South Africans show impact of HIV on rural mums and babies

The use of RNA tests (NucliSens QL, Organon Teknika) as well as dual ELISA antibody tests on dried blood spot samples is described by a South African research team in The Lancet this week, as a practical way to extend population surveys of HIV transmission from selected urban clinics to rural areas (Rollins).

Working with a number of clinics in rural KwaZulu Natal, South Africa’s worst-affected province, the researchers have shown that it is possible to use dried blood spots to transport samples safely for testing at a central laboratory, to get an accurate picture of rates of HIV infection among mothers and their babies.

1,303 mothers attending immunization clinics with their babies were asked for permission to take pin-prick blood samples from a finger (mothers) and a heel (babies). These were then sent to a central laboratory for testing. It is not clear from the published report whether all testing was anonymous, or whether mothers had the option to access test results if they wanted to.

With this study, the researchers have shown that HIV rates among young mothers in parts of rural KwaZulu Natal are up to 40% among mothers aged 21-30 in communities close to a major highway, and only slightly lower – at 29 to 34% - in communities more than 50km away from main transport routes. Women under 25 continue to be at high risk of HIV infection, and rates of transmission to babies born to HIV positive mothers, where 95% of babies are breast-fed, are around 24% by six months of age. No babies tested positive who had been born to HIV negative mothers. Babies that were positive for antibodies but negative on RNA tests were classified as uninfected; mothers who tested negative for antibodies were tested using RNA tests to identify recent infections.

Testing programmes of this kind will need to be developed, along with lower-cost testing systems, to monitor the success of programmes to prevent transmission and to judge the need for treatment. In some parts of the world, such as the Caribbean, the provision of drugs to prevent mother-to-child transmission is running ahead of laboratory capacity to test mothers and babies.

Lower-cost and more simply operated testing systems that are being developed include blood tests for the HIV core protein p24, including a heating stage to remove the 'masking' effect of antibodies against p24. This gets round the problem, that babies have their mother's antibodies for the first few months of their lives, so antibody tests do not indicate whether a baby is living with HIV. A commercial test from the US company PerkinElmer Life Sciences is now being studied as an alternative to RNA tests for this purpose (Withum), although there is still some doubt as to whether it works equally well for all HIV subtypes.