Friday, October 28, 2011

Point of contact testing

In today's Lancet there is an article on point of Care (POC) testing in the context of HIV in Africa.

New durable, simple, and affordable cytometric CD4 testing devices aim to decrease the time to beginning antiretroviral therapy and loss to follow-up. Rapid testing with microfluidics meets the criteria for true POC testing, providing immediate results without needing laboratory personnel or infrastructure. These tests will conserve diagnostic resources and provide convenience and savings for patients. Whether the availability of such technology will help to overcome the many obstacles to successful delivery and scale-up of antiretroviral therapy in resource-limited settings is still to be shown.

CD4 staging establishes eligibility for antiretroviral therapy after HIV diagnosis. To obtain a CD4 cell count in resource-limited settings presents many challenges, and the scale of these challenges is often underestimated. The required two minimum clinic visits often span a month or longer, and associated transport costs can deter access to care. Pre-analysis infrastructure includes blood collection apparatus, a trained phlebotomist, and quick, reliable, and accountable transport and tracking of samples. Laboratories need functioning and calibrated instruments, trained and disciplined personnel, and quality assurance programmes. Finally, the return of CD4 results to a distant clinic is fraught with the difficulties of handwritten medical records and unique identifiers. POC testing offers a solution to many of these difficulties by dispensing with these multiple steps without compromising the accuracy of the result. But many of these difficulties are specific to rural Africa and cannot be extrapolated to downtown New York of even Cape Town.

The clinical settings in which POC CD4 testing might be most effective in treatment and retention have not been identified. Based on an observational study carried out in primary health clinics in Mozambique, Jani and colleagues report varied effects of POC CD4 testing on loss to follow-up at different points between enrolment and initiation of antiretroviral treatment. Decreased loss to follow-up was reported between enrolment and CD4 staging but not between CD4 staging and initiation of antiretroviral therapy in treatment-eligible patients. Time from enrolment to CD4 testing also decreased with POC testing, but this finding did not result in a difference in time to initiation of antiretroviral therapy after treatment eligibility was established. The largest loss, noted in many studies from Africa, occurs between rapid POC diagnosis of HIV infection and referral to a programme including CD4 testing. Efficiency could be improved through linkage of POC CD4 counts with HIV testing so that people who are HIV positive immediately receive CD4 testing, and targeted post-test counselling about risk of disease progression, transmission, and treatment eligibility. This approach might be particularly germane to programmes for the prevention of mother-to-child transmission of HIV, in which the time to initiation of antiretroviral therapy needs to be short for maximum benefit. In resource-limited settings, where late attendance to antenatal clinics is common, the need for urgent initiation of antiretroviral therapy in treatment-eligible pregnant women is even greater.

POC CD4 testing may not be ideal for every situation. In cities in Africa with well developed transportation and laboratory infrastructure, centralised, high-throughput flow-cytometry might be most efficient. At 20 min per sample, POC CD4 testing could rapidly overwhelm a busy clinic's capacity for patient throughput and service delivery. Conversely, POC capacity in rural clinics and mobile diagnostic services depends on sufficient demand to justify the expense of services in dispersed communities. The cost-effectiveness of placement of these units in voluntary counselling and testing for adults and antenatal clinics for prevention of mother-to-child transmission has not yet been tested, although the urgency of rapid initiation of antiretroviral treatment in eligible pregnant women is clearly of high importance for maternal health and transmission prevention. Feasibility and sustainability depend on the long-term durability of instruments; ease of maintenance, repairs, and replacements; availability of an adequate supply chain; and reasonable costs.

POC testing is a promising advance in efficient service delivery and monitoring in resource-limited settings. However, persistent, albeit lower, loss to follow-up occurs despite the introduction of this technology, which emphasises the complexity of health-seeking behaviour especially for HIV and acceptance of lifelong antiretroviral therapy. Successful HIV programmes should efficiently identify people with HIV by rapid testing, engage HIV-positive patients in care with rapid provision of CD4 staging, provide appropriate counselling, and assess readiness, then initiate antiretroviral therapy and retain individuals in care and treatment with appropriate monitoring. Although technology such as POC CD4 testing might improve service efficiency, such advances must be accompanied by increased knowledge about the barriers to retention, and implementation of solutions to prevent loss to follow-up, and to realise the full potential of HIV treatment, care, and prevention.

The AIDS epidemic has been the beneficiary of vast amounts of cash, no doubt driven by the homosexual lobby. Undoubtedly, the sciences of virology, immunology, gene therapy and molecular medicine have benefited from the attention paid to HIV. Point of Care testing has been an important issue in hematology. Anticoagulant control, diabetic control, pre-chemotherapy blood tests and even chemotherapy trough levels have been areas where POC testing might be thought to be beneficial. The drawback have always been expense and reliability. Reliable POC machines are very expensive and each individual measurement is slow. No doubt patients like them for their convenience, but money spent on them is money not spent elsewhere.

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