Table 2.

Assessment of study quality.

Quality indicators from Newcastle-Ottawa Scale	Kumor et al. [24]	Gonullu et al. [26]	Nakajima et al. [23]	Danese et al. [27]	Joshi et al. [18]	Lu et al. [28]	Tulubas et al. [21]	Wägsäter et al. [29]	Kosova et al. [25]	Hillenbrand et al. [32]
Independent validation of case definition	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	No	No
Consecutive or obviously representative series of cases	No	No	Yes	No	No	No	Yes	Yes	Yes	No
Community controls	No	No	No	No	No	No	No	Yes	No	No
Controls have negative colonoscopy	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No
Study controls for age/gender	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes
Study controls for BMI	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No
Secure record of resistin levels with blinded interview	No	No	No	No	No	No	No	No	No	No
The same method of resistin measurement for cases and controls	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
The same nonresponse rate for cases and controls	No	No	No	No	No	No	No	No	No	No
Score	5	5	6	5	3	2	6	6	2	2