Paper test for safer drug treatment
RESEARCHERS LOOKING to make tuberculosis (TB) and HIV treatment safer have developed a paper-based test for drug-induced liver damage. Standard treatments for TB such as rifampicin and pyrazinamide can cause liver damage, particularly in people co-infected with hepatitis B or C, which are common in Asia. Similarly, patients can experience liver damage if they are treated for HIV with commonly used nevirapine-based drugs. Yet clinicians in developing countries rarely have easy access to tests for drug-induced liver injury, said Nira Pollock, assistant professor of medicine at Harvard Medical School in the United States. US doctors routinely check for high levels of chemical markers in blood that show if patients are developing serious liver damage, and then adjust their medication accordingly. Now, researchers have developed and tested a stamp-sized paper device with channels and wells that mix, split and filter a finger-prick blood sample to detect these chemical markers. The trial used existing blood samples to compare the device to standard tests. It showed an overall accuracy of more than 90 per cent compared with the gold standard of 100 per cent. It takes just 15 minutes to get the colour changes that indicate normal, moderate or high levels of liver markers. The test also includes a control that confirms the test was accurate. The estimated cost of each test is just ten US cents, compared with upfront costs of thousands of dollars for existing point-of-care mini laboratory devices. Jason Rolland, senior director of research from Diagnostics For All, which developed the technology, said the test is cheap, easy to use, and portable, with no need for electricity or instrumentation. “It is designed to be used in a rural clinic to support our mission in the developing world,” he added. Usually liver function testing for patients in rural areas requires samples to be sent to large hospitals, and they can get lost en route, said Rolland. He added that drug-induced liver damage rates are between ten and 25 per cent in the developing world, compared to around two per cent of patients being treated for TB in the developed world. Pollock coordinated the trial and is liaising with the National Hospital for Tropical Diseases in Vietnam to conduct field trials of the device in patients suffering from HIV. If the test works as well in patients, the researchers are hoping to have a commercial product in 2014. Currently, Diagnostics for All is able to manufacture 500 to 1,000 tests per day. Commenting on the research, Alison Grant, assistant professor of medicine at the London School of Hygiene and Tropical Medicine, said the technology “could be very useful for patients at high risk or thought to have liver damage”. But she cautioned that not all patients benefit from routine liver function testing, and WHO guidelines recommend it only for patients at highest risk. And the cost could be higher than stated. “Experience of other point-of-care tests suggests that in addition to initial training, staff need refresher training periodically to be sure they are using the test correctly, and this support needs to be taken into account when estimating the true cost of the test,” Grant added. (SciDEV)
‘Electronic nose’ to detect TB
SCIENTISTS FROM Bangladesh and the Netherlands have proven the efficiency of an electronic diagnostic device that detects tuberculosis (TB) of the lung. The device, named electronic nose (eNose), can obviate cumbersome conventional diagnosis where patients’ sputum is examined under the microscope, cultured in a laboratory and lung X-rays taken to confirm infection. Pilot studies, done in collaboration with Bangladesh’s National TB Control Programme and lasting seven months until September 2009, proved the new device to be simple, rapid, highly sensitive and specific. The findings have been reported in Tuberculosis Journal. About 230 subjects, both healthy and active TB germ carriers, were involved in the studies. “This is a revolutionary invention which will give significant advantage to users in places with a high TB infection burden like Bangladesh,” said Zeaur Rahim, a scientist who led the studies at the International Centre for Diarrhoeal Disease Research, Bangladesh. “Since there is no direct handling of patients’ biological samples, the device allows risk-free diagnosis,” Rahim said. The device scores on accuracy and early diagnosis which are essential to controlling pulmonary TB in countries with high TB prevalence. Sputum cultures take weeks or months to develop results and microscopy cannot predict viability or resistance patterns. According to a WHO report there were 8.8 million new cases and 1.5 million associated deaths in 2010 with a new TB infection occurring every second. Patients are required to exhale into an airbag which is then passed over metal oxide sensors within the device that detect volatile organic compounds produced by Mycobacterium tuberculosis – the organism that causes TB. Data from the sensors are analysed with the aid of computers and compared against preset values for normal air. The device is capable of rapidly identifying several bacterial species, other than M. tuberculosis. A commercial version of the tool, called DiagNose, will reduce the cost of each TB test to less than US$10, which is far cheaper than conventional diagnostic methods, Marcel Bruins, a Dutch researcher with the eNose company and associated with the project, said. “Our aim is to develop a low-cost, user-friendly TB-screening device that can be used globally. If it turns out, for instance, that TB in Bangladesh differs from TB in Africa, this can be resolved by adjusting the software,” Bruins said. (SciDev)