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Biomedical subjects

E M Dax

Publications and source records attributed to E M Dax.

At least 19 recordsLinked to original sources
PubMed2003

Quality assessment program for genotypic antiretroviral testing improves detection of drug resistance mutations.

Genotypic antiretroviral testing is now widely used for the management of patients who are undergoing antiretroviral therapy for human immunodeficiency virus infection. The assays are complex, and there is considerable potential for variation between laboratories. Informative and ongoing quality assessment programs (QAPs) which address all aspects of testing are required. The panel distribution of clinical material is a critical component of QAPs. We report on the results and data from a recent panel. Four cryopreserved plasma samples from treated donors were distributed to nine laboratories. Three laboratories performed testing by commercial assays, and six laboratories used in-house assays, with one laboratory reporting results from two in-house assays. There was complete concordance between results for 95.9% of the nucleotide sequence and 94.5% of the amino acid sequence. Despite this overall high level of concordance, the degree of concordance at drug resistance mutation (DRM) sites when DRMs were present was considerably less (38% of DRM sites). Consequently, only 3 of the 10 methods reported 100% of DRMs as present. This elevated discrepancy rate is almost certainly a result of variability in the identification of mixtures of nucleotides (mixtures) at any site within the sequence. In addition, laboratories differed in the number of codons in the reverse transcriptase gene that were sequenced and their ability to amplify all samples. This panel distribution demonstrated a requirement for laboratory participation in ongoing QAPs and the optimization of assays with standards that contain mixtures.

Anti-HIV Agents↗
PubMed2001

Variant Creutzfeldt-Jakob disease in Australian blood donors: estimation of risk and the impact of deferral strategies.

BACKGROUND AND OBJECTIVES: In Australia, a policy of deferring donors who have lived in the UK for longer than 6 months between 1980 and 1996 has been instituted to reduce the theoretical risk of transmitting variant Creutzfeldt-Jakob disease (vCJD) through the blood supply. The objective of this report was to refine estimates of the possible risks and benefits of donor-deferral strategies that are aimed at avoiding transmission of vCJD. MATERIALS AND METHODS: Estimates of the effect of donor deferral on the blood supply in Australia were based on a 1998 survey of blood donors. The number of donations from donors potentially infected with vCJD and excluded by donor deferral was estimated based on published estimates of the size of the vCJD epidemic in the UK and assuming that the risk of vCJD in Australian blood donors was proportional to the time lived in the UK between 1980 and 1996. The possible increased number of blood donations that were infected with human immunodeficiency virus (HIV), hepatitis C virus (HCV) or hepatitis B virus (HBV) and made during a window period (as a result of increased donations from first-time donors) was estimated using published methods. RESULTS: A strategy of deferring donations in Australia from people who have lived in the UK for 6 months or longer, between 1980 and 1996, was estimated to result in exclusion of 5.3% of all blood donations, corresponding to 50 100 donations in 1998. It was estimated that the annual number of blood donations made by donors potentially infected with vCJD is 1.15 (range 0.02--31.1, based on the uncertainty in the UK prevalence estimate). Donor deferral was estimated to remove 0.92 (range 0.02--25.1) of these donations. Replacement of 33%, 50% and 100% of excluded donations by donations from first-time donors, was estimated to result in an increase of 0.0010, 0.0019 and 0.0044, respectively, of HIV-infected donations per year donated during the window period; in an increase of 0.021, 0.038 and 0.089, respectively, of HCV-infected donations per year; and in an increase of 0.18, 0.33 and 0.76, respectively, of HBV-infected donations per year. CONCLUSIONS: The large uncertainties involved in these analyses mean that estimates must be interpreted cautiously, but the data does suggest that donor deferral may exclude more donations from donors potentially infected with vCJD than the corresponding increase, caused by donor replacement, of window-period donations possibly infected with HIV, HCV or HBV.

Australia↗
PubMed2000

Quality of human immunodeficiency virus viral load testing in Australia.

