# Table 1

Results of the quality assessment of the 22 included articles

Author and year of publicationStudy ParticipationStudy AttritionOutcome MeasurementStatistical Analysis and ReportingRisk of bias assessment
General population studies
Abujam et al. 2014 [49]NoN/AYesYesHigh
Auvinen et al. 2009 [50]NoN/APartlyYesHigh
Bishop et al. 2012 [51]NoN/AYesYesHigh
Diepenmaat et al. 2006 [36]YesN/AYesYesLow
Ehrmann Feldman et al. 2002 [37]YesYesPartlyYesLow
El-Metwally et al. 2006 [15]YesN/AYesYesLow
Hoftun et al. 2011 [38]YesN/AYesYesLow
Hulsegge et al. 2011 [47]PartlyYesPartlyYesMedium
Jespersen et al. 2014 [14]YesYesYesYesLow
Jespersen et al. 2015 [39]YesN/AYesYesLow
Krul et al. 2009 [40]YesN/AYesYesLow
Mikkelsson et al. 1997 [41]YesN/AYesYesLow
Molgaard et al. 2011 [48]PartlyN/AYesYesMedium
Rathleff et al. 2013 [42]YesN/AYesYesLow
Shrier et al. 2001 [43]YesYesPartlyYesLow
Slowinska et al. 2015 [68]NoN/AYesPartlyHigh
Smedbraten et al. 1998 [52]NoN/AYesYesHigh
Verhagen et al. 2009 [54]YesNoYesYesHigh
Clinical studies
Bot et al. 2005 [44]YesN/Aa YesPartlyLow
Henschke et al. 2014 [45]YesN/Aa YesYesLow
Van der Waal et al. 2006 [46]YesN/Aa YesYesLow
aAttrition bias may be present, but very small.
If present, it will be on general practitioners level, and not on patient level