Research methods determine results
Jan 27, 2009
EDITOR—The World Health Organisation (WHO) reports that “circumcision reduces the risk of HIV infection by up to 60%â€. There are issues with this number. In Uganda the male Bagisu, and Muslims circumcise.
EDITOR—The World Health Organisation (WHO) reports that “circumcision reduces the risk of HIV infection by up to 60%â€. There are issues with this number. In Uganda the male Bagisu, and Muslims circumcise.
But they are also dying of AIDS. One day, a professor of critical thinking once said that university lecturers wrote a proposal and they reported their support for it with a number. It was absolute risk.
The funders of their ministry of health rejected the proposal. They again supported the need for the same programme with another number.
They calculated relative risk. With relative risk—a statistic—the same officials of their ministry of health accepted to fund the project. From this observation, it is clear that not only professionals but also the public may fail to notice the difference between absolute and relative risk. let us look at the example of the Rakai study, done in Uganda, which reported the benefit of male circumcision in the control of the spread of HIV infection.
The report of this study was published in The Lancet in 2007. We critically examined that report. The reduction in risk in the report is about 50% among males aged 15-49 years.
We observed that the researchers trumpeted the relative risk. Relative risk can make things appear bigger than they really are! So, for one to make a quality decision, we must always ask for the absolute risk. In that study, the absolute risk is nine people in 1,000.
This means when you spend on circumcising 1,000 people, nine people will get infected. And when you don’t circumcise 1,000 Ugandan males in Rakai aged 15-49 years people, 18 will get infected.
That is, by spending on circumcising 1,000 males you will save 18-9 = 9 people against HIV infection. This really isn’t a big number especially when you have to manage malaria, tuberculosis, meningitis, typhoid , etc. Now, we are about 30 million Ugandans.
If we factor in the age bracket 15-49 years, and gender, 135,000 Ugandan males will be protected against HIV infection by circumcision according to that study. But we can only come to this apparently big number if we spent money on accessing all the 30 million people.
And note that we computed this figure based only on the statistic the researchers used: Relative risk. Issues like the time the penis takes to heal (about a month) were not considered. But during the study, the uncircumcised group must have had sexual intercourse.
This means for a whole month, while the circumcised were not exposed to risk, the uncircumcised were. And this was a serious flaw in the study design. Unfortunately, when the WHO report relative risk of up to 60%, people think it is really big, and this may therefore generate false hope among the circumcised.
To know whether circumcision protects against HIV infection or not, it is wise to study HIV status of males who are already circumcised and those who are not. Even then, a number of factors, beyond the scope of the purpose here have to be considered as well.
Science is proving things; therefore there is science in all disciplines. But we should learn not only to scrutinise the method used by the researchers, but also to understand the statistic used to come to the conclusions as well as the associated assumptions. This will save resources for priority methods of taming the disease. These include behavioural change plays, songs, being faithful, or abstaining until marriage.
George Kibumba
Makerere University
But they are also dying of AIDS. One day, a professor of critical thinking once said that university lecturers wrote a proposal and they reported their support for it with a number. It was absolute risk.
The funders of their ministry of health rejected the proposal. They again supported the need for the same programme with another number.
They calculated relative risk. With relative risk—a statistic—the same officials of their ministry of health accepted to fund the project. From this observation, it is clear that not only professionals but also the public may fail to notice the difference between absolute and relative risk. let us look at the example of the Rakai study, done in Uganda, which reported the benefit of male circumcision in the control of the spread of HIV infection.
The report of this study was published in The Lancet in 2007. We critically examined that report. The reduction in risk in the report is about 50% among males aged 15-49 years.
We observed that the researchers trumpeted the relative risk. Relative risk can make things appear bigger than they really are! So, for one to make a quality decision, we must always ask for the absolute risk. In that study, the absolute risk is nine people in 1,000.
This means when you spend on circumcising 1,000 people, nine people will get infected. And when you don’t circumcise 1,000 Ugandan males in Rakai aged 15-49 years people, 18 will get infected.
That is, by spending on circumcising 1,000 males you will save 18-9 = 9 people against HIV infection. This really isn’t a big number especially when you have to manage malaria, tuberculosis, meningitis, typhoid , etc. Now, we are about 30 million Ugandans.
If we factor in the age bracket 15-49 years, and gender, 135,000 Ugandan males will be protected against HIV infection by circumcision according to that study. But we can only come to this apparently big number if we spent money on accessing all the 30 million people.
And note that we computed this figure based only on the statistic the researchers used: Relative risk. Issues like the time the penis takes to heal (about a month) were not considered. But during the study, the uncircumcised group must have had sexual intercourse.
This means for a whole month, while the circumcised were not exposed to risk, the uncircumcised were. And this was a serious flaw in the study design. Unfortunately, when the WHO report relative risk of up to 60%, people think it is really big, and this may therefore generate false hope among the circumcised.
To know whether circumcision protects against HIV infection or not, it is wise to study HIV status of males who are already circumcised and those who are not. Even then, a number of factors, beyond the scope of the purpose here have to be considered as well.
Science is proving things; therefore there is science in all disciplines. But we should learn not only to scrutinise the method used by the researchers, but also to understand the statistic used to come to the conclusions as well as the associated assumptions. This will save resources for priority methods of taming the disease. These include behavioural change plays, songs, being faithful, or abstaining until marriage.
George Kibumba
Makerere University