What works best? Getting the evidence right

The health advice we get in the popular media can be downright confusing. But help is at hand in the form of the dedicated group of scientists who comprise the Cochrane Collaboration. ELMIEN WOLVAARDT investigates.

Have you ever been confused by conflicting research reports? Just when you think chocolate is safe to eat again, a new research study shows that it is bad for your health!

What should we believe? And who should we believe?

Although the chocolate example might be trivial, consider what people with HIV/ AIDS must go through when they read conflicting reports about the effectiveness of anti-retroviral drugs - especially when the resulting confusion can lead to delays in the provision of these life-saving medicines.

In fact, both examples point to the problematic nature of scientific research.

Let's assume two research groups are investigating the effectiveness of a new migraine drug. While one group might test the drug on thousands of different people, another group might do a more in-depth study, but on only a very small number of people.

In addition, the methods used by each group, and the way the results are collected and analysed, can affect their conclusions.

The upshot is that not all studies are born equal. Unfortunately, people in need of health care - as well as those who give it - aren't necessarily equipped ( nor have the time) to evaluate all the different studies about a specific drug or health intervention. This can lead to much confusion, especially when two or more studies have conflicting results.

It is precisely for this reason that the Cochrane Collaboration was established in 1993: to help people make informed decisions about health care, based on the best available evidence.

'It is important to know that the health care one receives or offers actually works,' says Dr Taryn Young, specialist scientist at the South African Cochrane Centre based at the Medical Research Council. It is one of 13 Cochrane Centres in the world.

The members of the Cochrane Collaboration carefully identify and evaluate all the available evidence about a particular health intervention, and make recommendations about the benefits and safety of such interventions. This process is known as a systematic review.

'A systematic review tries to answer a specific question about a health intervention or treatment,' says Dr Young. 'The group conducting this review then evaluates all the available studies - regardless of language, country, or publication status - and synthesizes the results.

'This gives us our answer: whether the treatment works or not, how well it works and what the side effects are.'

However, a simple 'yes' or 'no' answer isn't always possible. Says Dr Young: 'In some cases, we discover that too little evidence exists for us to draw any conclusions either way.'

A recent example of this is the question of HIV/ AIDS and male circumcision. Although several observational studies have suggested that circumcised males are to some extent protected against HIV infection, a Cochrane review has shown that too little evidence exists to prove - or disprove - this assertion. Based on this review, the South African Cochrane Centre advised that the results from three trials currently underway in Kenya, Uganda and South Africa should be awaited before any further recommendations about circumcision can be made.

Although researchers might be under pressure to provide 'yes' or 'no' answers to health questions, it is always much safer to be alert to the times when we don't yet know enough. This is in line with what Hippocrates, the celebrated Greek physician, wrote: 'As to diseases, make a habit of two things: to help; or at least to do no harm.'