From the Editor

EDITOR,-In a thorough investigation, Haga et al were unable to demonstrate the presence of measles virus RNA in intestinal specimens from patients with inflammatory bowel disease (Gut 1996; 38: 211-5). Although they developed an exquisitely sensitive technique, there remains a fundamental flaw in their methodology. They described intestinal tissue postoperative resection times ranging from 20 to 90 minutes. Such prolonged ischaemic times would have reduced the sensitivity of their assay considerably, as substantial RNA degradation would have occurred. MacPherson et al reported a significantly lower yield of RNA in surgical intestinal specimens with ischaemic times of45 minutes to 1 hour 45 minutes compared with biopsy specimens frozen within 15 seconds.' Further degradation can also occur during prolonged storage at -70°C. The assay may be sufficiently sensitive to detect one viral genome, but low copy number RNA species are likely to have been lost on the way. This could be tested by attempting to amplify an intestinal RNA species present in much lower copy numbers than 1-actin from their extracted intestinal RNA samples. The authors must apply their technique to freshly resected intestinal tissue before they can conclude that nested RT-PCR fails to detect measles, mumps or rubella viral genomes. M S H SMITH Department of Gastroenterology, North Staffordshire Hospital, Newcastle Road, Stoke on Trent, Staffordshire ST4 6QG