Nucleic acid testing (NAT) for hepatitis C virus (HCV) and human immunodeficiency virus (HIV) has been implemented in several European countries and in the United States, while hepatitis B virus (HBV) NAT is still being questioned by opinions both in favor and against such an option, depending on the HBV endemicity, health care resources, and expected benefits.This survey was aimed to assess the NAT impact in improving the safety of blood supply in Italy, 6 years after implementation. The study involved 93 Italian transfusion centers and was carried out in 2001 through 2006. A total of 10,776,288 units were tested for the presence of HCV RNA, 7,932,430 for HIV RNA, and 3,405,497 for HBV DNA, respectively.Twenty-seven donations or 2.5 per million tested were HCV RNA-positive/anti-HCV-negative; 14 or 1.8 per million units tested were HIV RNA-positive/anti-HIV-negative; and 197 or 57.8 per million donations tested were HBV DNA-positive/hepatitis B surface antigen-negative. Of the latter, 8 (2.3/10(6)) were collected from donors in the window phase of infection and 189 (55.5/10(6)) from donors with occult HBV. Sixty-eight percent of the latter donors had hepatitis B surface antibody, 74.5 percent of whom with concentrations considered protective (>or=10 mIU/mL).NAT implementation has improved blood safety by reducing the risk of entering 2.5 HCV and 1.8 HIV infectious units per million donations into the blood supply. The yield of NAT in detecting infectious blood before transfusion was higher for HBV than for HCV or HIV. However, the benefit of HBV NAT in terms of avoided HBV-related morbidity and mortality in blood recipients needs to be further evaluated.
The screening strategies for the detection of blood donors potentially able to transmit an infection to the recipient of their blood or blood products have always included clinical, behavioural and laboratory criteria in an attempt to construct a multi-barrier system that most effectively guarantees transfusion safety1. These criteria are necessarily modified over time as further knowledge is acquired and new laboratory tests become available.
Hepatitis B virus (HBV) causes the blood-borne viral infection for which serological markers for screening have been available for the longest time. Indeed, the introduction of a test to detect the hepatitis B surface antigen (HBsAg) at the beginning of the 1970s certainly contributed to a drastic reduction in the number of HBV transfusion-transmitted infections. However, despite continuous improvements in the sensitivity of this test, transfusion-related transmission of hepatitis B has not been completely eliminated and in some countries an additional serological investigation (the search for antibodies against HBV core antigen, anti-HBc) was introduced. Testing for these antibodies was initially used as a surrogate marker for the detection of non-A, non-B hepatitis in the mid-1980s, but after the availability of a specific test for hepatitis C virus (HCV), it returned to being of specific relevance in the screening for HBV infection.
More recently, a test to detect HBV DNA was introduced for the screening of blood donors. Crucially, this test can detect an acute HBV infection earlier than HBsAg and anti-HBc tests, thus reducing the so called window period during which an infected donors may harbour large amounts of infectious viral particles in the absence of serological markers and/or signs and symptoms of an ongoing infection2. Furthermore, DNA testing allows the identification of a number of donors -including periodic donors-characterised by the absence of HBsAg in the presence of HBV DNA with or without anti-HBs, anti-HBc and/or anti-HBe antibodies. These latter serological profiles are defined as occult HBV infection (OBI) in agreement with the Consensus Conference held in Taormina in 20083. In these cases, the amount of HBV DNA -when detectable- is usually very low (<100–200 IU/mL). On the basis of the serological profile, OBI can be distinguished into seropositive (anti-HBc and/or anti-HBs positive) or seronegative (anti-HBc and anti-HBs negative) types3.
The tests that, at present, are mandatory in Italy for the prevention of transfusion-related transmission of HBV include HBsAg (using several commercially available last-generation immunoassays kits) and HBV DNA detection (50% of blood units are tested in pools of 6 samples by Roche Cobas Taqscreen MPX on the Cobas s 201 platform [Roche Instruments Center, Rotkreuz, Switzerland] and 50% in single tests by Novartis Ultrio [Emerville, CA] with comparable analytical and clinical sensitivity4,5). In addition, other serological tests are performed, with a heterogeneous distribution across the country, in part as an additional criterion for the validation of blood components (i.e. anti-HBc) and in part as an evaluation of the immunological status of the donor (i.e. anti-HBs).
A national survey organised by the Italian Society of Transfusion Medicine and Immunohaematology (SIMTI) in 20096 found that 78 (43%) of 181 Transfusion Services (TS) that replied to a specific questionnaire routinely performed anti-HBc and that 53 of these 78 (68%) TS were located in Northern Italy Regions. In most of the TS (81%) participating in the study, this test was carried out in first-time donors only, while in the remaining (19%) it was carried out in all donors. Fifty percent of the TS that performed this test used a positive result for anti-HBc as a criterion to exclude antibody-positive donors from donating while the remaining TS did not.
Thus, there are profound differences in the behaviour of TS, resulting from the persistence of criteria based on serological parameters and criteria derived from the introduction of the new molecular biology tests. In the light of this, SIMTI set up a Working Group charged with the task of defining the screening tests for HBV capable of guaranteeing the highest levels of safety compatible with the possibility of ensuring timely and appropriate transfusion therapy in the specific Italian epidemiological context, with the currently available technology.
