Scientists have made a major advance in understanding the treatment of HIV which could see life-saving drugs extended to more than one million extra people at no additional cost. Researchers have discovered that routine laboratory testing of blood for signs of side-effects – long regarded as essential for HIV treatment – is unnecessary and a waste of time and money.

By abandoning routine laboratory testing, which is costly and requires sophisticated equipment only available in hospitals, the money saved could be used to buy and distribute extra anti-retroviral drugs.

In addition, removing the need for laboratory testing means treatment can be delivered in rural areas of Africa where two thirds of the continent's population live. At present one of the major bars to receiving treatment for many of those infected is that they live too far from the nearest hospital to be able to attend for testing.

Professor Diana Gibb, joint leader of the study, the largest ever conducted of anti-retroviral therapy in Africa, said: "At present there are 4 million people worldwide on treatment and 5 million who need treatment but aren't getting it. Our results show you could treat a third more than are currently being treated for the same cost. That is at least a million extra people."

Professor Gibb, of the UK Medical Research Council Clinical Trials Unit in London which funded the study, said: "These are very safe drugs. You don't need regular monitoring for side-effects. You don't need medically qualified people to deliver the pills. This is not just about money – it is about getting the treatment to where it is needed. Many people have to trek long distances to get their drugs instead of the drugs coming to them. But you can train healthcare workers to deliver the anti-retroviral pills to where people live."

The six-year trial involved 3,300 patients in Uganda and Zimbabwe given the standard HIV cocktail of three drugs contained in a single pill taken twice a day. One group had blood tests every three months and the results given to their doctor to check for drug side-effects and their CD4 cell count (to tell how well the drugs were working against the HIV). The other group had the same tests but the results were not given to their doctor unless they were seriously abnormal.

After five years 90 per cent were still alive in the first group compared to 87 per cent in the second group. The regular blood testing and medical checks made only 3 percentage points difference to the survival rate. The results are published today in The Lancet.

World Health Organisation guidelines say that treatment with anti-retroviral drugs should ideally be monitored with regular blood tests because that is what happens in the developed world. But they also say that where laboratory monitoring is not possible, giving treatment should be the priority.

In practice, countries have varied in their approach. In Malawi, treatment has been rolled out largely in the absence of laboratory testing while in South Africa leading scientists have refused to countenance it without testing.

Professor Gibb said, "In a time of economic crisis we need to get our priorities right. There are 5 million people who still need treatment."