A significant and largely untapped global market exists for more effective and affordable tests to diagnose TB in low- and middle-income countries, where most TB cases occur. This is the major finding of a new report, Diagnostics for tuberculosis: Global demand and market potential, which was released by the WHO's special programme for Tropical Disease Research and Training (WHO/TDR) and the Foundation for Innovative New Diagnostics (FIND).

Most people in the world who have TB or live in TB risk areas, do not have good access to rapid and accurate testing, says the report. Improved tests could bolster international TB control efforts and respond to a significant market demand, adds the report, which calls for industry investment in new diagnostic tools targeted to low- and middle-income countries.

One third of the world's population is infected with latent TB and at risk of developing the active disease. HIV is fuelling TB epidemics in many countries and multi-drug resistance is a growing threat. Two million people a year die from TB, many because the infection goes undiagnosed, or is diagnosed too late to be cured.

"The TB and HIV threat continues to grow in many parts of the world, and governments need high quality diagnostics to help manage these epidemics," says Dr. Robert Ridley, director of TDR. "We need simple tests to accurately screen for, and identify, active TB. New tests also are needed to monitor treatment response, to identify bacterial drug resistance, and to detect latent infection in people at greatest risk for progression to active TB."

Of the estimated 9 million people who develop active TB every year, most still do not receive a lab-confirmed diagnosis. Only about 2.2 million TB cases annually are diagnosed and reported with sputum smear microscopy, the most widely available test. Other cases are diagnosed through an often wasteful combination of chest X-rays, bacterial cultures and guesswork.

The global market for TB diagnostics is more than twice that of the market for drugs used to treat the disease. Worldwide, about US $1 billion is spent on TB tests and evaluations, which screen some 100 million people annually; around US $300 million is spent on drugs for treatment.

In low- and middle-income countries where three-quarters of the TB tests and screenings are carried out, around US $326 million annually is spent on TB diagnostics. An even larger potential market exists for more effective and affordable tools. Between 70 and 90 per cent of the potential available market for new TB diagnostics is concentrated in 22 countries with the highest burden of TB.

High-tech molecular and rapid culture diagnostics available in developed countries are too complex and costly for many settings where TB is most prevalent, the report notes. Yet traditional sputum smear, X-ray and culture tests may not accurately identify active TB, particularly in HIV-positive patients. Such diagnostics also may fail to make critical distinctions between latent and active TB, and between drug-sensitive and drug-resistant forms of the disease.

"The technology exists to make better TB tools, and this report leaves no doubt that there is a large global market," said Dr Giorgio Roscigno, CEO of FIND. "There is a huge opportunity for diagnostics developers to expand their investments to meet this very real need. We need to use this market analysis to encourage the development of accurate, affordable and easy-to-use diagnostics for developing countries."

The report represents the first time an international network of researchers and policy experts has examined the full range of tests available on the market for: active disease; latent infection; drug resistance; and treatment response. The report was financed by the Bill and Melinda Gates Foundation, and involved more than 100 public health and industry experts as well as several international agencies.

Despite increased global funding for TB control and the emergence of public-private partnerships to support product development, commercial interest in TB diagnostics has been limited by a dearth of information on the size and character of the TB diagnostics market, especially in the developing world, the report states. The majority of recently developed tests serve sophisticated labs in industrialised countries, where less than 5% of global TB cases are found.

"The world urgently needs new, safe and affordable diagnostics to simplify case detection," said Dr Mario Raviglione, Director of WHO's Stop TB Department. "Despite scientific progress that is rapidly changing other fields, most of the world's TB patients have access only to conventional microscopy, which requires repeated testing, may miss half the cases, and which works especially poorly for HIV co-infected patients".

In middle- and low-income countries alone, over 66 million sputum microscopy examinations, 39 million chest X-rays, and 8.5 million cultures are performed each year on suspected TB patients using technologies developed 50 to 100 years ago. The report found striking regional variations in testing, with Russia, India and South Africa together accounting for 91% of TB cultures performed in TB-endemic countries, and Asia making up 68% of the global chest X-ray market.

Compared to vaccines and medicines, the cost of developing new diagnostics and adapting existing ones is relatively low - about US $1-10 million per technology platform, the report notes. It projects demand for seven hypothetical products that could feasibly be developed within such an investment scale.

A test that detects latent infection and predicts progression to active disease could see the greatest use, with a potential available market of some 204 million patient evaluations a year, the report concludes, stating: "Such a test, if widely implemented and accompanied by successful treatment, could revolutionize TB control."

Jean-Francois de Lavison, President of the European Diagnostics Manufacturers Association, called the report "ground-breaking" and highlighted how it "sets out clearly the problems surrounding the existing tests and explains what kinds of improved diagnostic tools are needed and where they could have their greatest impact."