START study

This page is part of Pocket ART, an easy guide to HIV treatment.


The START study showed that HIV treatment has important benefits for your health, even if your CD4 count is still high.

This international study was one of the most important HIV studies from the last ten years.

The study results quickly changed treatment guidelines. This included UK guidelines (BHIVA), international guidelines (WHO) and US guidelines. Previous guidelines said it was okay to wait until your CD4 counts dropped to a lower level.

START included more than 4600 HIV positive people from 35 countries. Everyone entered the study with a CD4 count above 500. Half of participants started ART straight away and half waited until their CD4 count reached 350.

Early ART more than halved the risk of a serious illness. Even though the actual risk was low – most people did well in both groups – the difference between the two groups was highly significant.

The benefit of treatment was seen for all important sub groups. For example in older and younger people (above/below 35), in men and women, in people living in both high- and low-income countries, and in people with and without risk for other important illnesses.

START showed that early ART was also safe and effective. About 98% of people who started treatment had an undetectable viral load at the end of their first year of treatment.

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