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Table 3 Risk of bias using the Downs and Black toola for retrospective cohort studies (n = 12 studies)

From: The effect of surgery on the outcome of treatment for multidrug-resistant tuberculosis: a systematic review and meta-analysis

First author, year of publication

Reporting (maximum of 11)

External validity (maximum of 3)

Internal validity, bias (maximum of 7)

Internal validity, confounding (maximum of 6)

Total (maximum of 27)

Dravniece 2009 [26]

3

0

2

2

7

Karagoz 2009 [34]

6

2

4

3

15

Keshavjee 2008 [33]

7

1

4

2

14

Kim 2007 [31]

7

0

2

1

10

Kim 2008 [32]

6

1

4

3

14

Kwak 2015 [30]

7

0

4

2

13

Leimane 2005 [23]

10

2

3

4

19

Mitnick 2008 [24]

5

2

4

2

13

Tahaoglu 2001 [28]

4

1

1

2

8

Torun 2007 [25]

8

1

3

2

14

Kwon 2008 [22]

9

2

3

4

18

Shean 2008 [29]

6

2

4

2

14

  1. aTwenty-seven criteria are used to assess risk of bias. Each criterion is scored as Yes (1), No (0) or unable to determine (0). An overall score is calculated by summation, as well as four sub-scales representing “reporting” (total of 11; includes power criterion), “external validity” (total of 3), “internal validity, bias” (total of 7) and “Internal validity, confounding” (total of 6). Higher scores represent lower risk of bias
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BMC Infectious Diseases

ISSN: 1471-2334

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