Critics of the judgment said there is now a legally enforced monopoly over the supply of hepatitis C blood tests to the NHS. They said the transfusion service will have to pay more for tests based on an American patent and the monopoly will hamper research into lethal liver disorders caused by hepatitis C. The transfusion service uses nearly 3 million hepatitis C tests a year and worldwide about 100 million units of blood are screened for the virus.
Professor Roger Williams, director of the Institute of Liver Studies at King's College London, said the judgement was ''absolutely monstrous''. ''It inhibits other companies doing research. It's very bad news for medicine.''
Mr Justice Aldous granted a permanent injuction against the sale of a hepatitis C test made by Murex Diagnostics Ltd and reaffirmed his earlier ruling that the company has infringed a patent on hepatitis C by the Chiron Corporation of California, which discovered the virus in 1987.
A patent that creates a monopoly stimulates technical progress in a number of ways, the judge said in his judgment. It encourages research, discourages secrecy, offers a reward to an inventor and gives an inducement to investors.
''It is inherent in any patent system that a patentee will acquire a monopoly giving to him a right to restrict competition and enabling him to put up or at least maintain prices. That is contrary to the public interest, but it is the price that has been accepted to be necessary to secure the advantages to which I have referred.''
He added: ''There can be no doubt that the Chiron patent monopoly will in the short term deter some companies from carrying out research and development, but that is inherent in the patent system.''
John Barbara, head of microbiology at the North London Tranfusion Centre, said the judgment ''conforms to the letter of the law but in terms of the spirit of competition, it's a sad result''.
Dr Barbara is one of the inventors of the Murex test but receives no royalties himself. He said creating a monopoly will not bring down the cost of the hepatitis C test, which at pounds 2 each is about four times the price of comparable blood tests for other viral infections.
William Burns, managing director of Ortho Diagnostic Systems, which holds a licence on the Chiron patent, denied that the injunction creates a monopoly. He said there are two other companies supplying hepatitis C tests to the NHS on a licence from Chiron.
He said Ortho Diagnostics could easily supply all of the nation's needs for hepatitis C tests. ''Removing the Murex product from the market is not life-theatening in the least.''
Murex has appealed against the ruling.