Detection of Recent Human Immunodeficiency Virus Type 1 (Hiv-1) Infections and Estimating Its Incidence Rate in Ethiopia.
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Date
2007-07
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Addis Ababa University
Abstract
Several tests have been developed to diagnose HIV/AIDS and detect the presence of anti-HIV-1
antibodies. But, these tests were not able to distinguish recent from established infections which
are particularly useful in estimating the incidence of HIV-1. Recently, a simple enzyme
immunoassay was developed that detects increasing levels of anti-HIV IgG after seroconversion
and can be used for detecting recent HIV-1 infections to estimate incidence. This involves use of
the branched peptide that includes gp41 immunodominant sequences from HIV-1 subtypes B, E
and D allowing detection of HIV specific antibodies among various subtypes including the HIV-1
subtype C, which is accountable for the intense epidemic observed in Ethiopia. Therefore, the
objective of this study was to use this assay to detect recent infections and estimate HIV-1
incidence rates among five regions (Addis Ababa, Tigray, SNNPR, Oromia, and Amhara),
specific areas (urban and rural) of these regions and make comparison of HIV-1 incidence rates
among different age groups in the selected regions by using cross sectional samples collected
from pregnant women who attended Antenatal Care Clinics in the 2005 HIV surveillance in
Ethiopia. However, some specimens from persons with longer-term infection could be classified
as recent by the assay and this can inflate the incidence estimate. Thus, the incidence estimate
was adjusted for misclassifications by using a recently developed formula. The adjustment for
misclassification is a dynamic formula correcting for the imputed sensitivity and specificity of the
assay based on the analysis of specimens with known dates of seroconversion and maintained the
incidence estimate closer to the observed incidence. As a result, the study showed a national
adjusted incidence rate of 2.05% (95% CI, 1.83-2.26) in pregnant women aged 15-49 (urban
3.13% (95% CI, 2.71-3.55) and rural 1.24% (95% CI,1.00-1.46)). The highest proportion of
recent infections (P<0.05) and the largest incidence of HIV-1 (8.4%) (95% CI, 6.13-10.14) was
observed in Addis Ababa, the capital city. The lowest incidence of HIV-1 was observed in
SNNPR. Overall, higher proportion of recent infections was detected in rural health centers
(26.8%) as compared to the urban (22.2%), (P > 0.05). Incidence of HIV-1 was found to be
higher in the urban areas except for Amhara where the reverse was true. Age wise the highest
proportion of recent infections was detected in the age group between 15-19 years (32.2%)
(P<0.05) with the highest incidence being in the age group 25-29 years (2.33%) (95% CI, 1.90-
2.76). In conclusion, the BED HIV-1 incidence assay provides a valuable tool in obtaining
information about recent infection and incidence of HIV -1 and thus can be useful for purposes
such as the identification of high risk population for enrolling in studies or intervention of early
infection. The incidence estimate in the present study can only be considered as relevant for the
five regions, not for the whole of Ethiopia because sampling strategy is limited to five regions
(Addis Ababa, Tigray, SNNPR, Oromia, and Amhara) which account for the majority of HIV
prevalence in Ethiopia and specimens obtained through similar sampling strategies should be
used to compare the results obtained by using this assay with those reported by the Ministry of
Health.
Keywords: AIDS , Antenatal care clinics , Assay , BED-HIV-1 incidence assay , Ethiopia , gp41,
HIV-1 , IgG , Incidence , Misclassifications , Recent infections , Seroconversion
Description
Keywords
AIDS, Antenatal care clinics, Assay, BED-HIV-1 incidence assay, Ethiopia ;gp41;HIV-1 ;IgG ; Incidence, Misclassifications, Recent infections, Seroconversion