The use of NAT technology to screen blood donations in Italy became mandatory on 28 June 2002, but had been available experimentally since 2001. During the transition period, an EIA test to detect hepatitis C core antigen (HCVcoreAg) had also been permitted. Considering the large number of blood transfusion centres in Italy, an initial reorganisation of the biological validation of blood units was necessary, with a partial centralisation of NAT testing. The Gruppo Italiano per lo Studio delle Malattie Trasmissibili con la Trasfusione (Italian Group for the Study of Transfusion-Transmissible Diseases) conducted a national survey evaluating NAT testing, based on an annual collection of data through a questionnaire sent to all centres. In the first three years of the investigation, 219 blood transfusion centres returned the questionnaires. In the period between January 2001 and December 2003, 3 894 894 blood donations were investigated for HCV RNA and 2 186 468 for HIV RNA. Of these, 12 were found to be HCV RNA positive and four HIV RNA positive, with an observed NAT versus antibody-based assay yield of 3.1/106 donations for HCV and 1.8/106 donations for HIV, respectively. Five of the 12 HCV RNA positive and anti-HCV negative donors had abnormal ALT values and their donations would have been discarded even in absence of NAT testing. Thus the final NAT yield for HCV is 1.79/106. The residual risk for HCV or HIV transmission by blood transfusion after NAT implementation is currently estimated to be extremely low in Italy.
ABSTRACT We evaluated the COBAS Ampliscreen hepatitis B virus (HBV) test using standards, seroconversion panels, consecutive donations, and samples from patients with abnormal alanine aminotransferase and chronic hepatitis C. Specificity was 100% and sensitivity was 20 IU/ml. In seroconversion panels, HBV DNA was detected up to 4 to 18 days before HBsAg, suggesting that this assay is useful in shortening the infectious window phase.
Em Italia, o uso do teste de acidos nucleicos (NAT) nas doacoes de sangue e obrigatario desde o 28 de Junho de 2002, embora fora utilizada esta tecnica desde 2001 de modo experimental. Durante o periode de transicao tambem estava permitido o uso de testes enzimaticos (EIA) para a deteccao do antigeno do core do virus da hepatite C (Ag HBc). Considerando o grande numero de centros de transfusao de sangue em Italia, foi necessario reorganizar a validacao biologica das doacoes de sangue com uma centralizacao parcial do teste pelo NAT. O “Gruppo Italiano per lo Studio delle Malattie Trasmissibili con la Trasfusione” (Grupo Italiano de Estudo de Doencas Transmissiveis por Transfusao) realizou um estudo nacional para evaluar o NAT baseado na recolha annual de dados por meio de um questionario enviado a todos os centros. Durante os tres primeiros anos, 219 centros de transfusao responderam ao inquerito.
Entre Janeiro de 2001 e Dezembro de 2003, foram testadas para o virus da hepatite C (VHC) 3.894.894 doacoes de sangue e 2.186.468 para o VIH. Doze testes eram positivos para o VHC, o que representa uma melhoria para o NAT comparado com os testes de anticorpos de 3,1 por milhao de doacoes para o VHC e de 1,8 por milhao de doacoes para o VIH. Cinco dos 12 dadores VHC positivos e anti-VHC negativos tinham valores de TLA anormais; estas doacoes teriam sido recusadas mesmo sem NAT. Assim, o resultado final do NAT para o VHC nao e mais do que 1,79 por milhao de doacoes. Em Italia, desde a implementacao do NAT, o risco residual de transmissao do VHC ou do VIH por transfusao de sangue e extremamente baixo.
BACKGROUND : This study was designed to assess the risk of transmitting HCV and HIV by transfusion of antibody‐screened blood and to estimate the additional reduction in risk that may be achieved through the implementation of direct viral detection assays in Italy. STUDY DESIGN AND METHODS : Clinical and laboratory data of 2,411,800 blood donations collected from repeat volunteer donors from 1996 through 2000 were analyzed. The risk of transmitting HCV or HIV from screened blood donated during the window period was estimated using a mathematical model. RESULTS : The residual risk of donating antibody‐ negative infectious blood was estimated at 1 in 127,000 donations for HCV and 1 in 435,000 for HIV. The use of NAT should further reduce such risk by 83 percent for HCV and 50 percent for HIV. CONCLUSION : The residual risk of HCV or HIV transmission through screened blood is currently very small in Italy. The implementation of direct viral detection assays can further improve the safety of blood supply.
En Italia, el uso de la prueba de acidos nucleicos (NAT) en las donaciones sanguineas es obligatorio desde el 28 de Junio de 2002, aunque esta tecnica se utilizaba desde 2001 de modo experimental. Durante el periodo de transicion, tambien estaba permitido el uso de pruebas enzimaticas (EIA) para la deteccion del antigeno del core del virus de la hepatitis C (Ag HBc). Considerando el gran numero de centros de transfusion sanguinea en Italia, fue necesario reorganizar la validacion biologica de las hemodonaciones con una centralizacion parcial del cribado por el NAT. El “Gruppo Italiano per lo Studio delle Malattie Trasmissibili con la Trasfusione” (Grupo Italiano de Estudio de Enfermedades Transmisibles por Transfusion) ha realizado un estudio nacional para evaluar el NAT basado en la recogida anual de datos por medio de un cuestionario enviado a todos los centros. Durante los tres primeros anos, 219 centros de transfusion respondieron a la encuesta.
Entre Enero de 2001 y Diciembre de 2003, fueron testadas para el virus de la hepatitis C (VHC) 3.894.894 donaciones sanguineas y 2.186.468 para el VIH. Doce pruebas dieron positivas para el VHC y cuatro para el VIH, lo que representa un rendimiento para el NAT comparado con las pruebas de anticuerpos de 3,1 por millon de donaciones para el VHC y de 1,8 por millon de donaciones para el VIH. Cinco de los 12 donantes VHC positivos y anti-VHC negativos tenian valores de TLA anormales; estas donaciones hubieran sido rechazadas incluso sin NAT. Asi, la ganancia final del NAT para el VHC no es mas que 1,79 por millon de donaciones. En Italia, desde la implementacion del NAT, el riesgo residual de transmision del VHC o del VIH por transfusion sanguinea es extremadamente escaso.
