Potterat 1977.

Methods	Setting: El Paso, City‐county health department, Colorado, US Enrolment: participants were enrolled from February to September 1975 Follow up: index patient in patient referral group was re‐interviewed 7‐10 days after enrolment
Participants	187 index patients with gonorrhoea were randomised Inclusion criteria Heterosexual males with gonorrhoea Exclusion criteria Not specified
Interventions	Simple patient referral (n = 93) Study personnel had a short interview (3‐5 minutes) with index patient where the disease and importance of PN were discussed. Index patient received contact cards to be given to partners. Study personnel did not elicit any partner details Contract referral (n = 94) Study personnel had a longer interview (15‐20 minutes) with index patient and partner contact details were elicited. Index patient was informed that health services personnel would contact partners if they did not present at the health service within 7‐10 days
Outcomes	Partners testing positive for gonorrhoea (contact cards and self report by partner) Cost (clinic records)
Notes	Ethical approval details not given
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Alternately assigned "During the period February‐September 1975, we assigned all heterosexual male patients with gonorrhea diagnosed at the El Paso City‐County Health Department (Colorado) alternately to a Study or Control group"
Allocation concealment (selection bias)	Unclear risk	No information given
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome data for partners of all index patients available. In simple patient referral group, a second interview was performed to record contact details (91/93 index patients re‐interviewed). These details were used to contact partners to find out their subsequent clinical course and fate of contact slips
Selective reporting (reporting bias)	Low risk	Outcomes reported in methods section were reported in results section. Trial registries were not searched
Other bias	Unclear risk	Baseline comparability unclear
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding not possible
Blinding of outcome assessment (detection bias) All outcomes	High risk	The personnel knew to what group the participant belonged and, due to longer time spent with control group, this could have introduced detection bias. No specifics on test used. 9 contacts in the study group were also identified through field effort although field effort was not part of the original intervention in the study group ‐ detection bias