A promising new diagnostic test for detecting drug-resistant tuberculosis (DR-TB) quickly and reliably is finally available, said a new report by Médecins Sans Frontières (MSF).
The possibility that the number of DR-TB cases might treble in South Africa, which has a high TB-burden, highlights the use of this new tool in relation to problems like the pricing and supply of DR-TB medication.
The "GeneXpert" machine - about the size of a milk crate - provides a fully automated nucleic acid amplification test (NAAT) that is effective in the early diagnosis of TB, multidrug-resistant TB (MDR-TB), and TB patients co-infected with HIV, which is more difficult to diagnose.
"I'm so proud to finally have this test," said Xoliswa Harmans, a former patient with extensively drug-resistant TB (XDR-TB) and HIV, whose diagnosis in 2008 took six weeks. "It was very difficult [waiting for my results]. I was very sick. I couldn't eat and was losing weight," said Harmans, who now works as a TB counsellor.
Unlike the previous "gold standard" test, which used a culture technique that could take six to eight weeks, this test - endorsed by the World health Organization (WHO) in December 2010 - provides results in about two hours and has a sensitivity rate of 90 percent.
Another advantage of the new test is its simplicity - it can be used by people who are not necessarily health workers because sputum sample "cartridges" are simply inserted into the machine for diagnosis.
The Ubuntu Clinic in Khayelitsha, about 32km from Cape Town, is so far the only South African clinic to use the test. The township has one of the highest national and global rates for HIV and TB. In 2009, antenatal HIV prevalence was 30 percent, and the case notification rate for TB was at least 1,500 per 100,000 people annually - one of the highest levels of TB infection in the world.
"Because of the rise of HIV, TB has become more prevalent," said Dr Jennifer Hughes, DR-TB co-coordinator for MSF in Khayelitsha. "People with HIV are more susceptible to dying from TB, so if we can diagnose sooner we can get them on treatment sooner."
Patients diagnosed with DR-TB are immediately eligible for ARV treatment, whereas "normal" TB patients are eligible only if their CD4 count (which measures immune system strength) falls below 350.
An integrated, decentralized approach
Cikizwa Jonas, 56, started treatment at the Lizo Nobanda Clinic seven weeks ago. "I take 20 pills a day... After taking all the medication I get nausea and want to vomit."
The City of Cape Town, MSF, and the Western Cape provincial government started this "decentralized" pilot project in 2007 in response to the spread of drug-resistant TB. The Lizo Nobanda clinic is one of 10 in Khayelitsha that form the hub of an integrated yet decentralized community-based approach to TB-care and offers in-patient care for newly diagnosed DR-TB patients.
New patients often suffer the most severe side effects, and the clinic provides a comfortable, safe environment for patients to acclimatize to the treatment without being forced into a lengthy and often isolating hospital stay.
|Treating a drug-resistant TB patient for 24 months can cost up to US$9,000 - 470 times more than the $19 per patient it costs to cure standard TB|
Previously, the long wait for diagnosis and poor tracking of those patients weeks later, followed by an automatic six-month stay in hospital, meant that thousands of DR-TB patients remained undiagnosed, or were diagnosed but had no access to treatment while they continued spreading the disease to others.
The patient-centred approach uses local clinics and includes methods like infection control teams, who visit patients' homes to make alterations that reduce transmission.
"We can provide care at the community and primary care health level, increase case detection and increase the number of patients on DR-TB treatment, which reduces transmission in the community," said Hughes.
"The biggest challenge [to the decentralized method] has been contesting the notion that DR-TB patients needed to be in hospital," Dr Carol Cragg, a medical officer overseeing HIV in Western Cape told a press conference at which MSF reported the first results of the programme.
Among the key successes are improved case detection (up from 118 in
2006 to 231 in 2009) and initiation of treatment (over 80 percent of patients diagnosed in 2009 and 2010 started treatment). The median time from detection to treatment initiation fell from 71 days in 2007 to 33 days in 2010.
Despite the improvements brought by the decentralized approach, and the rapid diagnosis available with the new test, providing treatment is still one of the chief problems.
DR-TB treatment requires standard antibiotics, many of which have severe side effects ranging from constant nausea to deafness, and must be taken as complex daily regimen of numerous pills for up to two years.
Shortages and high prices hound the DR-TB drugs, and the increased case load from using the new test will almost certainly exacerbate these problems. Studies indicate that a full roll-out of the new test could result in a three-fold increase in new DR-TB cases, and a doubling of the number of HIV-associated TB cases.
"If we find the [expected] numbers we'll have to treat them, and that will be very difficult," said Dr Gilles van Cutsem, medical coordinator at MSF in South Africa. Treating one DR-TB patient for 24 months can cost up to US$9,000, which is 470 times more than the $19 per patient it costs to cure standard, drug-sensitive TB.
"Patients have been stuck in a vicious circle - not enough people are diagnosed, and drug supply problems, along with high prices, stand in the way of putting more people on treatment," said Dr Tido von Schoen-Angerer, Executive Director of MSF’s Campaign for Access to Essential Medicines.
"The low demand for DR-TB drugs has made the market unattractive for producers, which is reinforcing supply and price problems," he noted.
TB is a curable disease that kills nearly 1.3 million people each year worldwide, and is the main cause of death in people living with HIV/AIDS in Africa. Of the 9.4 million new tuberculosis cases reported globally each year, 440,000 are multidrug resistant.