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Table 1 Comparison of quality ratingsassigned to each paper using the Downs and Black (DB) scale and United States Preventative Services Task Force (USPSTF) system

From: Failure of a numerical quality assessment scale to identify potential risk of bias in a systematic review: a comparison study

References DB (internal validity score/13) USPSTF (internal validity rating) DB (external validity score/3) USPSTF (external validity rating) DB (total numerical scoreb/28 and rating) USPSTF (overall rating)
Bautch et al (1997 ) 8 Poor 1 Fair 18; fair Poor a
Bautch et al. (2000) 6 Fair 1 Fair 17; fair Fair
Bircan et al. (2008) 7 Fair 1 Fair 18; fair Fair
Dias et al. (2003) 8 Poor 1 Fair 18; fair Poor a
Ettinger et al. (1997) 11 Good 3 Fair 25; good Fair a
Evcik et al. (2002) 5 Fair 1 Good 15; fair Fair
Ferrell et al. (1997) 8 Fair 1 Fair 19; fair Fair
Holtgrefe et al. (2007) 7 Fair 3 Fair 18; fair Fair
Koldas Doğan et al. (2008) 7 Fair 0 Fair 17; fair Fair
Kovar et al. (1992) 9 Fair 3 Fair 21; good Fair a
Lemstra et al. (2005) 11 Good 3 Good 24; good Good
Martin et al. (1996) 7 Fair 1 Fair 16; fair Fair
Messier et al. (2004) 11 Fair 3 Fair 23; good Fair a
Meyer et al. (2000) 8 Poor 0 Poor 19; fair Poor a
Miller et al. (2006) 8 Fair 1 Fair 17; fair Fair
Nichols et al. (1994) 8 Fair 1 Fair 15; fair Fair
Rasmussen-Barr et al. (2009) 9 Good 2 Good 21; good Good
Rooks et al. (2007) 10 Good 3 Good 24; good Good
Talbot et al. (2003) 7 Fair 2 Good 18; fair Fair
Valim et al. (2003) 7 Fair 1 Poor 19; fair Fair
  1. Separate scores are given for each section (reporting, internal validity, external validity) and the overall total score. Papers were rated as “Excellent/good”, “fair” or “poor” depending on the numerical score assigned to the paper (Excellent/Good = 20–28; Fair = 15–19; Poor = <14).
  2. aItalicized studies indicate where the final grade assigned to the paper differed depending on the quality assessment tool used.
  3. bTotal possible score for the modified D&B scale = 28; reporting) = 11; internal validity = 13; external validity = 3; power = 1.
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