This study determined the proficiencies of laboratories measuring human immunodeficiency virus type 1 (HIV-1) viral loads and the accuracies of two assays used for HIV-1 viral load measurement in Australia and investigated the variability of the new versions of these assays. Quality assessment program panels containing (i) dilutions of HIV-1 subtype B, (ii) replicates of identical samples of HIV-1 subtype B, and (iii) samples of subtype E and B were tested by laboratories. Total variability (within and between laboratories) was tested with quality control samples. The coefficients of variation (CVs) for the Roche AMPLICOR HIV-1 MONITOR version (v) 1.0 and Chiron Quantiplex bDNA 2.0 assays ranged from 53 to 87% and 22 to 31%, respectively. The widespread occurrence of invalid runs with the AMPLICOR HIV-1 MONITOR 1.0 assay was identified. The CVs of the new versions of the assays were 82 to 86% for the AMPLICOR HIV-1 MONITOR v 1.5 assay and 16 to 23% for the Quantiplex bDNA 3.0 assay. For virus dilution samples, all but 5 of 19 laboratories obtained results within 2 standard deviations of the mean. The Quantiplex bDNA 2.0 assay reported values lower than those reported by the AMPLICOR HIV-1 MONITOR version 1.0 assay for samples containing HIV-1 subtype B, whereas the reverse was true for subtype E. Identification and resolution of the problem of invalid runs markedly improved the quality of HIV-1 viral load testing. The variability observed between laboratories and between assays, even the most recent versions, dictates that monitoring of viral load in an individual should always be by the same laboratory and by the same assay. Results for an individual which differ by less than 0.5 log(10) HIV-1 RNA copy number/ml should not be considered clinically significant.

Australia↗
PubMed1999

Standardisation of subjectively scored HIV immunoassays: developing a quality assurance program to assist in reproducible interpretation of results using an anti-HIV particle agglutination assay as a model.

Immunoassays such as particle agglutination assays, rapid tests and western or line blots are scored or read subjectively. These readings display intra- and inter-reader variability, as well as intra- and inter-laboratory variability. In the present study the consistency of scoring was assessed between readers both within and between two groups of scientists using the Serodia anti-HIV particle agglutination assay as an example of an assay scored subjectively. An anti-HIV positive sample in eight serial dilutions made to yield a full range of results expected for the assay was presented 12 times (96 test wells). Each dilution was placed randomly in a plate and tested with the Serodia anti-HIV particle agglutination assay then photographed. Participants in the two groups each scored the photographed plate independently and twice, 2 h apart. Each well was assigned a status (the consensus result of the four most experienced Australian readers) and each participant's results were compared with this status. The average percentage of wells assessed as 'correct' for the Group A participants was 86% (range 56-98%) and for the Group B participants was 67% 'correct' (range 46-88%). In general, strongly positive and negative wells were scored 'correctly'. The highest variations between scores were seen in the borderline positive dilutions +/- region. A quality assessment program based on the method used to obtain these results will be instituted in order to improve the consistency of scoring assays read subjectively.

AIDS Serodiagnosis↗
PubMed1997

Assays for HIV with improved sensitivity and specificity.

Increased knowledge of the human immunodeficiency virus (HIV) and the infection it causes in humans has resulted in an enormous expansion in the understanding of viral parameters and host changes. HIV is a virus which mutates readily and rapidly, presenting many challenges to assay developers, and monitors of therapy and drug-resistance. Prolific viral replication at all the stages of the disease means that an accurate assessment of viral burden, viral load and changes to immune system markers is essential for effective clinical management and treatment. In the present review we have summarised current opinion on the kinetics of HIV infection and the pathogenesis of the disease it causes, and have provided a background to the evolution of HIV assays. Sensitivities and specificities of assays used for anti-HIV and HIV detection have improved, and new assays have been developed employing novel molecular techniques, which are being applied to meet continually evolving demands for more sensitive measurement of an increasing number of parameters. The future of HIV testing is also considered in the light of new knowledge concerning virus dynamics in vivo, the likelihood of the emergence of new subtypes and the changing approach to therapy. Assays will be, on the whole, used to quantify virus and to measure the host reactions to infection, often in the presence of antivirals. Thus, extreme sensitivity and specificity will be required.

Journal Article↗
PubMed1995

Multisite evaluation of four anti-HIV-1/HIV-2 enzyme immunoassays. Australian HIV Test Evaluation Group.

