Abstracts

Estimates of HIV incidence rates are important for evaluating the epidemic’s dynamics, targeting the implementation of appropriate preventive measures, monitoring intervention strategies and highlighting the impact of the virus infectivity and its transmission ¹1 Morgado MG, Bastos FI. Estimates of HIV-1 incidence based on serological methods: a brief methodological review. Cad Saúde Pública 2011; 27 Suppl 1:S7-18.. According to the Brazilian Ministry of Health ²2 Programa Nacional de DST-AIDS, Ministério da Saúde. Boletim Epidemiológico de AIDS e DST 2013; ano VII, nº 1., most cases of HIV-positive pregnant women were reported in the Southeast (43%) and South regions (32%), followed by the Northeast region (14%). An important point for the evaluation of HIV-positive pregnant women is the possibility of mother-to-child transmission ³3 Rodrigues R, Manenti S, Romao PR, de Paula Ferreira JL, Batista JP, Siqueira AF, et al. Young pregnant women living with HIV/AIDS in Criciuma, Southern Brazil, are infected almost exclusively with HIV type 1 clade C. AIDS Res Hum Retroviruses 2010; 26:352-7..

Surveillance of the epidemic through the counting of AIDS cases does not reflect the current epidemic dynamics. For this reason, we decided to apply for the first time in the Northeast of Brazil a methodology that uses laboratory assays for the identification of a period of recent seroconversion and estimates HIV-1 incidence, known as RITA (Recent Infection Testing Algorithm) ⁴4 UNAIDS Working Group on Global HIV/AIDS and STI Survaillance. When and how to use asssays for recent infection to estimate HIV incidence at a population level. Geneva: World Health Organization; 2011..

The study aimed to determine HIV-1 incidence through immunoassays among individuals attending at the Voluntary Counseling and Testing Center (VCT) in Paulista, city in the Metropolitan Region of Recife, Pernambuco State, Northeast Brazil, in the period from 2006 to 2009. The VCT treated a total of 14,014 individuals, including 5,949 pregnant women, 4,418 non-pregnant females and 4,092 male individuals in that period. Patients arrived at the VCT as a result of being sent by Primary Healthcare Units or through spontaneous demand.

HIV-1 diagnosis was performed according to the guidelines of the Brazilian Ministry of Health. To exclude the possibility of false recent infection results, the following were excluded: individuals who had previously used antiretroviral therapy (ART), those who reported mother-to-child transmission, and those with previous HIV-1 diagnosis detected more than six months from the date of collection of the research sample. These aspects were evaluated by observing the registration of individuals in HIV/AIDS healthcare programs or at medical records of the Central Public Health Laboratory of Pernambuco. Demographic characteristics data were retrieved from medical records at the VCT-Paulista.

A BED-capture enzyme immunoassay (BED-CEIA) was used for HIV-1 incidence (Calypte Biomedical Corporation, Portland, USA) ⁵5 Parekh BS, Kennedy MS, Dobbs T, Pau, C, Byers R, Green T, et al. Quantitative detection of increasing HIV type 1 antibodies after seroconversion: a simple assay for detection recent HIV infection and estimating incidence. AIDS Res Hum Retroviruses 2002; 18:295-307.. Incidence calculations and 95% confidence intervals were performed with the spreadsheet provided by the South African Centre for Epidemiological Modeling and Analysis (SACEMA; http://www.incidence-estimation.com/page/tools-for-incidence-from-biomarkers-for-recent-infection) ⁶6 Kassanjee R, McWalter TA, Bärnighausen T, Welte A. A new general biomarker-based incidence estimator. Epidemiology 2012; 23:721-8.. The incidence rate was estimated as 100 people per year and presented as a percentage. In addition, samples were tested for another recent HIV infection assay, the Avidity Index AxSYM method (Ax-AI), performed as described previously ⁷7 Suligoi B, Galli C, Massi M, Di Sora F, Sciandra M, Pezzotti P, et al. Precision and accuracy of a procedure for detecting recent human immunodeficiency virus infections by calculating the antibody avidity index by an automated immunoassay-based method. J Clin Microbiol 2002; 40:4015-20.. All samples were stored at minus 70ºC. We examined associations between groups using the Pearson’s chi-square test and kappa test to evaluate the degree of agreement between diagnostic assays. The study was approved by the Ethics Research Committee of Agamenon Magalhães Hospital, under registry number 429/2009, in accordance with Brazilian norms for research involving human subjects.

A total of 14,014 individuals were tested serologically for HIV-1, most of whom were women (n = 9,912; 70.8%), and pregnant women comprised a total of 5,494 persons. In this study, 167 were diagnosed with HIV-1, among whom sociodemographic and behavioral characteristics were obtained for 159 of them (Table 1). Most HIV-positive individuals were male (54.1%) and heterosexual (78.6%).

