One study in which patients were given their first antiretroviral treatment demonstrated a slight decrease in bone density (a form of bone loss) in the first year of treatment with TDF and FTC (which closely resembles 3TC). This did however not cause any clinical problems. It was very reassuring to see that a complete recovery of the bone density was again seen after this first year. Nevertheless we want to collect more data about the possible effects on the bone metabolism and for this reason we will perform two bone density assessments during this study. Finally, there are indications that the renal function in patients who are treated with TDF may become slightly disturbed. It is as yet not clear which method can most accurately estimate and detect these slight changes in renal function. For this reason, we plan to compare a number of different methods to estimate renal function as part of this study. For this purpose a number of additional relevant measurements will be obtained using the blood samples which are already being collected as part of the study anyway.