Banning serological test kits to fight drug-resistant tuberculosis
CAMBODIA, 12 August 2012 - The recent decision by the Royal Government of Cambodia’s Ministry of Health to ban the manufacture, sale, distribution and use of serological (blood) test kits for diagnosing active tuberculosis (TB) is significant in preventing acquired drug resistance to the disease.
Cambodia is the second country in the Asia-Pacific, after India, to impose the ban following a negative policy statement on serological test kits for TB issued by the World Health Organization last July. The WHO found that commercial serological tests for TB provide inconsistent and imprecise findings that result in highly variable values for sensitivity and specificity. This can seriously jeopardize patient safety.
“Cambodians can be misdiagnosed by serological tests as suffering from TB giving rise to what is known as false positive cases,” said Dr. Mao Tan Eang, Director of the National Centre for Tuberculosis and Leprosy Control.
“The direct fallout of unnecessary medication is the increased chances of people developing acquired drug resistance, thus further complicating and compromising TB care,” he added. “This ban is an important step in preventing drug resistant TB.”
Testing for active TB disease through antibodies or antigens found in the blood is extremely difficult. Patients can have different antibody responses suggesting that they have active TB even when they do not. Antibodies may also develop against other organisms, which again could wrongly indicate they have active TB. In addition, different organisms share the same antigens, making test results unreliable. These factors can result in TB disease not being identified or wrongly diagnosed.
“This is a welcome move to check irrational practices on TB diagnosis in the private sector and it is laudable that the Ministry of Health will now be strict to check this practice among private doctors who prescribe and private labs who conduct these tests,” said Dr. Pieter Van Maaren, the WHO Representative in Cambodia.
Despite great progress during the last decade, tuberculosis is still a serious public health challenge for Cambodia because it has the second highest prevalence rate of TB among the 22 high TB burden countries in the world, after South Africa.
In TB endemic countries, there has been a surge in the demand for serological tests because of its ease and rapidity. Because of this, these tests have always been the first choice for small time private laboratories wanting to mint easy money from the poor.
“Unfortunately, unethical medical practices in the private sector provided major boost to these kits in recent years, without bothering much on quality of tests and implications of false-positive and false- negative results,” said Dr. Pieter Van Maaren.
Pivotal to Cambodia’s fight against TB is the strong commitment of the Royal Government of Cambodia in ensuring that free-of-charge tuberculosis services are available at all government health facilities in the country. This enables access to TB care for poor and vulnerable populations without any cost.
Over the last decade, Cambodia has reported high treatment success rates of well over 90 percent every year. Such high treatment success rates were possible only because of the implementation of the DOTS strategy, which remains at the heart of the National TB Program. The DOTS strategy involves using microscopy to diagnose patients and treating them with a course of anti-TB drugs, with a trained health worker or a community DOT watcher directly observing every dose that the patient takes.
The TB prevalence survey in 2011 has corroborated the immense success of the National TB Program. The preliminary findings of this survey show that point prevalence rate of bacteriological positive TB has declined by 45.6% in the past nine years, since the last prevalence survey in 2002.
Ability to diagnose true TB cases is very critical. Serological tests result in wrong diagnosis. Hence, the ban on serological tests is a major step forward for the National TB Program.
For further information please contact:
Dr Mao Tan Eang
National Centre for Tuberculosis and Leprosy Control (CNET)
Dr Pieter JM Van Maaren
World Health Organization
Dr. Rajendra Yadav
World Health Organization