We observed a prevalence of 1.18% (95%CI: 1.01-1.37) and incidence of 0.50% per year (95%CI: 0.27-0.73) (Table 2). The prevalence for HIV-1 infection in pregnant women (0.33%; 95%CI: 0.19-0.52) was significantly lower than that observed in men (2.25%; 95%CI: 1.82-2.75) and non-pregnant women (1.29%; 95%CI: 0.98-1.67; p < 0.000001). Although the rate of recent infection was around 20% in all study groups, pregnant women had lower incidence rates (0.15% per year; 95%CI: 0.00-0.33) than non-pregnant women (0.50% per year; 95%CI: 0.11-0.89; p = 0.0015) and men (1.03% per year; 95% CI: 0.45-1.61, p < 0.000001). There are few HIV incidence estimates by serological methods in Brazil; however, it has been demonstrated that in the South and Southeast of the country there are usually higher rates, such as 2.86% (95%CI: 1.04-4.68) in the South ⁸8 Ferreira JLP, Thomaz M, Rodrigues R, Harrad D, Oliveira CM, Oliveira CAF, et al. Molecular characterisation of newly identified HIV-1 infections in Curitiba, Brazil: prepoderance of clade C among males with recente infections. Mem Inst Oswaldo Cruz 2008; 103:800-8. and between 1.2-2.7% for men and 0.6-1.2% for women in the Southeast ⁹9 Alves KA, Shafer KP, Caseiro M, Rutherford G, Falcao ME, Sucupira MC, et al. Risk factors for incident HIV infection among anonymous HIV testing site clients in Santos, Brazil: 1996-1999. J Acquir Immune Defic Syndr 2003; 32:551-9.^,1010 Merçon M, Tuboi SH, Batista SM, Telles SRB, Grangeiro JR, Zaddenverg R, et al. Risk-based assessment does not distinguish between recent and chronic HIV-1 infection in Rio de Janeiro, Brasil. Braz J Infect Dis 2009; 13:272-5.. We should emphasize that we did not have enough data to determine HIV-1 incidence and prevalence among men who have sex with men (MSM), and as demonstrated by Merçon et al. ¹⁰10 Merçon M, Tuboi SH, Batista SM, Telles SRB, Grangeiro JR, Zaddenverg R, et al. Risk-based assessment does not distinguish between recent and chronic HIV-1 infection in Rio de Janeiro, Brasil. Braz J Infect Dis 2009; 13:272-5., in Rio de Janeiro, the incidence in this group was five times higher than in heterosexual men, supposing that the presence of MSM may have inflated HIV-1 incidence and prevalence estimates among males.

We tested samples with Ax-AI assay for comparison with BED-CEIA. A higher correlation between the tests was observed in the group of pregnant women (kappa = 0.82), in which only 01/18 samples showed different results. The group of non-pregnant women showed a greater divergence between tests (kappa = 0.43), while for males a kappa of 0.69 was obtained.

One advantage of this work is data from two different methodologies for detection of recent HIV infection, the BED-CEIA and Ax-AI. These assays differ in the kinds of antigens and techniques, which increase the specificity for detecting recent infections. We demonstrate an excellent correlation between the results of the BED-CEIA and Ax-AI among pregnant women, therefore the changes in response to anti-HIV antibodies occurring during pregnancy are not sufficient to interfere with the results of these assays ¹¹11 Laeyendecker O, Church JD, Oliver AE, Mwatha A, Owen SM, Donnell D, et al. Pregnancy does not affect HIV incidence test results obtained using the BED capture enzyme immunoassay or an antibody avidity assay. PLoS One 2010; 5:e13259.. Although serological assays have reasonable sensitivity to detect recent HIV infections, one disadvantage of the study is the absence of other laboratory markers for more accurate incidence estimates, such as the CD4+ T lymphocyte count, HIV-RNA detection and quantification of viral load, as well as data on the time interval between the last negative and the first positive HIV serological assay at multi-tested patients.

This is the first study reporting the HIV-1 incidence among pregnant women using a serological strategy in Northeast Brazil. We found an incidence rate of 0.15% per year in pregnant women, very similar to that determined in São Paulo (0.2% per year) ¹²12 Oliveira CAF, Ueda M, Yamashiro R, Rodrigues R, Sheppard HW, Brígido LFM. Rate and incidence estimates of recent human immunodeficiency virus type 1 infections among pregnant women In São Paulo, Brazil, from 1991 to 2002. J Clin Microbiol 2005; 43:1439-42.. Higher incidence estimates were observed in Rio de Janeiro (0.41%; 95%CI: 0.11-0.72) and Rio Grande do Sul (1.93%; 95%CI: 0.88-2.97) ¹1 Morgado MG, Bastos FI. Estimates of HIV-1 incidence based on serological methods: a brief methodological review. Cad Saúde Pública 2011; 27 Suppl 1:S7-18.. A HIV-1 incidence estimate of 0.61 per 1,000 persons-years was found in Central Brazil, smaller than our estimates ¹³13 Costa ZB, Stefani MMA, Lima YAR, Souza WV, Filha NTS, Turchi MD, et al. Estimates incidence and genotypes of HIV-1 among pregnant women in Central Brazil. PLoS One 2013; 8:e79189..

HIV-1 prevalence was significantly higher among males. Although the HIV epidemic is concentrated in MSM in the Recife metropolitan area ¹⁴14 Cavalcanti AMS, Brito AM, Salustiano DM, Lima KO, Silva SP, Lacerda HR. Recent HIV infection rates among HIV positive patients seeking voluntary counseling and testing centers in the metropolitan region of Recife – PE, Brazil. Braz J Infect Dis 2012; 16:157-63., there is an increase in the rate of HIV infection in pregnant women since 2000 ²2 Programa Nacional de DST-AIDS, Ministério da Saúde. Boletim Epidemiológico de AIDS e DST 2013; ano VII, nº 1.. An appropriate preventive or health intervention must be implemented to prevent the spread of the virus among pregnant women and their partners.

Paulista is part of the metropolitan region of Recife. Its proximity (17km) to the state capital, Recife, means there are significant population flows between the two cities. Data from incidence by serologic methods have been recommended for epidemiological studies because they provide real observations about the current epidemic. Our data demonstrate the large difference between the HIV-1 prevalence and incidence rates in different populations and the importance of serological testing for HIV during antenatal care, where we see a high rate of recent infection, so we assume that a significant proportion of pregnant women were infected at a time close to or during pregnancy.

Acknowledgements

We thank all the staff of VCT-Paulista.

References

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