Absolute MCID was strongly associated with baseline pain , explaining approximately two-thirds of the variation , and to a lesser degree with the operational definition of minimum pain relief and clinical condition .
MCID  for chronic pain relief vary considerably .
Baseline pain is strongly associated with absolute , but not relative , measures .
To a much lesser degree , MCID is also influenced by the operational definition of relevant pain relief and possibly by clinical condition .
BACKGROUND The minimum clinical ly important difference ( MCID ) is used to interpret the relevance of treatment effects , e.g. , when developing clinical guidelines , evaluating trial results or planning sample sizes .
There is currently no agreement on an appropriate MCID in chronic pain and little is known about which context ual factors cause variation .
METHODS This is a systematic review .
Assessment of the minimum clinically important difference in pain, disability, and quality of life after anterior cervical discectomy and fusion: clinical article.
OBJECT Treatment effectiveness following spine surgery is usually gauged with the help of patient-reported outcome ( PRO ) question naires . Although these question naires assess pain , disability , and general health state , their numerical scores lack direct , clinical ly significant meaning . Thus , the concept of minimum clinical ly important difference ( MCID ) has been introduced , which indicates the smallest change in an outcome measure that reflects clinical ly meaningful improvement to patients . The authors set out to determine anterior cervical discectomy and fusion (ACDF)-specific MCID values for the visual analog scale ( VAS ) , Neck Disability Index ( NDI ) , 12-Item Short-Form Health Survey ( SF-12 ) , and EQ-5D ( the EuroQol health survey ) in patients undergoing ACDF for cervical radiculopathy . METHODS Data on 69 patients who underwent ACDF for cervical radiculopathy were collected in the authors ' web-based , prospect i ve registry during the study enrollment period . Patient-reported outcome question naires ( VAS-neck pain [ NP ] ) , VAS-arm pain [ AP ] , NDI , SF-12 , and EQ-5D ) were administered preoperatively and 3 months postoperatively , allowing 3-month change scores to be calculated . Four established calculation methods were used to calculate anchor-based MCID values using the North American Spine Society ( NASS ) patient satisfaction scale as the anchor : 1 ) average change , 2 ) minimum detectable change ( MDC ) , 3 ) change difference , and 4 ) receiver operating characteristic ( ROC ) curve analysis . RESULTS Sixty-one patients ( 88 % ) were available at follow-up . At 3 months postoperatively , statistically significant improvement ( p < 0.001 ) was observed for the following PROs assessed : VAS-NP ( 2.7 ± 3.3 ) , VAS-AP ( 3.7 ± 3.6 ) , NDI ( 23.2 % ± 19.7 % ) , SF-12 physical component score ( PCS ; 10.7 ± 9.7 ) , and EQ-5D ( 0.20 ± 0.23 QALY ) . Improvement on the SF-12 mental component score ( MCS ) trended toward significance ( 3.4 ± 11.4 , p = 0.07 ) . The 4 MCID calculation methods generated a range of MCID values for each of the PROs : VAS-NP 2.6 - 4.0 , VAS-AP 2.4 - 4.2 , NDI 16.0%-27.6 % , SF-12 PCS 7.0 - 12.2 , SF-12 MCS 0.0 - 7.2 , and EQ-5D 0.05 - 0.24 QALY . The maximum area under the curve ( AUC ) was observed for NDI ( 0.80 ) , and the minimum AUC was observed for SF-12 MCS ( 0.66 ) and EQ-5D ( 0.67 ) . Based on the MDC approach , the MCID threshold was 2.6 points for VAS-NP , 4.1 points for VAS-AP , 17.3 % for NDI , 8.1 points for SF-12 PCS , 4.7 points for SF-12 MCS , and 0.24 QALY for EQ-5D . The mean improvement in patient scores at 3 months surpassed the MCID threshold for VAS-NP , NDI , and SF-12 PCS but not for VAS-AP , SF-12 MCS , and EQ-5D . CONCLUSIONS The ACDF-specific MCID is highly variable depending on the calculation technique used . The MDC approach seems to be most appropriate for MCID calculations in the ACDF population , as it provided a threshold value above the 95 % confidence interval of nonresponders ( greater than the measurement error ) and was closest to the average change of most PROs reported by responders . When the MDC method was applied with the NASS patient satisfaction scale as the anchor , the MCID thresholds were 2.6 points for VAS-NP , 4.1 points for VAS-AP , 17.3 % for NDI , 8.1 points for SF-12 PCS , 4.7 points for SF-12 MCS , and 0.24 QALY for EQ-5D
Absolute MCID was strongly associated with baseline pain , explaining approximately two-thirds of the variation , and to a lesser degree with the operational definition of minimum pain relief and clinical condition .
MCID  for chronic pain relief vary considerably .
Baseline pain is strongly associated with absolute , but not relative , measures .
To a much lesser degree , MCID is also influenced by the operational definition of relevant pain relief and possibly by clinical condition .
BACKGROUND The minimum clinical ly important difference ( MCID ) is used to interpret the relevance of treatment effects , e.g. , when developing clinical guidelines , evaluating trial results or planning sample sizes .
There is currently no agreement on an appropriate MCID in chronic pain and little is known about which context ual factors cause variation .
METHODS This is a systematic review .