Has HIV Prevalence Peaked in South Africa?–can the Report on the Latest Antenatal Survey be Trusted to Answer This Question? (Commentary) (Survey)
On the weekend of Friday 29 August, the National Department of Health placed their report on the results of the 2007 national antenatal survey, carried out a little over 10 months ago, on their website. (1) The Department uses these results (showing an overall HIV prevalence of 28%) to reinforce those of the previous survey (2) and argue that ‘South Africa may be making some real progress in its response to the HIV epidemic’ and that the ‘South African HIV epidemic is on a downward trend’. While this may or may not be true, in order for one to infer a trend in indicators from a sequence of surveys they need to be comparable, year on year, with one another. Unfortunately this is not the case with the antenatal surveys of the past 2 years. In 2006 the survey sample was doubled in size and the sentinel sites chosen on the probability proportional to size (PPS) basis designed, as pointed out in the most recent report, (1) to provide (for the first time) prevalence estimates for each district in the country on a self-weighting sample. Compared with the national prevalence of 30.2% reported for 2005, it was argued that the 29.1% in 2006 suggested that ‘for the first time that the South African epidemic may be beginning a downward trend’. (2) However, as the 2006 survey sample was so different from that used previously, one cannot be sure of the extent to which the decrease is due simply to the larger, more representative survey measuring prevalence more accurately. Although there is mounting evidence of a fall in prevalence among young pregnant women, one cannot interpret the overall trend without a thorough analysis of the data, which unfortunately are not in the public domain.