Table 2

Quality of cohort studies examining the effect of circumcision on urinary tract infection in male subjects

Reference	Definition of UTI	Determination of circumcision status	Exclusion criteria	Follow up	Adjustment for confounding variables
Reference	Definition of UTI	Determination of circumcision status	Exclusion criteria	Follow up	Age	SES	Ethnicity
ICD-9,International Classification of Diseases, 9th revision; KPNC, Kaiser Permanente Medical Care Program, Northern California, USA; OHIP, Ontario Health Insurance Plan; SES, socioeconomic status.
Schoen et al²²	>10⁸/l pure growth in 90% from any means of collection	Inpatients: ICD-9 coding for circumcision in neonatal hospital stay	Patient not within health plan for full duration of study	<1 year	No	No	No
	Source unknown in 4%	Outpatients: ICD-9 from KPNC database for outpatient circumcision
	Determined by retrospective database search and confirmed by review of case records of random selection of 52 cases

To et al¹	Inpatients: ICD-9 coding (kidney infection, cystitis, urethritis or urinary tract infection)	The Canadian classification procedure code during the first month of life	Older than 1 month of age at time of circumcision, multiple birth, stillbirth, birth complications and lack of health care number	2–3 years for inpatient cases	No	Yes	No
	Outpatients: OHIP data			<1 year for outpatient cases
	Determined by retrospective database search			<1 year for outpatient cases

Wiswell and Hachey⁶	Not specified	US Army patient administration systems and biostatistics activity database	Bag urine specimen, congenital abnormality, or predisposition to UTI (not specified)	<1 year	No	No	No
Wiswell and Hachey⁶	Determined by retrospective database search

Wiswell et al⁵	Not specified	US Army patient administration systems and biostatistics activity database	Congenital abnormality or predisposition to UTI (not specified)	<1 year	No	No	No
Wiswell et al⁵	Determined by retrospective database search