1/1996-12/2008

Switzerland

Background: Immigrants from low-income regions form a large and increasing proportion of patients in the Swiss HIV cohort and in other European and North-American HIV cohorts. Previous research on immigration in the Swiss HIV Cohort Study (SHCS) has focussed mainly on immigrants from Sub-Sahara-Africa. Factors other than therapy-outcome such as demographic patterns, adherence to cohort-visits and retention into the cohort have not been investigated in detail and are of particular interest when comparing patients of different regional and cultural background. Experience during clinical consultations suggests that immigrants are less willing to participate in the SHCS. Yet, it has been investigated to date only at one single SHCS centre how representative the SHCS is for immigrant patients. Furthermore, there is a general demand to know how many patients not participating in the SHCS are cared for by cohort clinics-and practices. Study Aims: This study will consist of three sections: 1. Immigration-and gender trends will be assessed. Demographic and clinical factors by immigrant group in relation to HIV-stage at enrolment into the SHCS will be investigated. The first section is mainly descriptive. 2. Treatment outcome to combined antiretroviral therapy (c-ART) according to region of origin will be assessed. Adherence to cART and retention into the cohort will be studied and compared between immigrant groups of different regional origin taking into account co- morbidities, Combination Antiretroviral Therapy (cART), time spent in the HIV-cohort. The second section is mainly analytical. 3. A survey will be carried out among HIV patients not participating in the SHCS to quantify potential participation bias with respect to treatment status, origin, transmission category and gender. Study Design: Aims 1-2: Analysis of available cohort data from all patients with a regular follow-up visit between 01/01/1996 and 31/12/2008. Aim 3: Survey among SHCS centres, affiliated hospitals and private practices.

Objective Data from observational cohorts may be influenced by population structure and loss to follow-up (LTFU). Quality of care may be associated with participation in cohort networks. We aimed to study the participation, characteristics and retention rates of immigrants in the Swiss HIV Cohort Study (SHCS). Methods: We compared enrolment over time (1996-1999, 2000-2003 and 2004-2008) and LTFU between individuals from different geographical regions. In 2008, we performed a cross-sectional survey to investigate the proportion of individuals not participating in the SHCS but who were in care at SHCS institutions. Predictors for LTFU were analysed using Cox proportional hazard models, and those for nonparticipation using logistic regression. Results: A total of 7840 individuals entered the SHCS during the observation period. The proportion of immigrants increased over time, especially the proportion of women from sub-Saharan Africa, which increased from 21 to 48% during the observation period. Overall LTFU was 3.76 (95% confidence interval (CI) 3.58-3.95)/100, with the highest hazard ratio in men from sub-Saharan Africa (2.82/100 patient-years; 95% CI 2.30-3.46/100), compared with men from northwestern countries. Other predictors for LTFU were age o30 years, lower education, injecting drug use, and higher baseline CD4 cell counts. Participants taking antiretroviral therapy had reduced LTFU. The survey showed that 84% of HIV-infected patients in care at SHCS institutions were enrolled in the cohort. Nonparticipation was more likely among men from non-European regions (odds ratio 2.73; 95% CI 2.29-3.24), women from sub-Saharan Africa (odds ratio 3.01; 95% CI 2.40-3.77) and women from Latin America/Caribbean (odds ratio 2.10; 95% CI 1.30-3.39). Conclusions: Numbers of HIV-infected immigrants are increasing but they are underrepresented in the SHCS, and immigrants are more likely to be lost to follow-up.