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Nucleic Acid Testing (nucleic + acid_testing)

Distribution by Scientific Domains

Medical Sciences	83%
Life Sciences	16%

Selected Abstracts

Nucleic Acid Testing (NAT) of Organ Donors: Is the ,Best' Test the Right Test?

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 4 2010
A Consensus Conference Report
Nucleic acid testing (NAT) for HIV, HBV and HCV shortens the time between infection and detection by available testing. A group of experts was selected to develop recommendations for the use of NAT in the HIV/HBV/HCV screening of potential organ donors. The rapid turnaround times needed for donor testing and the risk of death while awaiting transplantation make organ donor screening different from screening blood-or tissue donors. In donors with no identified risk factors, there is insufficient evidence to recommend routine NAT, as the benefits of NAT may not outweigh the disadvantages of NAT especially when false-positive results can lead to loss of donor organs. For donors with identified behavioral risk factors, NAT should be considered to reduce the risk of transmission and increase organ utilization. Informed consent balancing the risks of donor-derived infection against the risk of remaining on the waiting list should be obtained at the time of candidate listing and again at the time of organ offer. In conclusion, there is insufficient evidence to recommend universal prospective screening of organ donors for HIV, HCV and HBV using current NAT platforms. Further study of viral screening modalities may reduce disease transmission risk without excessive donor loss. [source]

Provider Utilization of High-Risk Donor Organs and Nucleic Acid Testing: Results of Two National Surveys

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2009
L. M. Kucirka
Fears of infectious transmission from CDC high-risk donors (HRDs) remain a significant disincentive, and the potential for human immunodeficiency virus/hepatitis C virus (HIV/HCV) nucleic acid testing (NAT) to allay these fears remains unstudied. We hypothesized that NAT, which narrows the window period between infection and detectability compared to the standard ELISA, might lead to increased provider willingness to use HRDs. Between January and April 2008, we performed two national surveys: one of current NAT practice among organ procurement organizations (OPOs); a second of HRD use among transplant surgeons. Surgeons who reported accepting 10% or more offers for a given HRD behavior and organ type were classified as ,high utilizers' of that subgroup. We built hierarchical models to examine associations between OPO NAT performance and provider utilization. Providers who ranked medical risks of HIV or HCV as important disincentives to HRD use had significantly lower odds of being high utilizers (HIV odds ratio 0.22, HCV odds ratio 0.41, p < 0.005). Furthermore, both HIV and HCV NAT performance were associated with significantly higher odds of being high utilizers (HIV odds ratio 1.58, HCV 2.69, p < 0.005). The demonstrated associations between OPO NAT performance and high provider utilization of HRDs should be considered in the ongoing debate about NAT in transplantation. [source]

Viral Nucleic Acid Testing (NAT) and OPO-Level Disposition of High-Risk Donor Organs

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2009
L. M. Kucirka
The use of Public Health Service/Centers for Disease Control and Prevention (PHS/CDC) high-risk donor (HRD) organs remains controversial, especially in light of a recent high-profile case of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) transmission. Nucleic acid testing (NAT), while more expensive and time consuming, reduces infectious risk by shortening the period between infection and detectability. The purpose of this study was to characterize HRDs and disposition of their organs by organ procurement organization (OPO), to measure NAT practices by OPO and to examine associations between NAT practices and use of HRD organs. We analyzed 29 950 deceased donors (2574 HRDs) reported to UNOS since July 1, 2004 and May 8, 2008. We then surveyed all OPO clinical directors about their use of NAT, average time to receive NAT results, locations where NAT is performed and percentage of the time NAT results are available for allocation decisions. In total, 51.7% of OPOs always perform HIV NAT, while 24.1% never do. A similar pattern is seen for HCV NAT performance, while the majority (65.6%) never perform HBV NAT. AIDS prevalence in an OPO service area is not associated with NAT practice. OPOs that perform HIV NAT are less likely to export organs outside of their region. The wide variation of current practice and the possibility that NAT would improve organ utilization support consideration for a national policy. [source]

Nucleic Acid Testing (NAT) of Organ Donors: Is the ,Best' Test the Right Test?

