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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.