A model for CD4 point-of- care testing was unveiled at last month’s International Aids Conference in Vienna, Austria.
The instrument, which looks similar to a thermometer and is 5cm long, the size of a pen cap, allows for rapid results and similar accuracy to tests conducted in a laboratory, but involves less technical equipment, significantly reduced cost and fewer personnel. The high price and complicated technology of current CD4 testing makes its implementation difficult in places with limited resources, particularly throughout Southern Africa, the area in which the virus has had the greatest impact.
Steven Reid of Imperial College London, who managed the project, described the benefits of the new device in comparison to traditional forms of diagnostics as follows: “[Current] CD4 testing is done in a really large laboratory and in a big hospital. It’s a huge machine, it has lasers and it needs daily maintenance, quality control and dedicated personnel. Storage and equipment is expensive. The patient needs to come twice, once to give a blood sample and once to get a result,” he said, noting that patients often don’t return in rural areas where transportation is scarce. “The benefit of a point-of-care test is that the patient can get a result right away, right there. We’ve simplified the entire mechanism.”
CD4 testing is vital for people living with HIV, as it measures the status of the immune system and helps determine when treatment should begin. The World Health Organisation recommends starting treatment when the CD4 count drops below 350, but many African countries set this number at 200. Without accurate CD4 testing, many patients do not begin treatment until they are very sick, limiting their possibility of survival.
Whereas current CD4 testing requires blood to be drawn and analysed by highly trained technicians by means of an expensive, desk-size machine, the point-of-care device requires only a pinprick of blood, limited technical skill and no refrigeration, offering results within 10 minutes. Created by United States-based company Zyomyx, the test works by using a reagent that binds to CD4 cells, making them heavier than other components of the blood and sinking them to the bottom of the device.
The result is then read like a thermometer. Although the final product has yet to be produced, its accuracy will be compared with the CD4 laboratory test, said the company’s chief executive, Peter Wagner. “We have to be equally good. People need to rely on the result and so it will have the same accuracy and precision as the gold standard,” he said. Although it hasn’t been tested in the field yet, “already, this precision has been proved [by Zyomyx] and by Imperial College”, Wagner said.
The disposable test will be used by nurses and other healthcare professionals, primarily in rural settings where laboratories are virtually nonexistent. The idea of a point-of-care test was born in 2000, when Aids activist Gregg Gonsalves visited Southern Africa and noted problems with the high cost, long waiting times and limited accessibility stemming from laboratory-based diagnostics. Because of the traditional test’s large size and cost, attempting to put the machines in a small clinic in Malawi or Lesotho was “ludicrous”, Gonsalves said.
Furthermore, although drug costs were dropping, the cost and complexity of diagnostic technology remained high. “Diagnost ic moni toring was fast going to outstrip the cost of treatment,” he said. After speaking to Mèdicins sans Frontières in Khayelitsha, scientists and other service providers, Gonsalves concluded that they were faced with a significant problem. “We needed a test that was really fast, simple, cheap, that could run without much training at all and definitely no electrical equipment.”
The team secured $16-billion from the Bill & Melinda Gates Foundation, with Imperial College overseeing the project and soliciting applications from potential companies. Although six projects were funded initially, only those that were successful had their funding renewed. Four years later Zyomyx’s thermometer-like device was the only to remain.
Reid said the use of an industry-based model was central to the success of the project. ‘In the case of traditional academic funding, you give a grant for several years,” he said. “We asked: ‘What about the product?’ We couldn’t risk handing over that much money and we needed appropriate stewardship of the money. We took a lot of industrial methods and put it into this public-private partnership.”
According to Wagner, Western-based companies often make products for developed countries, hoping to alter them later for use in developing settings. “When other companies try to tweak
for other markets, they fail miserably,” he said. “This product, on the other hand, was made specifically to bring [testing] to low-income areas.”
The project management offered by Imperial College helped expedite the process. “This model was actually produced faster than would have been possible in a company because there has been such indepth involvement in it,” said Reid. “Even the best people in the world drift off into other tangents and sometimes you need someone to streamline the project.”
The device has undergone preliminary testing in London, with field testing to be conducted in the next few months to ascertain its use in low-resource and rural areas. Wagner expected the instrument to be finalised and made available in two years. Although its cost has yet to be set,
Reid estimated it will be $2 to $3 a test. But, in spite of the initial excitement, Gonsalves was worried that the push to finalise the device may not be met with adequate funding.
“The challenge now is that it still needs a year or so of fine-tuning and optimisation before it can go out into the field. It’s not clear that a funder is going to come up with the other $2-million to $3-million to finish the job,” he said. “This device is something you would never expect, it’s beyond our wildest dreams. It’s strange that, with such a promising technology that really could revolutionise Aids care, we’re worried about seeing it through to the end.”