DOCTORS in Hong Kong and Scotland are trying to develop a test for a hepatitis C virus found only in the territory and Macau. They fear that the usual test for the virus does not pick up the new strain, a Chinese doctor working in Edinburgh said. Dr Yap Peng-lee told a joint meeting this weekend of Edinburgh's Royal College of Physicians and the Hong Kong colleges of physicians and paediatricians, that the researchers were expanding their studies into China. They will begin with a trip to Shanghai this week. The hepatitis C virus occurs in several mutations, six of which have been identified so far. The rare C-6 strain was discovered about two years ago only in Hong Kong and Macau, although one Vietnamese immigrant to Canada is also thought to have carried it. 'We know very little about this strain,' said Dr Yap before giving his talk at the two-day meeting. 'It's a bit of a mystery, so I'm very keen to try to extend our studies.' Work with Hong Kong Blood Centre and Queen Mary Hospital has shown up only 12 cases among blood donors, but there are two problems. 'We have a hunch that the test [for C-1] may not be so good for detecting the other strains, and hepatitis C seems to be rare among those who donate blood,' said Dr Yap. He said hepatitis C seemed to be 10 or 100 times less common than hepatitis B, which caused cirrhosis of the liver and could lead to liver cancer, but with such limited figures it was difficult to know. There was hardly any data about China, which might be the source of the C-6 strain, or other countries in the region, he said. Different strains responded differently to interferon treatment, with response rates varying from about 25 per cent response for strain C-1, up to 75 per cent for strains C-2 and C-3. And knowledge of the virus' behaviour would be needed eventually to develop a vaccine, Dr Yap said. He will go to Shanghai tomorrow hoping to set up further collaborations with laboratories to study other blood samples. Dr Yap said it was difficult to find good collaborators to distinguish between the various types.