Letters and replies sions we still wonder how well reported this information is Spurious hepatitis B surface antigen detection in adult to the wider renal community. Such a finding in clinical haemodialysis patients following vaccination practice can cause a major upset to the patient and to the running of a dialysis unit which could be avoided if the Sir, knowledge were more widely available. We thank our col-We read with considerable interest the letter by Riley et al. leagues for this letter and the correction regarding the [1] on the spurious hepatitis B surface antigen detection in previous literature. a haemodialysis patient. We would like to make the following comments. University of Wales College of P.A. Rutherford We agree with the authors that cases of transient post-Medicine vaccination HBsAg positivity needs to be fully acknowledged Wrexham to prevent misdiagnosis, anxiety and confusion. However, Clwyd we disagree with Riley et al. [1] on several points: transient UK detection of hepatitis B vaccine following immunization has been previously described in dialysis patients [2] and was the finding that we observed in 12 adult haemodialysis patients. Note by the Editor-in-Chief Therefore, hepatitis B surface antigenaemia in adult haemodialysis patients is a frequent problem that we identified in The Editor-in-Chief is embarrassed that both Dr Esparza about 30% of the patients who have been vaccinated against and Dr Rutherford fail to carefully read NDT, since a similar hepatitis B viral infection (Engerix B). The final comment observation has been published by Brodersen et al. concerns the duration of antigenaemia. Although it was more Brodersen HP, Beckers B, Kö hler H, Dahlmanns C, frequent after 2-4 days of vaccination, it has been described Kruska L, Larbig D. 'The test for hepatitis B surface antigen after 20 days [2] and in our experience the maximal time of is transiently positive after vaccination with recombinant clearance was 11 days. Thus, to prevent misdiagnosis, dialysis vaccine' Nephrol Dial Transplant 1997; 12: 2756-2757 patients must not be screened for hepatitis B surface antigen for at least 12-21 days after vaccination. Department of Nephrology N. Esparza Renal haemodynamic responses to a chicken or beef