Table 2
Characteristics of case–control studies for ulcerative colitis and Crohn’s disease studies
Study characteristics and demographics Study quality characteristics
Author (year) Country No. of cases No. of controls Source of controls Controls matched for: Methods of diagnosis defined Diagnosis based on recognized criteria Urban/rural defined Urban population >10,000 Time of exposure Multiple levels of exposure
Ulcerative Colitis
Parrello 1997 [26] Italy 509 657 Attending orthopedic and surgical clinics Sex, age, year of diagnosis Yes Yes No No Time of data collection No
Feeney 2002 [17] UK 137 137 Functional GI Disorders Sex, age Yes Yes No No Childhood (age 0–5) No
Bernstein 2007 [27] Canada 137 310 Manitoba Health Population Registry Sex, age No N/A No No N/A No
Jiang 2007 [28] China 177 177 Neighbours or colleagues Sex, age Yes Yes No No Childhood No
Radon 2007 [54] Germany 304 1481 Strabismus surgery Age No N/A No No Time of data collection No
Martinez Salmeron 1994 [46] Spain 63 63 Hospital Sex, age Yes Yes Yes No Time of data collection No
Ekbom 1990 [8] Sweden 164 328 Live births between 1924–1957 in Uppsala County Date of birth, sex, and maternal age or parity Yes Yes Yes No Time of birth No
Crohn’s Disease
Feeney 2002 [17] UK 139 139 Functional GI disorders Sex, age Yes Yes No No Childhood (age 0–5) No
Bernstein 2007 [27] Canada 235 310 Manitoba Health Population Registry Sex, age No N/A No No N/A No
Ponsonby 2009 [53] Australia 278 998321 Live births from 1983–1998 in Victoria Age Yes No Yes No Childhood (age 0–6) No
Malekzadeh 2009 [16] Iran 196 207 IBS treated by an expert gastroenterologist Age Yes Yes No No Childhood (before 16th birthday) No
Radon 2007 [54] Germany 444 1481 Strabismus surgery Age No N/A No No Time of data collection No
Thompson 1998 [29] England, Wales 291 1682 Same GP Sex, age No N/A No No N/A No
Wurzelmann 1994 [13] United States 322 262 Closest neighbour Sex, age, race No N/A No No Childhood (age 0–5) Yes
Martinez Salmeron 1994 [46] Spain 30 30 Hospital Sex, age Yes Yes Yes No Time of data collection No
Ekbom 1990 [8] Sweden 93 186 Live births between 1924–1957 in Uppsala County Date of birth, sex, and maternal age or parity Yes Yes Yes No Time of birth No

Soon et al. BMC Gastroenterology 2012 12:51   doi:10.1186/1471-230X-12-51

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