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Table 4 Subgroup analyses of absolute minimum clinically important differences (MCIDs) for pain relief

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

Subgroup Analysis of medians Analysis of pooled average
Range, mm Number of studiesa (patientsb) MCID Median, mm (IQR) Number of studies (patientsb) MCID pooled average, mm (95% CI), I2 c
All studies 8–40 29 (6517) 17 (14–23) 23 (6024) 17 (15–19), 93%
Clinical conditions
 Post-operation paind 9–29 7 (731) 18 (10–25) 3 (361) 11 (8–14), 42%
 Trauma 16–20 2 (125) 18 (16–20) 2 (125) 18 (15–22), 11%
 Abdominal pain 18–25 2 (407) 21 (18–25) 2 (407) 21 (15–28), 91%
 Mixed patients at ED 8–24 7 (2418) 15 (11–21) 6 (2345) 16 (12–20), 90%
 Othere 10–40 5 (1980) 27 (23–34) 4 (1930) 22 (15–29), 92%
 Unspecified 13–21 6 (856) 16 (14–16) 6 (856) 16 (14–18), 72%
Definition of MCID
 One category improvement 8–34 24 (4504) 16 (13–21) 22 (4281) 16 (14–18), 91%
 Several categories improvement 23–29 3 (220) 25 (23–29) NA NA
 Meaningful change 27–40 2 (1793) 34 (27–40) 1 (1743) 27 (25–29), NA
Directionality of transition scale
 One-sided 9–40 5 (538) 18 (13–21) 3 (383) 15 (8–21), 93%
 Two-sided 8–25 19 (3962) 16 (13–20) 18 (3844) 16 (14–19), 91%
Pain scale
 Visual Analogue Scale 8–40 17 (3232) 17 (13–25) 15 (3109) 16 (13–19), 91%
 Numeric Rating Scale 10–23 7 (1268) 15 (14–21) 6 (1118) 16 (14–19), 91%
Measurements per patient
 Single 18–40 4 (461) 25 (23–29) 4 (2058) 22 (19–25), 0%
 Multiple
  With adjustment 10–18 9 (1104) 15 (13–16) 8 (1031) 15 (13–16), 34%
  Without Adjustment/unclear 8–25 11 (2935) 16 (10–21) 11 (2935) 16 (13–20), 95%
Risk of attrition bias
 Low 8–40 8 (1249) 19 (15–25) 8 (1249) 16 (14–18), 81%
 High or unclear 9–25 16 (3251) 16 (12–19) 13 (2978) 16 (13–19), 93%
Risk of non-representative sampling
 Low 8–25 6 (1187) 16 (10–21) 6 (1187) 16 (11–21), 96%
 High or unclear 9–40 18 (3313) 18 (14–24) 15 (3040) 16 (14–18), 87%
  1. IQR inter-quartile range, ED Emergency department, NA not applicable
  2. aThe median is based on studies included in the pooled average as well as studies with unavailable standard errors
  3. bTotal number of patients in studies
  4. 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
  5. dIncludes knee surgery, laparotomy, third molar extraction and mixed surgery (e.g. spinal fusion and splenectomy)
  6. eIncludes headache, low back pain, sickle cell crisis, rheumatic condition, and pain flare after external beam radiotherapy for bone metastases