Ideally programmes should carry out sequential prevalence studies or cohort studies in infants. These studies would reliably estimate infant HIV infections under operational conditions rather than extrapolate figures from clinical trial or “model programme” data. Although these studies could certainly be included in larger programmes, they are labour intensive and costly. For example, infants born to HIV infected mothers would have to be followed up for 15-18 months to rule out transmission. The care benefits of proper follow-up that accrue to mother and infant are substantial, so evaluation costs will be linked to service expenditures. Depending on venue and source of funding, ethical mandates to improve the standard of care for study participants would also reduce the generalisability of evaluations of enhanced prevention programmes and follow-up care. Thus, this type of evaluation would represent a best case scenario. Moreover, cohort studies will not yield data about the programme's coverage unless explicitly designed to do so.
One approach to measuring effectiveness is through anonymous screening of umbilical cord blood samples for HIV antibodies. Positive samples would then be tested for nevirapine (an indicator of maternal nevirapine coverage) using high performance liquid chromatography11
or the cheaper but less sensitive thin layer chromatography followed by high performance retesting of samples with negative results.20
Investigators in Zambia have used cord blood analysis combined with chart documentation of infants' receipt of nevirapine to measure true population coverage.11
When combined with patient level indicator data extracted from a woman's antenatal record at delivery, this approach provides an objective measure of effectiveness both for women who participated in the programme and in the broader population of women delivering in public labour wards.
Collection of patient data must be simplified and linked. In the absence of fully computerised, real time collection of patient health data,21
such linkage could be obtained by incorporating a small coded stamp into the medical record of women attending antenatal care (figure). A first generation of such a stamp was used when evaluating nevirapine coverage in pregnant women in Zambia22
and is being completed by health staff at each Zambian programme site during routine antenatal care and labour ward visits. The stamp provides a place to record important data for monitoring and evaluating prevention programmes. After delivery, the medical records are left in the health facilities' maternal and child health department, where the data can be readily entered on to computerised databases for analytical purposes or to aid clinic staff in postnatal outreach of infants born to HIV infected women.
Example of data collection stamp for use on antenatal care and labour records. Spaces shown represent where the dates of the given activity are recorded; multiple lines are provided for documentation of counselling or testing during follow-up visits. (more ...)
Use of a data stamp, combined with the umbilical cord blood analysis, permits collection of anonymous linked maternal and infant data—for example, by combining data on maternal programme indicators, maternal population drug coverage, and data on infant population drug coverage. This is crucial when attempting to identify shortcomings in the implementation of programmes and to estimate the proportion of children who will become infected with HIV. Moreover, inclusion of a modified version of the stamp in an infant's immunisation card may remind health staff of the need to test the infant for HIV and thereby improve postpartum follow-up rates (at least among those who return for immunisations).
The data stamps must be coded to protect the confidentiality of the mother and infant. Confidentiality can be violated only if a healthcare provider reveals the meaning of the stamp to a third party. This is analogous to a medical provider revealing the contents of a patient's medical record. In fact, a coded stamp would be more secure than standard medical record notes because it could not be interpreted without an explanation, whereas a third party might read records successfully without help. Nevertheless, before stamps are widely implemented we need pilot research to assess their feasibility and acceptability in a given clinical and cultural context.
We recognise that the above approach may be unsuitable for areas where a small proportion of women deliver in public labour wards (such as Haiti), where there is insufficient laboratory capacity to process and store cord blood specimens, and where programmes lack funds for high performance liquid chromatography analysis. The cost of analysing each specimen is around $50 (£25; €37),20
although high volumes should reduce costs. Nevertheless, a coded stamp could still enhance monitoring and evaluation efforts by allowing for simplified, periodic extraction of data. These data could verify the data presented in monthly monitoring reports and identify any shortfalls in the programme.
For programmes that use more complex antiretroviral regimens (such as short course zidovudine plus single dose nevirapine or nevirapine-containing highly active antiretroviral therapy), the absence of nevirapine in the cord blood would not necessarily imply a woman was not at least partly covered, assuming she adhered to the zidovudine portion of the regimen. Although zidovudine can be detected in cord blood,23
it is a less perfect surrogate for infant infection than nevirapine because it has a shorter half life and detection in the cord blood does not prove full compliance with the longer zidovudine regimen.
Other methods of measuring the effectiveness of these programmes have been reported. In South Africa, for example, facility based case finding approaches have been used to identify infants born to women accessing programme services,24
and mathematical modelling has also been used.25
However, these approaches do not separate each element of the prevention cascade, making it hard to pinpoint a programme's failures and successes.