% represents considerable heterogeneity

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