HIV :: UNAIDS comment on population-based study in south India

UNAIDS welcomes the report published in BioMed Central Medicine concerning a large and high-quality study in the Guntur district in the south Indian state of Andhra Pradesh. It contributes to a better understanding of the distribution of HIV in India?s enormous and diverse population although it is based on just one district.

However, UNAIDS is concerned about some of the extrapolations and calculations in the paper. Prevalence measured in a household survey is expected to be close to the true prevalence in areas with relatively high prevalence (as in Guntur district where the study was conducted). However, it also underestimates the true prevalence in areas with lower prevalence (as in many of the northern states in India). Prevalence levels and epidemic dynamics vary considerably across different states in India.

Therefore, the interpretation of the comparison of the Guntur survey prevalence with an estimate for Guntur District based on the India National AIDS Control Organization?s (NACO) method should not be extended to the whole of India.

While the study in Guntur indicates that the true HIV prevalence in that district is lower than that observed among antenatal clinic attendees, other studies in the south Indian states of Tamil Nadu and Karnataka (also areas with relatively high HIV prevalence) suggest that the prevalence among the general adult population is similar to that observed among antenatal clinic attendees.

The paper used an ANC prevalence of 3% for Guntur district to apply the NACO method. However, NACO does not estimate HIV prevalence by district, but by state, grouping them by level of HIV prevalence. The average prevalence among ANC attendees for the state of Andhra Pradesh was 2%, lower than the 3% used in the current paper for the Guntur district.

For these reasons, we believe that the UNAIDS/WHO national estimate of 0.9% (0.5-1.5%) reflects the best current estimate of prevalence for India. This estimate acknowledges considerable uncertainty, recognizing that it is derived from sentinel surveillance data and assumptions about the representativeness of that data.

Although the current study has great value, UNAIDS feels that the results of a 2006 national survey in India (NFHS-3, results are expected in the first quarter of 2007) will allow for a better appreciation of the true level of HIV prevalence in India, compared to extrapolations based on findings of one study in a small area. UNAIDS and WHO are committed to working with NACO and its partners in India in revising the estimate for India when the information from the national survey becomes available.

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