Currently, the majority of HIV-infected infants are found within limited-resource settings, where inadequate screening for HIV due to the lack of access to simple and affordable point-of-care tests impedes implementation of antiretroviral therapy. Here the authors report development of a low-cost dipstick p24 antigen assay using a visual readout format that can facilitate the diagnosis of HIV for infants in resource-poor conditions. A heat shock methodology was developed to optimize disruption of immune complexes present in the plasma of infected infants. The analytical sensitivity of the assay using recombinant p24 antigen is 50 pg/mL (2 pM) with whole virus detection as low as 42.5k RNA copies per millilitre plasma. In a blinded study comprising 51 archived infant samples from the Women and Infants Transmission Study, their assay demonstrated an overall sensitivity and specificity of 90% and 100%, respectively. In field evaluations of 389 fresh samples from South African infants, a sensitivity of 95% and specificity of 99% was achieved. The assay is simple to perform, requires minimal plasma volume (25 muL), and yields a result in less than 40 minutes making it ideal for implementation in resource-limited settings.
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Editors’ note: HIV This Week reported recently on the advantages of dried blood spot PCR testing for infant HIV diagnosis (http://hivthisweek.unaids.org/2009/11/26/diagnosis-and-monitoring). These authors take the field a step closer to rapid diagnosis – they take it to the field. They have developed a simple point of care test that circumvents the challenge of transporting specimens to a centralised laboratory and of finding the mother and her child when the result eventually returns. Results can be provided to parents at the same visit and plans made for the clinical evaluation of infants found to have HIV infection. The description of the test procedure seems quite straightforward, starting with a pre-treatment heat shock step to disrupt complexes that may have formed between maternal antibodies and infant HIV. The next step is develop a prototype portable, battery-powered heating/cooling unit and a prototype plasma separation device that would convert heel stick blood to plasma. Let’s hope that this next product development phase is rapid.
Currently, the majority of HIV-infected infants are found within limited-resource settings, where inadequate screening for HIV due to the lack of access to simple and affordable point-of-care tests impedes implementation of antiretroviral therapy. Here the authors report development of a low-cost dipstick p24 antigen assay using a visual readout format that can facilitate the diagnosis of HIV for infants in resource-poor conditions. A heat shock methodology was developed to optimize disruption of immune complexes present in the plasma of infected infants. The analytical sensitivity of the assay using recombinant p24 antigen is 50 pg/mL (2 pM) with whole virus detection as low as 42.5k RNA copies per millilitre plasma. In a blinded study comprising 51 archived infant samples from the Women and Infants Transmission Study, their assay demonstrated an overall sensitivity and specificity of 90% and 100%, respectively. In field evaluations of 389 fresh samples from South African infants, a sensitivity of 95% and specificity of 99% was achieved. The assay is simple to perform, requires minimal plasma volume (25 muL), and yields a result in less than 40 minutes making it ideal for implementation in resource-limited settings.
HIV This Week reported recently on the advantages of dried blood spot PCR testing for infant HIV . These authors take the field a step closer to rapid diagnosis – they take it to the field. They have developed a simple point of care test that circumvents the challenge of transporting specimens to a centralised laboratory and of finding the mother and her child when the result eventually returns. Results can be provided to parents at the same visit and plans made for the clinical evaluation of infants found to have HIV infection. The description of the test procedure seems quite straightforward, starting with a pre-treatment heat shock step to disrupt complexes that may have formed between maternal antibodies and infant HIV. The next step is develop a prototype portable, battery-powered heating/cooling unit and a prototype plasma separation device that would convert heel stick blood to plasma. Let’s hope that this next product development phase is rapid.
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