Accuracy of serological assays for detection of recent infection with HIV and estimation of population incidence: a systematic review.

We systematically reviewed the accuracy of serological tests for recent infections with HIV that have become widely used for measuring population patterns incidence of HIV. Across 13 different assays, sensitivity to detect recent infections ranged from 42-100% (median 89%). Specificity for detecting established infections was between 49.5% and 100% (median 86.8%) and was higher for infections of durations longer than 1 year (median 98%, range 31.5-100.0). For four different assays, comparisons were made between assay-derived population incidence estimates and a reference incidence estimate. The median percentage difference between the assay-derived incidence and reference incidence was 26.0%. Serological assays have reasonable sensitivity for the detection of recent infection with HIV, but are vulnerable to misclassifying established infections as recent-potentially leading to biases in incidence estimates. This conclusion is highly qualified by the apparent absence of a standardised approach to assay evaluation. There is an urgent need for an internationally agreed framework for evaluating and comparing these tests.

Lessons learned in the conduct, validation, and interpretation of national population based HIV surveys.

In the past few years several countries have conducted national population-based HIV surveys. Survey methods, levels of participation bias from absence or refusal and lessons learned conducting such surveys are compared in four national population surveys: Mali, Kenya, Peru and Zambia. In Mali, Zambia, and Kenya, HIV testing of adult women and men was included in the national-level demographic and health surveys carried out regularly in these countries, whereas in Peru the national HIV survey targeted young people in 24 cities with populations over 50 000.The household response rate was above 90% in all countries, but some individuals were absent for interviews. HIV testing rates were between 70 and 79% of those eligible, with higher test rates for women. Three critical questions in this type of survey need to be answered: who did the surveys miss; how much it matters that they were missed; and what can be done to increase the participation of respondents so the coverage rates are adequate. The level of representativeness of the populations tested was adequate in each survey to provide a reliable national estimate of HIV prevalence that complements other methods of HIV surveillance. Different lessons were learned from each survey. These population-based HIV seroprevalence surveys demonstrate that reliable and useful results can be obtained, although they require careful planning and increased financial and human resource investment to maximize responses at the household and individual level, which are key elements to validate survey results.This review was initiated through an international meeting on 'New strategies for HIV/AIDS Surveillance in Resource-constrained Countries' held in Addis Ababa on 26-30 January 2004 to share and develop recommendations to guide future surveys.

Status of the HIV/AIDS epidemic and methods to monitor it in the Latin America and Caribbean region.

The paper presented is a review of the available epidemiological data on the situation in the Latin America and Caribbean (LAC) region, and looks at HIV prevalence in specific population groups. At the end of 2001, HIV remains an important health issue in the LAC region. Twelve countries in the region have an estimated prevalence of 1% or higher among pregnant women. Most of the LAC countries with generalized epidemics are located in the Caribbean basin. In the past decade there has been a slow but continuous increase in HIV prevalence rates among the general population and vulnerable groups, although information in some countries is limited. In many countries, the highest HIV prevalence among vulnerable groups is found among men who have sex with men. HIV infections related to injecting drug use are concentrated in the countries of the Southern Cone and Brazil. HIV is well anchored in the region, concentrated in vulnerable groups in most countries, but with an increasing presence in some countries in the general population. There is a need to improve data collection and introduce new tools to monitor behavior trends and the impact of interventions.