Table 2.

The Newcastle-Ottawa Scale

Study	Selectiona				Comparabilityb		Outcomec			Quality score
	Representative of treat group	Representative of refer group	Assignment for treatment	Outcome in baseline	For normal baseline	For special baseline	Assessment of outcome	Adequate follow-time	Adequate follow-up
Cheung [19]	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	9
Hitman [20]	No	No	Yes	No	No	Yes	Yes	Yes	No	5
Bello [26]	Yes	Yes	Yes	No	No	No	Yes	Yes	No	6
Fuller [17]	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	7
Hankey [24]	Yes	Yes	Yes	No	No	No	Yes	Yes	No	6
Cohen [13]	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	7
Hjelmgren [29]	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	7
Ono [18]	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	9
Drinkwater [15]	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	7
Hägg [23]	No	No	Yes	No	Yes	No	Yes	Yes	No	5
Kawasaki [25]	Yes	Yes	Yes	No	Yes	No	Yes	Yes	No	7
Gerstein [22]	Yes	Yes	Yes	No	No	No	Yes	Yes	No	6
Barlovic [28]	Yes	Yes	Yes	No	No	No	Yes	Yes	No	6
Wong [14]	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	9
Lip [27]	No	No	Yes	No	No	No	Yes	Yes	Yes	5
Landers [30]	Yes	Yes	Yes	No	NA	NA	Yes	Yes	Yes	7
Chou [10]	No	No	Yes	No	No	No	Yes	Yes	Yes	5
Protopsaltis [21]	Yes	Yes	Yes	No	No	No	No	Yes	Yes	6
Klein [16]	Yes	Yes	Yes	No	Yes	Yes	Yes	No	Yes	7

^a Representative if the study is countrywide, not if it is a province/city/continent.

^b General baseline: sex/body mass index/vital signs, etc; special baseline: high-density lipoprotein/glycated hemoglobin A_1c, etc; comparable if 1 item or less is significant, not if 2 items or more are significant.

^c Score if follow-up time has been 5 years or more, and score for missed follow-up rate is less than or equal to 5%.

^d If the relevant scoring item is not mentioned, this item will be treated as 0.5 points; and all decimal places will be discarded when the score is counted.