Maria Wirz

Immunity to diphtheria in the 3–19 year age group in Italy

Diphtheria antibody level in serum samples obtained from 270 subjects aged 4-70 was measured by in vitro seroneutralization test on Vero cells. Of the studied population, 27.8% had an antibody titre below the protective level (< 0.01 IU/ml). The prevalence of susceptible subjects showed a significant age-related increase (p < 0.01), with the highest value (53.8%) in the 31-40 age group. Mean antibody titre was maximum in individuals aged 13-14, then decreased reaching the minimum level in the 41-50 age group. These data suggest that in individuals aged 30-50, diphtheria immunity is not satisfactory, both for prevalence of immune subjects and for antibody levels. Therefore, a revaccination of adults with reduced doses of diphtheria toxoid may be advisable.

Prevalence of TT virus in plasma pools and blood products

A high prevalence of TT virus (TTV), a novel virus recently identified in the serum of a patient with post‐transfusion 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 efficient in detecting the viral nucleic acid. This set amplifies the region closest to the 3′‐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 confirm the worldwide distribution of this virus and show that TTV is removed with a varying efficiency during the manufacture of blood products.

Quantification of hepatitis C virus (HCV) RNA in a multicenter study: implications for management of HCV genotype 1-infected patients.

ABSTRACT Assessment of the viral load in hepatitis C virus (HCV) genotype 1-infected patients is critical before, during, and after antiviral therapy. In patients achieving a rapid virological response at week 4 of treatment, the viral load at the baseline is considered a predictive criterion of a sustained virological response 24 weeks after the discontinuation of treatment. A ≥2-log10 drop in the viral load at week 12 of treatment (early virological response) triggers the continuation of therapy. We organized a multicenter study (MS) for diagnostic laboratories involved in the quantification of HCV RNA. Commercial assays, including two based on real-time reverse transcription-PCR (TaqMan system), and in-house methods, were used by the 61 participants. The overall reproducibility of the commercial quantitative nucleic acid amplification techniques (qNAT) was acceptable. As the intermethod variability among commercial qNAT for HCV RNA was still present, the manufacturers of these test kits should join efforts to harmonize the means of quantification of HCV RNA. This study also shows that caution should be exercised when the baseline viral load is evaluated and when the 2-log10 reduction after 12 weeks of therapy is interpreted. Finally, this MS confirms the higher sensitivity of the commercial qNAT based on the TaqMan system, making them the elective assays for the monitoring of therapy.

External quality assessment for the detection of blood-borne viruses in plasma by nucleic acid amplification technology: the first human immunodeficiency virus and hepatitis B virus studies (HIV EQA/1 and HBV EQA/1) and the fifth hepatitis C virus study (HCV EQA/5)

Background and Objectives  This External Quality Assessment (EQA) study was aimed at assessing the proficiency of blood centres and blood product manufacturers in detecting, by nucleic acid amplification technology (NAT), the possible contamination of plasma with hepatitis C virus (HCV), human immunodeficiency virus (HIV) and hepatitis B virus (HBV).

External quality assessment for the detection of HCV RNA, HIV RNA and HBV DNA in plasma by nucleic acid amplification technology : a novel approach

Background and Objectives  In this EQA study a novel approach was used to assess the performance of blood centres and blood product manufacturers in detecting the possible contamination of plasma with HCV, HIV and HBV by NAT.

Hepatitis C virus testing of plasma pools by nucleic acid amplification technology: external quality assessment

Since 1 July 1999, in accordance with European regulations, only batches of blood products obtained from plasma pools tested and found to be non‐reactive for hepatitis C virus (HCV) RNA are being released. As monitoring the performance of manufacturers involved in plasma pool testing is important to ensure reliable amplification techniques, the Istituto Superiore di Sanità, as the Italian regulatory authority, organized an external quality assessment study.

High proficiency in detecting the six major hepatitis C virus genotypes of laboratories involved in testing plasma by nucleic acid amplification technology

Summary 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.

Tetanus immunity among Italians born after the introduction of mandatory vaccination of children

In Italy systematic mandatory tetanus immunization of children started in 1968. In a national sample of 241 young males born after 1968 the prevalence of non-immune subjects was 11.2% (5.5% in the North-Centre, 15.9% in the South-Islands; p < 0.02). Comparing these data with the corresponding figure obtained in a previous study of subjects born before 1968 a significant decrease (11.2% versus 32.6%; p < 0.01) is observed. The prevalence of non-immune subjects born after 1968 is significantly (p < 0.01) lower than that observed in subjects born before 1968 by geographical area as well as by area (urban/rural) of residence. These findings indicate that the introduction of compulsory tetanus vaccination for all newborns has favourably affected the immune status of younger Italian men. However, more efforts should still be addressed to decrease regional inequalities in the delivery of health care.

Interlaboratory study to evaluate the performance of laboratories involved in West Nile virus RNA screening of blood and blood components by nucleic acid amplification testing in Italy.

BACKGROUND An Italian interlaboratory study was run in 2010 to assess the performance of Blood Transfusion Services in detecting the genome of West Nile virus (WNV) in plasma. MATERIALS AND METHODS Each laboratory received a panel of samples containing four samples negative for WNV and six positive samples with a nominal viral concentration close to or below the 95% detection limit of two commercially available nucleic acid amplification tests (NAT) for WNV, the PROCLEIX® WNV kit and the Cobas® TaqScreen West Nile Virus kit. RESULTS Ten laboratories took part in the study. All correctly identified the positive samples with a viral concentration above the 95% detection limit. No pre- or post-analytical errors were observed. CONCLUSIONS The interlaboratory study run in 2010 allowed participants to assess the performance of the NAT methods applied in their seasonal routine screening of blood donations.

Overestimation of the Hepatitis C Virus RNA Content of Reference Preparations by the AMPLICOR HCV Monitor Test, Version 2.0

ABSTRACT An evaluation of the AMPLICOR hepatitis C virus (HCV) monitor test, version 2.0 (Roche Diagnostics), was carried out to investigate whether this test overestimates the HCV RNA content of reference preparations. Satisfactory accuracy was observed when the World Health Organization HCV international standard was included in the assay and a modified formula was used to calculate the viral content.