South Africans show impact of HIV on rural mums and babies

Julian Meldrum
Estimated reading time 2 minutes
This article is more than 22 years old.

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.

Glossary

ribonucleic acid (RNA)

The chemical structure that carries genetic instructions for protein synthesis. Although DNA is the primary genetic material of cells, RNA is the genetic material for some viruses like HIV.

 

p24

An HIV antigen that makes up most of the HIV viral core. High levels of p24 are present in the blood during the short period between HIV infection and seroconversion, before fading away. Since p24 antigen is usually detectable a few days before HIV antibodies, a diagnostic test that can detect p24 has a slightly shorter window period than a test that only detects antibodies.

capacity

In discussions of consent for medical treatment, the ability of a person to make a decision for themselves and understand its implications. Young children, people who are unconscious and some people with mental health problems may lack capacity. In the context of health services, the staff and resources that are available for patient care.

subtype

In HIV, different strains which can be grouped according to their genes. HIV-1 is classified into three ‘groups,’ M, N, and O. Most HIV-1 is in group M which is further divided into subtypes, A, B, C and D etc. Subtype B is most common in Europe and North America, whilst A, C and D are most important worldwide.

protein

A substance which forms the structure of most cells and enzymes.

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.

References

Rollins NC et al. Prevalence, incidence and mother-to-child transmission of HIV-1 in rural South Africa. Lancet, 360: 389-390, 3 August 2002.

Withum DG et al. Evaluation of an ultrasensitive p24 antigen assay (UPTA) for use in the diagnosis of pediatric HIV-1 infection XIV International Conference on AIDS, Barcelona, abstract ThPeB7227, 2002.

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