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 .
Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid?
OBJECTIVE To examine the test-retest reliability , validity , and responsiveness of several outcome measures in the treatment of patellofemoral pain . DESIGN Evaluation of the clinimetric properties of individual outcome measures for patellofemoral pain treatment , using data collected from a previously published r and omized controlled trial ( RCT ) . SETTING General community and private practice . PARTICIPANTS The data from 71 persons enrolled in an RCT of a conservative intervention for patellofemoral pain were used to evaluate the measures ' validity and responsiveness . A subset of this cohort ( n=20 ) was used to assess reliability . INTERVENTIONS Not applicable . MAIN OUTCOME MEASURES Three  10-cm visual analog scales ( VASs ) for usual pain ( VAS-U ) , worst pain ( VAS-W ) , and pain on 6 aggravating activities ( walking , running , squatting , sitting , ascending and descending stairs ) ( VAS-activity ) ; the Functional Index Question naire ( FIQ ) ; the Anterior Knee Pain Scale ( AKPS ) ; and the global rating of change . RESULTS The test-retest reliability ranged from poor ( intraclass correlation coefficient [ICC]=.49 ) to good ( ICC=.83 ) , and the measures correlated moderately with each other ( r range,.56-.72 ) . Median change scores differed significantly between improved and unimproved persons for all measures . The effect sizes for VAS-U ( .79 ) , VAS-W ( .88 ) , and the AKPS ( .98 ) were large , indicating greater responsiveness than the FIQ ( .37 ) and VAS-activity ( .66 ) . Similarly , the AKPS and VAS-W were the most efficient measures for detecting a treatment effect when compared with a reference measure ( VAS-U , which was assigned a value of 1 ) . The minimal difference that patients or clinicians consider clinical ly important for the AKPS is 10 ( out of 100 ) points and for the VAS it is 2 cm ( out of 10 cm ) . CONCLUSIONS The AKPS and VAS for usual or worst pain are reliable , valid , and responsive and are therefore recommended for future clinical trials or clinical practice in assessing treatment outcome in persons with patellofemoral pain
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 .