The performance of four enzyme immunoassays, manufactured by Abbott, Diagnostics Pasteur, Genetic Systems, and Organon Teknika, for the combined detection of anti-human immunodeficiency virus type 1 (HIV-1) and anti-HIV-2, was examined in a multisite evaluation. The collaborative efforts of 7 Australian Red Cross Blood Transfusion and 12 Australian Public Health Laboratories minimized potential biases in data by providing large numbers of anti-HIV-1-negative and -positive samples. Sensitivity was estimated using samples that were positive for anti-HIV-1 from individuals known to be infected and seroconversion samples. Sensitivity estimates in the four assays were 99.71, 99.94, 99.49, and 99.68%, respectively. Specificity was measured using fresh, sequential blood donations and samples with previous false-positive reactions in other assays. Specificity estimates from blood donations were 99.92, 99.46, 99.67, and 99.85%, respectively. The data were analyzed further using the delta statistic, which distinguishes the performance of assays of similar sensitivity and specificity by providing a measure of how well results in a population of positive or negative samples are removed from the assay's cutoff value.

Australia↗
PubMed1993

HTLV-I associated myelopathy in a Seychellois immigrant.

OBJECTIVE: To describe the clinical and laboratory features of human T-lymphotropic virus type I (HTLV-I) associated myelopathy in an immigrant from the Seychelles. CLINICAL FEATURES: A slowly progressive myelopathy has been recently diagnosed in a 64-year-old woman who emigrated to Australia from the Seychelles in 1957. Sphincter disturbance and back pain were the first manifestations, followed by gait disturbance. Neurophysiological investigation supported the clinical diagnosis of a myelopathy and radiological investigations revealed no structural cause. Serum antibodies to HTLV-I were detected by enzyme-linked particle agglutination and the presence of antibodies to individual HTLV-I gene products in the serum was confirmed by western blot. The virus was detected in a culture of the patient's peripheral blood mononuclear cells by antigen capture assay and by sequencing a polymerase chain reaction product amplified from the env gene. INTERVENTION AND OUTCOME: The patient was advised of the nature and prognosis of her illness. Oral corticosteroids were tried without benefit. CONCLUSIONS: The prevalence of HTLV-I infection is low in Australia although it may be endemic in some Aboriginal communities. Most infections are asymptomatic but the chronic neurological disease associated with HTLV-I infection has now been shown to exist in this country. HTLV-I infection should be considered in the aetiology of myelopathy without another obvious cause.

Australia↗
PubMed1993

Occupational exposure to the human immunodeficiency virus and other blood-borne pathogens. A six-year prospective study.

OBJECTIVE: To prospectively study occupational exposures to human immunodeficiency virus (HIV) and other blood-borne pathogens. DESIGN AND SETTING: Detailed clinical information was collected and follow-up was performed on all health care workers with occupational exposures to potentially infected substances at Fairfield Infectious Diseases Hospital during the period January 1985 to September 1991. RESULTS: There were 230 occupational exposures reported. One hundred and forty-one were considered "significant" or "potentially significant"; these involved exposure (or the potential for exposure) to blood or body fluids by the parenteral route or contamination of non-intact skin or mucous membranes. Needle/syringe assemblies accounted for 59% of the "significant" injuries, "butterfly" needles for 21% and lancets for 8%. "Butterfly" needles were over-represented relative to their degree of use. Seventy-seven of the 230 exposures were HIV-related and 27 of these were considered "significant". The number of HIV positive patients attending the hospital increased progressively over the survey period but the rate of HIV-related exposures fell during that time. After 1988, 13 individuals with "significant" exposure to HIV received a six-week prophylactic course of zidovudine. No health care workers seroconverted for HIV, hepatitis B or hepatitis C during the survey period. CONCLUSIONS: The risk of acquiring HIV (and other blood-borne diseases) through occupational exposure is very low and this risk can be further reduced by adopting safe work practices.

Blood↗
PubMed1993

A comparison of the performance of nine commercially available anti-HTLV-I screening assays.

The performance of eight anti-HTLV-I enzyme immunoassays (EIAs) and one particle agglutination assay was compared with respect to sensitivity, specificity and delta values, by testing a panel containing 99 anti-HTLV-I positive and 126 anti-HTLV-I negative samples which had been characterised by western blot and some by radioimmunoprecipitation assay. The estimated sensitivities produced by these assays ranged between 99% and 100% and estimated specificities were between 95.2% and 100%. The performance of the EIAs was further differentiated by using the delta value which measures the ability of an assay to separate the positive and negative populations from the cutoff value. A delta value could not be calculated for the particle agglutination assay (Serodia) because the test readings were not quantitative. The EIAs most likely to correctly identify anti-HTLV-I positive and anti-HTLV-I negative samples included the Cambridge Biotech, Dupont, Genetic Systems and Olympus assays. Our findings suggest that there may be some difficulty in correctly identifying anti-HTLV-I negative samples using the Abbott, Cellular Products Incorporated (CPI), Coulter and Diagnostic Biotechnology assays. The Serodia assay produced comparable sensitivity and specificity to the eight EIAs.

