Table 2 The six studies meeting the quality criteria according to Straus et al9
StudyParticipants employees at start of study?Participants work disabled because of MI or cLBP at start of study?Follow-up ⩾1 year?Loss to follow-up ⩽20%Adjustment for other prognostic factors?Justification for used set of prognostic factors?Total
Froom et al 199910YesYesYesYesYesYes6
Boudrez and de Backer 200011YesYesYesYesYesYes6
Hansson and Hannsson 200012YesYesYesYesYesYes6
Van der Giezen et al 200013YesYesYesYesYesYes6
Nielsen et al 200414YesYesYesYesYesNot mentioned5
Hamalainen et al 200415YesYesYesNot mentionedYesYes5