Tracing patients lost to follow up in an urban slum: cooperation between a clinic and an NGO network in Mumbai, India

•Overall 38 out of 819 (4.6%) patients registered in the clinic were LTFU •Most patients were lost during the first year of the project while the rates were <2% during the last 2 years. •Few respondents reported experience of NGO tracing. •Phoning the day before an appointment was perceived the most useful intervention to avoid missed appointments. •Fear of forced disclosure of HIV arising from home visits was revealed.