WHO warns against the use of inaccurate blood tests for active tuberculosis

The use of currently available commercial blood (serological) tests to diagnose active tuberculosis often leads to misdiagnosis, mistreatment and potential harm to public health, says the World Health Organization (WHO) in a policy recommendation issued earlier this week. WHO is urging countries to ban the inaccurate and unapproved blood tests and instead rely on accurate microbiological or molecular tests, as recommended by WHO. These tests are available in 17 of the 22 countries with high burden of TB and in India alone it is estimated that 1.5 million of these tests are used, costing patients nearly US$15 million (Gernier 2011).

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 tests results unreliable. These factors can result in TB disease not being identified or wrongly diagnosed.

"In the best interests of patients and caregivers in the private and public health sectors, WHO is calling for an end to the use of these serological tests to diagnose tuberculosis," said Dr Mario Raviglione, Director of WHO Stop TB Department. "A blood test for diagnosing active TB disease is bad practice. Test results are inconsistent, imprecise and put patients' lives in danger."

This policy recommendation applies to blood tests for active TB. Blood tests for inactive TB infection (also known as dormant or latent TB) are currently under review by WHO.

The new recommendation comes after 12 months of rigorous analysis of evidence by WHO and global experts. Ninety-four studies were evaluated - 67 for pulmonary tuberculosis (TB in the lungs) and 27 for extrapulmonary tuberculosis (TB elsewhere in other organs).  Overwhelming evidence showed that the blood tests produced an unacceptable level of wrong results - false-positives or false-negatives - relative to tests endorsed by WHO.

The research revealed "low sensitivity" in commercial blood tests which leads to an unacceptably high number of patients wrongly being given the 'all clear' (i.e. a false-negative when in reality they have active TB). This can result in the transmission of the disease to others or even death from untreated tuberculosis. It also revealed "low specificity", which leads to an unacceptably high number of patients being wrongly diagnosed with TB (i.e. a false-positive when in reality they do not have active TB). Those patients may then undergo unnecessary treatment, while the real cause of their illness remains undiagnosed, which may then also result in premature death.

More than a million of these inaccurate blood tests are carried out annually to diagnose active TB, often at great financial cost to patients.  Many patients pay up to US$30 per test. There are at least 18 of these blood tests available on the market. Most of these tests are manufactured in Europe and North America, even though the blood tests are not approved by any recognized regulatory body.

"Blood tests for TB are often targeted at countries with weak regulatory mechanisms for diagnostics, where questionable marketing incentives can override the welfare of patients," said Dr Karin Weyer, Coordinator of TB Diagnostics and Laboratory Strengthening for the WHO Stop TB Department. "It's a multi-million dollar business centred on selling substandard tests with unreliable results."

This is the first time WHO has issued an explicit "negative" policy recommendation against a practice that is widely used in tuberculosis care. It underscores the Organization's determination to translate strong evidence into clear policy advice to governments.

Tuberculosis kills 1.7 million people every year, and is the major killer of people living with HIV. Improving the early and effective diagnosis of TB to ensure more lives are saved is a priority action for WHO and the international TB community. TB research is currently underway to bring better and more rapid tests that are easy to administer, effective and accurate.

WHO's Commercial Serodiagnostic Tests for Diagnosis of Tuberculosis - Policy Statement and other related documents are available here 


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  1. This proves that more is research is needed in the field of serology for TB diagnosis rather than giving up. Do not loss heart, the inventor of the light bulb himself faced such challenges: 'I haven't failed, I've found 10,000 ways that don't work' said Thomas Alva Edison.

    Therefore 'Many of life's failures are people who did not realize how close they were to success when they gave up' said Thomas Alva Edison.

    "Even if you're on the right track, you'll get run over if you just sit there." - Will Rogers

    Aluta Continua!

    Dr Charles Namisi
    Email: charlespcn@gmail.com

  2. I agree with Dr Namisi that more research is needed in the field of serology of TB. However I would like to add that no company should be allowed to market their serological TB test KIT unless it is approved by WHO.

    In the past decade or so various companies mainly from Europe marketed various serological TB diagnostic kits in the low income countries like Pakistan. Primary Care Physicians and some specialist started using these test without realizing the sensitivity/specificity of this test. Huge amounts of money was wasted and lot of patients were wrongly diagnosed with TB and some genuine cases of TB were missed. I am very happy to see the warning issued by WHO on these test. Ministry of Health should develop mechanism which can stop foreign or local company for marketing their diagnostic kit in various laboratories of the country.

    Prof Javaid Khan
    The Aga Khan University
    Karachi, Pakistan
    Email: javaid.khan@aku.edu

  3. Further to Dr Javaid Khan's post on Stop-TB eForum emphasizing the need to regulate market for import of substandard and/or unproven diagnostics technologies here is a brief status report of the situation of regulation in Pakistan from where both of us hail.

    As of 1st July 2011 Pakistan has no institutional structure responsible for health sector at the federal level. The federal Ministry of Health was dissolved on the 30 June 2011 under a constitutional amendment leading to devolution of powers to the provincial governments. The amendment (the Eighteenth Amendment of the Constitution of Pakistan) was passed by the National Assembly of Pakistan on April 8 2010 and involves devolution of around 22 federal ministries to the four federating units.

    While the idea of moving the power bases nearer to the people is generally welcomed by most provincial governments at the moment are still at an early stage of preparation to assume the new responsibilities. A sense of confusion and uncertainty prevails in the provincial capitals today. This is happening at a time when Pakistan faces dire need to increase the capacity of the health system to tackle the myriad health problems in the country.

    Drug Act of 1976 the law regulating pharmaceutical sector in the country and the regulatory structures formed under it for registration manufacturing quality assurance of medicines and adjudication of contraventions etc also do not exist anymore under the 18th Amendment. There is no provincial legislation at the moment to fill the gap. A concern has been raised on the devolution of drug regulation at a time when elsewhere in the world countries are moving towards regionalization models of drug regulation.

    Taking such international trends into account one may argue that there ought to be further strengthening of the capacity at the federal level rather than fragmenting it further.

    A ray of hope is in the eminent formation of a national drug regulatory authority approved by the Federal Cabinet
    in 2002 and since languishing for lack of follow up under the auspices of the Implementation Commission formed under the 18th Amendment.

    While these hugely important policy decisions in the country are underway there is little consolation for the discerning citizens in the knowledge that none of this is based on hard evidence and sound research.

    Kind regards

    [PS: this note has been posted at the EDrug list by this scribe]

    Ayyaz Gul Kiani
    Public Health Pharmacist
    Islamabad, Pakistan
    Email: ayyaz_kiani@hotmail.com