Agglutination Tests↗
PubMed1993

HIV antibody testing in Australia.

Testing for antibody to human immunodeficiency virus (HIV) in Australia is subjected to continual monitoring for ensuring that the performance of tests in the field is reliable and provides accurate data on HIV tests and testing that are unique to Australia.

Australia↗
PubMed1992

Identification of infection of an Australian resident with the human immunodeficiency virus type 2 (HIV-2).

OBJECTIVE: To present the first confirmed case of human immunodeficiency virus infection type 2 (HIV-2) in an Australian resident. CLINICAL FEATURES: HIV-2 infection in a west African man resident in Sydney was diagnosed in 1992 at Westmead Hospital, Sydney, by serological testing. He was asymptomatic and the blood CD4 T-lymphocyte concentration was not significantly reduced. Infection was probably acquired before migration to Australia. The patient was initially tested for HIV-1 antibody as part of an application for permanent residency. He was in no obvious risk group or transmission category. His serum was repeatedly positive by Genetic Systems enzyme immunoassay (EIA) and borderline by Abbott EIA, was reactive to the HIV-2 peptide on a synthetic envelope peptide assay, and was strongly reactive to all HIV-2 specific viral protein bands on an HIV-2 western blot test. HIV-2 was isolated by co-cultivation of the patient's peripheral blood mononuclear cells and identified by hybridisation using HIV-2 specific oligonucleotide probes, with further confirmation by polymerase chain reaction. INTERVENTION AND OUTCOME: The patient was counselled regarding the clinical course and prognosis of HIV-2 infection, the possible indications for zidovudine therapy, modes of transmission of the virus and safer sex precautions. CONCLUSIONS: This is the first documented case of HIV-2 infection diagnosed in Australia and raises the possibility of other undetected cases. The cost effectiveness of general testing for HIV-2 needs to be assessed and formal epidemiological sentinel programs should be established to monitor specific Australian populations.

AIDS Serodiagnosis↗
PubMed1992

Anti-HIV-1 testing results are reported rapidly by Australian laboratories: a national survey.

The National HIV Reference Laboratory undertook a one-week prospective study to determine the time taken by Australian human immunodeficiency virus antibody (anti-HIV) testing laboratories to test a sample and report an anti-HIV-1 result. The study showed that more than 86% of the sample results were reported by the second day and more than 98% by the fourth day after receipt of the specimen.

Australia↗
PubMed1992

Long-term administration of m-chlorophenylpiperazine (mCPP) to rats induces changes in serotonin receptor binding, dopamine levels and locomotor activity without altering prolactin and corticosterone secretion.

Meta-chlorophenylpiperazine (mCPP) is a serotonin (5-HT) agonist with antidepressant actions. In order to investigate the effects of chronic mCPP treatment the drug was administered to rats for 15 days (5 mg/kg twice daily). Controls were administered saline. Long-term mCPP treatment led to a 36% increase in [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT) binding to 5-HT1a receptors in hippocampus and a 74% decrease in [3H]ketanserin binding to 5-HT2 receptors in cortex, while (-)[125I]iodocyanopindolol ([125I]CYP) binding to 5-HT1b receptors in hypothalamus and striatum was unchanged. In hypothalamus, chronic mCPP treatment decreased the levels of dopamine (DA) but not 5-HT. The usual suppression of locomotor activity induced by acute mCPP administration was less after long-term mCPP treatment. Brain and plasma levels of mCPP following an acute dose were not different between controls and rats previously administered mCPP, suggesting that altered rate of metabolism of the drug did not explain the tolerance to the mCPP-induced decrease in locomotor activity. mCPP-induced prolactin (PRL) and corticosterone release were not changed by previous long-term mCPP administration. Thus, chronic mCPP administration to rats induced alterations in density of 5-HT receptor subtypes, hypothalamic levels of DA and locomotor behavior.

Animals↗