Estimates of life expectancy are of

Estimates of life expectancy are of obvious importance to people with HIV-1, and are essential to monitor and predict the progress of the HIV/AIDS epidemic and to plan health services. The Rwandan study reported by Sabin Nsanzimana and colleagues in is the first from sub-Saharan Africa to focus on the evolution of HIV-positive life expectancy during the scale-up of antiretroviral therapy, and is a welcome addition to a small body of data. The investigators show that the scale-up of antiretroviral therapy resulted in substantial gains in life expectancy, with near-normal life expectancy in individuals enrolled in care with little immunodeficiency. How reliable are estimates of life expectancy in people living with HIV? Life expectancy is the number of years that a person of a particular age would live, assuming that current age-specific mortality rates remain constant. Calculations might thus seem straightforward, but for people living with HIV in sub-Saharan Africa they are not. First, analyses rely on data for patients in treatment and care programmes, which might not be representative of all individuals living with HIV-1. Second, loss to follow-up of patients after the start of antiretroviral therapy is common. In the absence of functioning systems for vital statistics or outreach programmes to trace patients who were lost, mortality for these individuals remains unknown. To ignore the deaths in patients lost to follow-up substantially biases mortality downwards: death accounts for a substantial proportion of patients lost to follow-up. Last, the duration of follow-up needs to be standardised across calendar periods. The risk of death is not uniform after initiation of antiretroviral therapy, but falls with increasing duration of therapy. Nsanzimana and colleagues addressed all of these issues. The researchers limited the duration of follow-up to 3 years in all calendar periods, by myeloperoxidase with other studies (eg, an analysis from the UK and a collaborative study in high-income countries). The Rwandan study therefore controlled at least to some extent for survivor bias, although how similar lengths of follow-up were in the two calendar periods is unclear. Many patients from a nationally representative sample of clinics were included, which is an important strength of the study. Unfortunately, no information about mortality in patients lost to follow-up was obtained, but statistical adjustment was made assuming that about half of patients lost to follow-up had died. In Rwanda and many other countries in sub-Saharan Africa, vital statistics function poorly, with only a small number of deaths registered. The exception is South Africa, where coverage of vital registration is near universal and data from treatment and care programmes for HIV can be linked with mortality records to obtain accurate mortality estimates. The importance of the deaths among patients lost to follow-up in the Rwandan study is underlined by the much-higher estimates of life expectancy obtained when no adjustment was made, and uncertainty remains in this regard. How do the increases in life expectancy estimated for Rwanda compare with those of other studies, and how should exponential rate be interpreted? In Rwanda, the improvements were probably driven by changes over time in eligibility criteria for antiretroviral therapy and associated increases in CD4 counts at antiretroviral therapy initiation. Indeed, in a large-scale analysis of the International Epidemiologic Databases to Evaluate AIDS (IeDEA) that included patients starting antiretroviral therapy in 23 countries between 2002 and 2009, Rwanda had the highest annual increase in CD4 cell count at the start of therapy. However, whether any improvement in life expectancy would remain after controlling for these changes in baseline CD4 counts is unclear. Such an analysis addresses the question of whether or not the quality of HIV care has improved over time, which is important in view of the ever-increasing patient burden that treatment and care programmes for HIV face in sub-Saharan Africa.