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Table 2 Newcastle–Ottawa scale (NOS) for assessing quality of observational studies

From: Clinical outcome comparison of percutaneous coronary intervention and bypass surgery in diabetic patients with coronary artery disease: a meta-analysis of randomized controlled trials and observational studies

Study

Selection

Comparability of the cohort

Outcome

Total score

Representativeness of the exposed cohort

Selection of the nonexposed cohort

Ascertainment of exposure

Outcome not present at baseline

Assessment of outcome

Enough follow-up duration

Adequate follow-up

Luo et al. [24]

*

*

*

*

**

*

*

*

9

Bangalore et al. [25, 34]

*

*

*

*

**

*

*

*

9

Marui et al. [26]

*

*

*

*

**

*

*

*

9

Naito et al. [27]

*

*

*

*

**

–

*

*

8

Yu et al. [28]

*

*

*

*

**

*

*

*

9

Zheng et al. [29]

*

*

*

*

**

*

*

*

9

Li et al. [30]

*

*

*

*

**

–

*

*

8

Ramanathan et al. [11]

*

*

*

*

**

*

*

*

9

Nagendran et al. [31]

*

*

*

*

**

*

*

*

9

  1. The scale assigns 4 points for selection, 2 points for comparability and 3 points for outcome (* 1 point; ** 2 points). Score of 5 to 6 considered as moderate quality and 7 to 9 as high quality