1. Royal Free & University College London Medical School, Royal Free Center for HIV Medicine & Department of Primary Care & Population Sciences, Royal Free Campus, Rowland Hill St., London, NW3 2PF, UK.
2. Royal Free and University College Medical School, Royal Free Center for HIV Medicine & Department of Primary Care and Population Sciences, Royal Free Campus, Rowland Hill St, London NW3 2PF, UK.
3. School of Public Health, University of Minnesota, Minneapolis, MN 55414 USA.
4. Copenhagen HIV Program, Hvidovre University Hospital, Hvidovre, Denmark.