TABLE 2.

Quality assessment of articles referenced

Author (reference), year	Study purpose	Literature	Design/bias	Sample	Outcome*	Exposure	Results	Conclusion/implication	Quality†
Douglas et al (52), 2008	PM	M	M	M	M	M	M	M	M
Ehde et al (36), 2003	M	M	PM	PM	M	M	M	M	M
Ehde et al (38), 2006	M	M	PM	PM	M	M	M	M	M
Forbes et al (59), 2006	PM	PM	PM	PM	M	M	M	M	PM
Glad et al (55), 2010	M	PM	PM	PM	M	PM	M	M	PM
Glad et al (54), 2011	M	PM	PM	PM	M	PM	M	M	PM
Julian et al (51), 2008	M	M	M	M	M	M	PM	M	M
Michalski et al (50), 2011	PM	PM	PM	PM	M	M	M	M	PM
Piwko et al (53), 2007	M	M	PM	M	M	M	M	M	M
Warnell (58), 1991	PM	PM	PM	PM	M	M	M	M	PM

Adapted from The Critical Review Form for Quantitative Studies developed by the McMaster University Occupational Therapy Evidence-Based Practice Research Group (39). Criteria for quality assessment included: purpose clearly stated; literature review was relevant; research design was appropriate to answer aims and no bias introduced into study; sample size justified, study sample described in detail, and informed consent gained; used reliable and validated outcome measures; exposure described in detail; results reported in terms of significance; analysis was appropriate, and clinical importance reported; conclusions and acknowledgement of limitations of the study were appropriate, and clinical implications reported.

^*Considering that employment status was the outcome of interest, and that in most studies employment was a sociodemographic variable which was gathered without a reliable and valid measurement tool, the criteria were modified for the quality assessment tool. Therefore, if the data on employment status in both pain and pain-free groups were provided, the reviewers considered it to be met (M);

^†Quality: <4 criteria met = not met (NM);4 or 5 criteria met = partially met (PM); >5 criteria met