Summary. A high prevalence of TT virus (TTV), a novel virus recently identi®ed in the serum of a patient with posttransfusion hepatitis of unknown aetiology, has been reported in blood donors worldwide. We investigated the presence of TTV DNA in several lots of blood products and in the corresponding plasma pools. In the process, we determined, from three sets of primers, the one which was most ef®cient in detecting the viral nucleic acid. This set ampli®es the region closest to the 3 H -end of the TTV genome which was proved, by sequence analysis, to be more conserved than the other two regions. Whereas all 10 intravenous immunoglobulin and 21 albumin batches were TTV negative, 4/5 factor VIII concentrates and 4/10 intramuscular immunoglobulin batches were TTV positive. A high prevalence of TTV DNA (70%) was found in the plasma pools that were collected from four different countries. These results con®rm the worldwide distribution of this virus and show that TTV is removed with a varying ef®ciency during the manufacture of blood products.

We recently reported the results of an External Quality Assessment Study (EQA) on HCV RNA plasma pool testing addressed to manufacturers of blood products [1]. The study, carried out in two independent stages during the year 2000, demonstrated an excellent performance of participating laboratories. In fact, using validated nucleic acid amplification technology (NAT), manufacturers of blood products proved to fully comply with the relevant European guideline [2] by showing consistency with their stated detection limit.In order to continue providing laboratories involved in plasma pool testing for HCV RNA by NAT with an external quality measure of their proficiency, we organized a new EQA study for the year 2001. All laboratories, which took part in the previous study, participated in this EQA. In addition, two more manufacturers, one from Argentina and one from Switzerland, and three blood transfusion centres, one from Germany and two from Italy, were accepted as participants. This time the aim of the study was to confirm that participants comply with the European Pharmacopoeia requirement regarding the 100-IU/ml detection level and to verify the absence of cross contamination [3]. Consequently, the panel consisted of the following 20 coded samples: eight negative replicates, 10 replicates containing 100 IU/ml and two replicates containing 17 000 IU/ml. Two Italian reference preparations calibrated against the first WHO HCV RNA International Standard [4], ISS 0498 and ISS 0198, containing 1700 and 17 000 IU/ml, respectively, were used to prepare the positive samples. The former, recently characterized in an international collaborative study [5], was diluted to obtain the 100-IU/ml samples while the latter was used undiluted to prepare the high-titre samples. Before shipping it, the panel was tested in our laboratory by two operators in order to confirm the HCV positivity/negativity of the samples. Participants, who were assigned a random code, were asked to test the panel by their routine procedure. Seven out of the 15 participating laboratories used an in-house method while the rest used a commercial kit. As the samples were scheduled for shipment after 11 September 2001, serious problems with flight connections occurred in the aftermath of the terrorists' attack in the USA. As a consequence, two laboratories received the panel thawed and only in one case was it possible to send a new panel. The deadline for sending the results was postponed from the end of November to mid-December 2001.All 15 participants sent their results including the laboratory that received the panel thawed but decided to test it anyway. As in this case degradation of HCV RNA during the long uncontrolled storage period could not be excluded, we did not evaluate the results of this laboratory. Still, we informed the laboratory of its results as these could be of some use for the participant. With respect to the other laboratories, all samples with a nominal concentration of 100 IU/ml and 17 000 IU/ml tested positive in 100% of the assays. De...

This external quality assessment study showed that manufacturers of blood products have reached a high level of proficiency that fully complies with the European Pharmacopoeia requirements. This finding is reassuring in the context of the safety of blood products.

The HCV EQA/5 showed an improved proficiency of laboratories as compared with the HCV EQA/4. In fact, HCV genotypes 1, 2, 3 and 5 were correctly identified in 100% of the assays and genotypes 4 and 6 in 97.8% of the assays. While most of the participants in the HIV EQA/1 showed a good level of proficiency, an excellent performance was shown by all participants in the HBV EQA/1.

Since the introduction of mandatory HCV RNA testing of plasma pools for fractionation by nucleic acid amplification technology, we have organised External Quality Assessment studies (EQAs) addressed to blood products manufacturers and blood centres. Here we report the results of a new EQA, the first one to include all six major HCV genotypes. The results, reported by laboratories worldwide, showed that genotypes 1, 2 and 3 were correctly identified in 100% of the tests, genotype 4 in 96.7% and genotypes 5 and 6 in 98.3% of the assays. As detection of all HCV genotypes is critical for laboratories involved in testing plasma for HCV, all six genotypes should continue to be included in the next EQA studies.