Your search found 4 Results

  1. 1
    Peer Reviewed

    Designing HIV testing algorithms based on 2015 WHO guidelines using data from six sites in sub-Saharan Africa.

    Kosack CS; Shanks L; Beelaert G; Benson T; Savane A; Nganga A; Bita A; Zahinda JP; Fransen K; Page AL

    Journal of Clinical Microbiology. 2017 Oct; 55(10):3006-3015.

    Our objective was to evaluate the performance of HIV testing algorithms based on WHO recommendations, using data from specimens collected at six HIV testing and counseling sites in sub-Saharan Africa (Conakry, Guinea; Kitgum and Arua, Uganda; Homa Bay, Kenya; Douala, Cameroon; Baraka, Democratic Republic of Congo). A total of 2,780 samples, including 1,306 HIV-positive samples, were included in the analysis. HIV testing algorithms were designed using Determine as a first test. Second and third rapid diagnostic tests (RDTs) were selected based on site-specific performance, adhering where possible to the WHO-recommended minimum requirements of 99% sensitivity and specificity. The threshold for specificity was reduced to 98% or 96% if necessary. We also simulated algorithms consisting of one RDT followed by a simple confirmatory assay. The positive predictive values (PPV) of the simulated algorithms ranged from 75.8% to 100% using strategies recommended for high-prevalence settings, 98.7% to 100% using strategies recommended for lowprevalence settings, and 98.1% to 100% using a rapid test followed by a simple confirmatory assay. Although we were able to design algorithms that met the recommended PPV of 99% in five of six sites using the applicable high-prevalence strategy, options were often very limited due to suboptimal performance of individual RDTs and to shared falsely reactive results. These results underscore the impact of the sequence of HIV tests and of shared false-reactivity data on algorithm performance. Where it is not possible to identify tests that meet WHO-recommended specifications, the low-prevalence strategy may be more suitable.
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  2. 2
    Peer Reviewed

    Evaluation of two staging systems for HIV infection for use in developing countries.

    Vandenbruaene M; Colebunders R; Goeman J; Alary M; Farber CM; Kestens L; Van Ham G; Van den Ende J; Van Gompel A; Van den Enden E

    AIDS. 1993 Dec; 7(12):1613-5.

    In 1990, Belgium, physicians enrolled 415 consecutive patients attending HIV reference centers in Antwerp, Brussels, and Ghent in a cross-sectional study designed to evaluate the clinical axis of the WHO staging system with and without the lymphocyte stratification proposed by Montaner el al. (that is, modified WHO staging system) (>1500, 1500- 1000, and <1000 cells x 1 million/l). They filled in a standardized questionnaire with all criteria of the WHO staging system. Laboratory personnel used standard hematology and flow cytometry techniques to determine absolute and CD4 lymphocyte counts. 80% of the patients were Caucasians. 46% of all patients were homosexual and 42% were heterosexual; 79.2% were men. Median CD4 lymphocyte counts fell in both staging systems as the stage of HIV infection increased. There were significant differences in median CD4 counts between stages of each staging system (p < .001). The modified WHO staging system's stage I was more sensitive at identifying patients with CD4 lymphocyte counts of more than 500 cells x 1 million/l than the WHO clinical stage 1 (83% sensitivity vs. 48% sensitivity). The positive predictive value of WHO clinical stage 4 and of the modified WHO staging system's stage IV for identifying people with CD4 lymphocyte counts of less than 200 cells x 1 million/l was quite high (79% and 80%, respectively). The researchers suggested that clinicians use stages 4 and IV as end-points is clinical trials in developing countries. Clinicians completing the questionnaire knew the patients' earlier CD4 lymphocyte count, which may have introduced a bias in the study. For example, they may have more thoroughly examined patients with low CD4 lymphocyte counts than those with normal counts. Nevertheless, the study's results indicated that either one of these systems may be a good alternative in developing countries to the technical equipment-dependent CD4 lymphocyte count-based HIV staging system used in developed countries. Cohort studies in developing countries would evaluate their prognostic value.
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  3. 3

    HIV testing: reduce costs by all means, but not at all costs [letter]

    Simon F; Brun-Vezinet F

    Lancet. 1993 Aug 7; 342(8867):379-80.

    Some HIV specialists propose alternative strategies of anti-HIV antibody screening to reduce costs. A western blot (WB) test confirming a positive anti-HIV antibody screening test is the time-honored strategy. WHO has guidelines on how to interpret WB results and how to handle indeterminate patterns. Tests for p24 antigen may identify HIV infection in those cases where the WB test fails to detect HIV infection during seroconversion. Alternative strategies proposed by authors of an earlier article to reduce HIV testing costs are flawed. For example, in 1 strategy, a positive result in the first test or ELISA and a negative result in a second test based on antigens or in another screening test based on a different principle leads to medical workers telling the person that he/she is HIV seronegative. Yet, the negative results of the second test may be due to seroconversion. Even though the first test should be as sensitive as possible, a subsequent negative test result should require another blood sample to test for p24 antigen. A second proposed strategy uses a competitive ELISA as the second test, but these assays cannot detect HIV-2 infection. The authors pooled the samples to illustrate cost saving, but pooling data loses sensitivity, especially for rapid tests. Virologists from Hospital Bichat-Claude Bernard in Paris, France, and earlier demonstrated the loss of sensitivity of rapid tests among sera from 9 patients in the early stage of HIV-1 seroconversion. They further believed that the manufacturer should determine reliability, sensitivity, and specificity. WHO did not take the above information into account when it addressed reducing the costs of HIV screening tests. Realistic diagnostic strategies are indeed needed in countries with few resources, but unreliable testing should not be the result of cost reductions.
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  4. 4

    Clinical case definition for AIDS in Africa [letter]

    Jackman J; Hedderwick S

    Lancet. 1990 Jun 16; 335(8703):1456-7.

    The aim of the World Health Organization (WHO) clinical case definition of pediatric acquired immunodeficiency syndrome (AIDS) in Africa was to provide a noninvasive means of diagnosing AIDS without serology. Although this definition has been evaluated in terms of its sensitivity and specificity, little attention has been given to its ease of application. A review of 65 pediatric inpatient admissions in Uganda's Kisiizi Hospital indicated that there are, indeed, difficulties in applying the WHO clinical case definition. For example, the definition requires parents to have detailed knowledge of their child's rate of growth. Not only are parents unable to report their child's weight, but centile charts used at child health centers are rarely kept up to date. Moreover, in Uganda, where there is a shortage of hospital beds, parents tend to exaggerate their child's symptoms to gain admission--a tendency that produces a high rate of false-positive AIDS diagnoses. Confirmed maternal human immunodeficiency virus (HIV) infection was also impossible to document, both because of a lack of serologic screening capability and social stigma against acknowledging seropositivity. Finally, language difficulties compounded parent-physician communication.
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