An inter- and intra-laboratory comparison of breath ¹³CO2analysis.

BACKGROUND: ¹³C breath test analysis requires accurate ¹³CO2measurements. AIM: To perform a multicentre study to evaluate the repeatability and reproducibility of breath ¹³CO2analysis. METHODS: Two series of 25 paired randomly coded tubes (each consisting of 23 ¹³CO2-enriched breath samples and two samples of standard reference pure CO2with certified δ ¹³C(PDB)) were sent to participating centres for ¹³CO2measurement. Each series of tubes was analysed 10 days apart. The repeatability and reproducibility of ¹³C measurements was assessed by Mandel's k and h statistics. RESULTS: Twenty-two centres participated in the study: 18 showed good inter- and intra-laboratory variability, whilst four showed abnormally high inter- or intra-laboratory variability. Breath test results were also significantly affected by the accuracy of the ¹³C analytical procedures. CONCLUSIONS: A low accuracy of ¹³C measurements may significantly affect the results of breath tests, leading to inappropriate clinical decisions. Standardization of ¹³C analysis is required to guarantee optimal ¹³C measurements and accurate ¹³C breath test results.

Re-treatment with interferon-beta of patients with chronic hepatitis C virus infection.

OBJECTIVE: To evaluate the efficacy of interferon-beta (IFN-beta) in the re-treatment of patients with chronic hepatitis C who did not respond to IFN-alpha monotherapy. PATIENTS AND METHODS: Thirty patients (24 men and six women; mean age, 41 +/- 13 (SD) years; range, 23-62 years), with chronic hepatitis C that was non-responsive to a standard course of IFN-alpha therapy, were re-treated with recombinant human IFN-beta-1a. All patients received IFN-beta, 12 MIU subcutaneously, three times weekly for 3 months, after which time patients' responses were evaluated. Responders (normal alanine aminotransferase, and negative for serum hepatitis C virus RNA) continued to receive IFN-beta, 12 MIU, for a further 3 months. Non-responders had their dose increased to 18 MIU for the remaining 3 months of treatment. After 6 months of treatment, therapy was stopped and patients were followed-up for a further 6 months. RESULTS: Overall, six (20%) of the 30 patients exhibited a response at the end of treatment. One patient (3.3%) maintained a sustained virological response at the end of post-treatment follow-up. CONCLUSIONS: Treatment with recombinant IFN-beta, at doses of up to 18 MIU for 6 months, is safe and well tolerated. However, the results of the trial do not support the use of IFN-beta monotherapy in patients with chronic hepatitis C that is resistant to IFN-alpha.