Viral Nucleic Acid Testing (NAT) and OPO-Level Disposition of High-Risk Donor Organs

Comparison of different methods of bacterial detection in blood components

ISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue 1 2009
M. Schmidt
Background, Over the last two decades, the residual risk of acquiring a transfusion-transmitted viral infection has been reduced to less than 1 : 1 000 000 via improvements in different techniques (e.g. donor selection, leuco-depletion, introduction of 3rd or 4th generation enzyme-linked immunosorbent assays and mini-pool nucleic acid testing (MP-NAT). In contrast, the risk for transfusion-associated bacterial infections has remained fairly stable, and is estimated to be in a range between 1 : 2000 and 1 : 3000. Platelets are at an especially higher risk for bacterial contamination, because they are stored at room temperature, which provides good culture conditions for a broad range of bacterial strains. To improve bacterial safety of blood products, different detection systems have been developed that can be divided into culture systems like BacT/ALERT or Pall eBDS, rapid detection systems like NAT systems, immunoassays and systems based on the FACS technique. Culture systems are used for routine bacterial screening of platelets in many countries, whereas rapid detection systems so far are mainly used in experimental spiking studies. Nevertheless, pathogen-reduction systems are currently available for platelet concentrates and plasma, and are under investigation for erythrocytes. Methods, In this review, the functional principles of the different assays are described and discussed with regard to their analytical sensitivity, analytical specificity, diagnostic sensitivity, diagnostic specificity and clinical efficiency. The detection methods were clustered into three groups: (i) detection systems currently used for routine screening of blood products, (ii) experimental detection systems ready to use for routine screening of blood products, and (iii) new experimental detection systems that need to be investigated in additional spiking studies and clinical trials. Results, A recent International Society of Blood Transfusion international forum reported on bacterial detection methods in 12 countries. Eight countries have implemented BacT/ALERT into blood donor screening, whereas in three countries only quality controls were done by culture methods. In one country, shelf-life was reduced to 3 days, so no bacterial screening was implemented. Screening data with culture methods can be used to investigate the prevalence of bacterial contamination in platelets. Differing results between the countries could be explained by different test definitions and different test strategies. Nevertheless, false-negative results causing severe transfusion-related septic reactions have been reported all over the world due to a residual risk of sample errors. Rapid screening systems NAT and FACS assays have improved over the last few years and are now ready to be implemented in routine screening. Non-specific amplification in NAT can be prevented by pre-treatment with Sau3AI, filtration of NAT reagents, or reduction of the number of polymerase chain reaction cycles. FACS systems offer easy fully automated handling and a handling time of only 5 min, which could be an option for re-testing day-5 platelets. New screening approaches like immunoassays, detection of bacterial adenosine triphosphate, or detection of esterase activity need to be investigated in additional studies. Conclusion, Bacterial screening of blood products, especially platelets, can be done with a broad range of technologies. The ideal system should be able to detect one colony-forming unit per blood bag without a delay in the release process. Currently, we are far away from such an ideal screening system. Nevertheless, pathogen-inactivation systems are available, but a system for all blood components will not be expected in the next few years. Therefore, existing culture systems should be complemented by rapid systems like NAT or FACS especially for day-5 platelets. [source]

Influence of epidemiological factors on blood transfusion

ISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue 1 2007
S. Laperche
The prevalence, incidence and risk factors of infectious diseases observed in the general population have been described to directly influence transfusion medicine, especially the blood selection. The objective is to ensure the blood safety. The characterization of modes of transmission influences the donor selection: the risk factors of the main blood-borne infections have permitted to adapt the pre-donation questionnaire in order to exclude at-risk donors. The prevalence of infections also has an impact on the blood screening strategy. For example, anti-HBc antibody (Ab) screening is currently performed only in countries where the HBV prevalence is compatible with a reasonable number of donor exclusions. HTLV Ab screening is implemented in countries in which the rate of donors originating from endemic areas could represent a risk for blood components. Measurement of incidence which contributes to the residual risk has led to the introduction of nucleic acid testing (NAT) for HIV, HCV and in some cases for HBV in viral screening strategy in many countries worldwide. The observed NAT yield differs according to the incidence of the infection and according to the country. Finally, the putative blood transmission of new and emerging pathogens has led to implement specific and non-specific measures in order to enhance blood safety. Conversely, although the blood donor population is selected, the data observed in this population have also contributed to better understand epidemiology and pathogenesis of infection. Moreover, owing to the recent progress in developing modelling approaches for estimating risk, we are able to anticipate a transfusion transmission threat by introducing, when necessary, specific measures intended for reduce this risk. [source]

