Katz 1988.

Methods	Setting: public STI clinic, Indianapolis, Indiana, US Enrolment: male participants with NGU enrolled between July and December 1985 Follow‐up: no follow‐up stated for index patients
Participants	678 index patients with NGU were randomised to 1 of 3 interventions Inclusion criteria Heterosexual male Microscopically confirmed NGU Exclusion criteria No exclusion criteria specified
Interventions	Simple patient referral with nurse (n = 217) Nurse providing health education and referral letters. No contact details of partners were requested Patient referral with contact tracer (DIS) (n = 240) Counselling with contact tracer, partners names recorded but no referral letters given and no partner contact details elicited Provider referral by contact tracer (n = 221) Interview with contact tracer, contact details of partners taken, attempt to contact by phone calls, letters or visits
Outcomes	Cost‐effectiveness (clinic records) Partners located (contact tracer telephoned partner, send letter via post or field visit) Partners treated (partners were matched to index patient by referral letter or by computerised database)
Notes	Ethical approval details not mentioned The effectiveness of interventions 1 and 2 underestimated due to bias in outcome assessment: partners choosing to be treated at other health services were not counted for these groups
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Patients were randomised ‐ no details given
Allocation concealment (selection bias)	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome data for all partners of index patients randomised available
Selective reporting (reporting bias)	Low risk	Outcomes reported in methods section were reported in results section. Trial registries not searched
Other bias	Low risk	No other bias identified
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participant and personnel not blinded
Blinding of outcome assessment (detection bias) All outcomes	High risk	No blinding. Partners were matched to the index patient by the referral letter or the clinic's computerised database in group 1 and 2. In group 3, the contact details were taken and partners were contacted by the provider