High prevalence in Switzerland of pure red-cell aplasia due to anti-erythropoietin antibodies in chronic dialysis patients:: report of five cases

Background. Pure red-cell aplasia (PRCA) after erythropoietin (Epo) administration due to the appearance of neutralizing anti-Epo antibodies has been reported in over 200 cases between 1998 and 2002. However, large intercountry disparities were observed in the occurrence of this syndrome. Methods. On behalf of the Swiss Society of Nephrology, a survey was conducted in all the dialysis units of Switzerland in order to collect information on the occurrence, diagnostic and evolution data of the cases observed. A questionnaire was send to the nephrologists in charge of each of the 69 dialysis units in January 2003. The clinical and biological data of the suspected cases were analysed and compared with the data provided to health authorities and pharmaceutical companies. Results. A total of five cases were identified as true PRCA with demonstrated positive anti-Epo antibodies. They occurred between November 1998 and February 2002, were all treated by haemodialysis and had received Epo subcutaneously. The median appearance time of refractory anaemia after Epo initiation was 10 months (range: 7-54 months). Two cases had been treated exclusively with epoietin-alpha, one solely with epoietin-beta and the two others with a combination of both. With five cases out of a total of about 2500 dialysis patients and 2300 Epo-treated dialysis patients or an exposure rate to Epo of 9900 dialysis patient-years during a 4.3 year period, this prevalence is among the highest of those reported in European countries. Conclusions. The prevalence of PRCA after Epo administration in dialysis patients appears particularly high in Switzerland. Among the potential explanations, the most plausible are the high percentage of dialysis patients treated with Epo, the almost exclusive subcutaneous administration, the larger market distribution of the epoietin-alpha brand, the eventual disruption of the cold chain and the setting-up of a systematic national survey.