Prevention of hepatocellular carcinoma complicating chronic hepatitis C

JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 4 2009
Yoshiyuki Ueno
Abstract Chronic hepatitis C virus (HCV) infection accounts for most cases of hepatocellular carcinoma (HCC) in Japan and is the second major cause in many other countries. Development of HCC takes a considerable time after onset of HCV infection, between 20,40 years in most cases, and usually develops after cirrhosis is established. Although only a minority of HCV infections reach this stage, the high prevalence of chronic HCV infection in many countries (1,3%) is such that HCC related to HCV infection poses a significant public health issue 20,50 years after the onset of HCV epidemics. Due to advances in testing, and accessibility of clean, disposable medical apparatus including syringes and needles, and particularly screening of donor blood for anti-HCV and by nucleic acid testing, new cases of HCV infection have decreased in most countries, except for continued transmission by injection drug users (IDU). A key difference between HBV and HCV infection is that HCV can be eradicated by effective antiviral treatment. Sustained eradication of HCV reverses hepatic fibrosis, thereby preventing progression to cirrhosis and risk of HCC. Further, it has been well demonstrated that interferon-based antiviral therapy suppresses development of HCC in high-risk patients, particularly when sustained viral response (SVR) is obtained. In summary, the two key approaches to prevent development of HCV-related HCC are primary prevention of HCV infection (adequate programs to screen donor blood, universal precautions to stop medical transmission of blood-borne viruses, curbing transmission by IDU) and potent antiviral therapy of chronic HCV infection. [source]

Failure to confirm HIV infection in two end-stage HIV/AIDS patients using a popular commercial line immunoassay

JOURNAL OF MEDICAL VIROLOGY, Issue 9 2008
Julian W. Tang
Abstract Immunoassays using either viral lysate (Western blot) or recombinant/synthetic antigen (immunoblot) for anti-HIV capture are still the preferred method to confirm HIV infection. Two cases of HIV-1-infected patients presented with acquired immunodeficiency syndrome (AIDS)-defining illnesses. Laboratory tests were performed using multiple commercial HIV test kits on multiple sera from both patients over several weeks. Both patients were strongly positive on the anti-HIV/p24 antigen combined screening assay. Yet, HIV-1 infection could not be confirmed using a popular commercial immunoassay. Eventually, HIV infection was confirmed using an alternative commercial Western blot assay as well as an HIV quantitative PCR test. In laboratories without nucleic acid testing (NAT) for HIV, indeterminate results may delay confirmation of HIV infection, if commercial line immunoassays alone are available. Some end-stage HIV/AIDS patients may not produce antibodies to specific HIV antigens and may therefore give indeterminant or negative results on some immunoassays, depending on the type of antigen used. This report highlights the utility of having NAT available when diagnosing difficult cases of HIV infection, especially in light of the recent Centers for Disease Control and Prevention move towards more universal, routine, HIV testing. J. Med. Virol. 80:1515,1522, 2008. © 2008 Wiley-Liss, Inc. [source]

Detection of Mollicutes in bioreactor samples by real-time transcription-mediated amplification

LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2010
S. Laborde
Abstract Aim:, Contamination by Mollicutes is a significant challenge for research laboratories and biopharmaceutical industry. It leads to alteration of results or production quality as well as loss of time, materials and revenue. These organisms can czoriginate from mammalian, avian, insect, plant or fish cells. Culture-based methods may require 28 days to detect Mollicutes. Traditional microbiology could advantageously be replaced by nucleic acid testing for earlier detection. Methods and Results:, A membrane filtration-based concentration of the Mollicutes has been coupled to real-time transcription-mediated amplification (real-time TMA) to demonstrate these advantages. The eight species required by European Pharmacopoeia have been tested and were detected with sensitivity below 100 CFU per 20-ml sample. Co-culture experiments, in which Mollicutes are grown with CHO-S (suspension) or HEK 293 (adherent) cells, were also performed to respectively mimic a bioreactor or flask contamination. Despite the fact that Mollicutes can attach to or invade mammalian cells, they were consistently detected over multiple days. Conclusions:, the sample preparation and amplification method used in this study increases sensitivity and reduces time-to-result for detection of Mollicutes. Significance and Impact of the Study:, the described system allows real-time monitoring for microbial contamination of cell-based processes and products for the biopharmaceutical industry. [source]

Provider Utilization of High-Risk Donor Organs and Nucleic Acid Testing: Results of Two National Surveys

Transplantation Microbiology: An Evolving Pillar of Transplant Care

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2009
J. A. Fishman
Standardization of nucleic acid testing is an important component of the management of transplant recipients, for microbiologic diagnosis, to guide therapy of viral infections and post-transplant lymphoproliferative disorders, and to assess the intensity of immunosuppression. See also articles by Preiksaitis et al on pages 258 and 269 in this issue. [source]