An Oxford University spin-off company has raised £7m to finance the worldwide sale of its revolutionary test for diagnosing tuberculosis.

Oxford Immunotec, which launched its blood-test kit last year, is exploiting inventions by Dr Ajit Lalvani, Wellcome senior research fellow at Oxford University.

The kit could replace the 100-year-old skin test for the disease, known as TB.

The new diagnostic test improves the speed and accuracy with which TB can be identified.

It is the only test which indicates that people are carrying latent TB before they develop the active disease and infect others.

The World Health Organisation has pronounced TB a "Global Emergency."

In the last ten years 88 million people contracted the disease, 30 million of whom died.

Tuberculosis is staging a resurgence in the developed world.

In the UK, the number of people diagnosed with TB has risen almost every year for the past 15 years, with about 6,500 new cases diagnosed each year.

Dr Lalvani's T Spot TB test analyses the white blood cells produced by the body to fight TB infection.

In this way, it can judge whether a person is infected and how he or she is responding.

The potential market for the test is worth £400m.

The company says the technology could improve diagnosis of many other infectious diseases.

Venture capitalist company Prelude Ventures invested £2.75m, alongside Quester, the Dow Chemical Company, and Top Technology.

Dr Rob James, of Prelude, said: "Often wrongly assumed a problem of a bygone age, TB is now incredibly common worldwide and is steadily on the rise.

He added: "The business is already producing revenues and is on the path to profitability.

"We are enthusiastic to be involved with a company which holds such exceptional and potentially crucial technology."

Oxford Immunotec chief executive Dr Peter Wrighton-Smith said: "The T Spot TB test revolutionises the way in which we detect this widespread and dangerous disease.

"We have approval in the EU and in many other countries further afield and we have strong prospects for the use of our patented technology for the diagnosis of other infectious diseases.

"We are excited to be working with Prelude, who are achieving profitability and who have a strong track record in supporting the rapid development of companies such as Oxford Immunotec."