About
34
Publications
4,210
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
983
Citations
Publications
Publications (34)
Hepatitis B Virus (HBV) infectivity data were reviewed and the 50% infectious dose (ID 50 ) was reassessed in different HBsAg‐positive infection stages enabling modelling of transfusion‐transmitted (TT)‐HBV infection risk if HBsAg donor screening was replaced by individual donation nucleic acid amplification technology (ID‐NAT). Quantitative HBsAg...
The Common Specifications/EU 2017/746 regulation for market approval of class D in vitro diagnostic devices (IVDs) intended for detection of blood borne viruses requires testing of the International Standard and 10–30 seroconversion panels to demonstrate ‘state of the art’ assay performance. We examined whether these requirements for performance ev...
HBV infectivity data was reviewed and the 50% infectious dose (ID50 ) reassessed in different HBsAg positive infection stages enabling modeling of transfusion transmitted (TT)-HBV infection risk if HBsAg donor screening was replaced by individual donation nucleic acid amplification technology (ID-NAT). Quantitative HBsAg and HBV-DNA assays were per...
We prepared severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) working standards and reference panels from a pool of swab fluid samples before and after inactivation by beta-propiolactone and quantified viral load in nucleic acid amplification technology (NAT) detectable RNA copies/mL using limiting dilution analysis. The following 50% lo...
Background
Human immunodeficiency virus (HIV) and hepatitis B virus (HBV) are endemic in South Africa while hepatitis C virus (HCV) infection is rare. Two nucleic acid amplification technology platforms, the Procleix Ultrio Elite assay on the Panther instrument (Elite) and the cobas MPX assay on the cobas 6800 or 8800 system (MPX), are used worldwi...
The World Health Organization (WHO) recommends the clinical use of a HIV‐1 viral load (VL) threshold level of 1000 copies(cp)/mL in patients on antiretroviral therapy (ART) to distinguish between viral control (VL<1000 cp/mL) and viral failure or poor adherence (VL >1000 cp/mL). The accuracy of five quantitative HIV‐1 RNA assays at this level was c...
Background and objectives:
Comparison of two models for estimating residual transfusion transmission risk by NAT screened window period (WP) donations in South African repeat donors gave identical results for HIV but not for HBV. In order to understand discrepant HBV modelling outcomes, the values of input parameters in three HBV WP risk models we...
Background:
Transcription-mediated amplification assays for HBV DNA detection have transitioned from the Ultrio to the Ultrio Plus assay, which features increased analytic sensitivity due to inclusion of a target enhancer reagent. The impact on HBV detection for different categories of HBV infection has not been fully evaluated.
Study design and...
Background:
If anti-hepatitis B core antibody testing is not mandated blood donors with occult hepatitis B infection (OBI) may transmit hepatitis B virus (HBV) to a recipient in spite of the use of nucleic acid amplification technology (NAT) or pathogen inactivation (PI).
Study design and methods:
We developed a model to estimate OBI transmissio...
The Ultrio Elite assay (Hologic/Grifols) runs on the Panther blood screening system and is comparable to the Ultrio Plus assay apart from the addition of oligonucleotides for human immunodeficiency virus Type 2 (HIV-2) detection. In this multicenter evaluation study the analytical sensitivity and genotype detection efficiency of the two assay versi...
Hepatitis C virus (HCV) antigen and antibody combination assays have been launched as a cost-effective alternative to nucleic acid testing (NAT) for reducing the antibody-negative window period (WP). Later, a HCV antigen chemiluminescence immunoassay (CLIA) became available.
A panel composed of 337 HCV NAT-yield samples that were characterized for...
Knowledge about the viral load (VL) distributions in different stages of hepatitis C virus (HCV) infection is essential to compare the efficacy of serologic screening and nucleic acid testing (NAT) in preventing transfusion transmission risk. We studied HCV-RNA levels in Egyptian blood donors in the preseroconversion window period (WP) and in later...
Sensitivity data from a head-to-head comparison study in South Africa were used to compare the efficacy of the Ultrio Plus assay in individual-donation (ID) and minipool (MP)4 and MP8 formats with that of TaqScreen MP6 in preventing hepatitis B virus (HBV) transmission risk.
The replicate nucleic acid test (NAT) results on 106 HBV NAT (Ultrio)-yiel...
Background
Several comparison studies showed that the Ultrio assay (Novartis Diagnostics) used in individual-donation nucleic acid amplification testing (ID-NAT) format was as sensitive as the TaqScreen assay (Roche) on minipools of six donations (MP6), but the sensitivity of HBV DNA detection has been improved in the new Ultrio Plus version of the...
Background
The second triplex transcription-mediated amplification (TMA) assay version (Ultrio Plus, Novartis Diagnostics) uses an additional reagent enhancing the disruption of hepatitisB virus (HBV) particles and release of DNA for the target capture probe. This study compares the performance of this new assay version with the previous one (Ultri...
Background
After 3years of individual-donation nucleic acid test (ID-NAT) screening by the South African National Blood Service (SANBS), a repository of 73 human immunodeficiency virus antibody (anti-HIV)-negative window period (WP)-yield samples and 28 anti-HIV-positive, HIV-RNA-negative elite controllers (ECs) became available for comparison of a...
In minipool nucleic acid test (MP-NAT) screening protocols, the donations implicated in reactive test pools are released for transfusion when they are nonreactive in a repeat test on the individual samples, but in individual-donation (ID)-NAT screening algorithms the release of nonrepeatable reactive (NRR) donations is under discussion.
A previousl...
Accurate determination of the infectious window period (IWP) that remains with individual-donation (ID) or minipool (MP) NAT compared to those with serology assays is essential for residual risk estimations.
The relative sensitivity of the Procleix Tigris system (Gen-Probe/Chiron) used in ID-NAT format and cobas s 201 (Roche Molecular Systems) appl...
To investigate whether it is appropriate to assume comparability of hepatitis virus C (HCV)-RNA results across laboratories in multi-centre studies, nine laboratories of the European Paediatric HCV Network participated in an international proficiency study of HCV-RNA assays. A panel of 12 samples of different dilutions and genotypes was sent to eac...
Routine HCV NAT minipool screening (48 donations) of all blood donations was implemented in July 1999 and was combined with HIV NAT in November 2000. This report describes the validation of the NAT methods and the results of quality control testing.
Nucleic acid was extracted from 2-mL plasma samples by using an automated silica-based extraction me...
Background:
The FDA requirement for sensitivity of viral NAT methods used in blood screening is a 95-percent detection limit of 100 copies per mL, whereas the NAT screening system should have a sensitivity of at least 5000 copies per mL per individual donation. According to the Common Technical Specifications of the European Directive 98/79/EC for...
Blood transfusion centers around the world have introduced minipool NAT to reduce the risk of HBV, HCV, and HIV transmission by blood donations drawn in the infectious window phase. What would be the reduction in the residual risk when minipool NAT would be replaced by single-donation NAT?
A mathematic model was developed to estimate the probabilit...
The European Medicine Evaluation Agency (EMEA) and the European Pharmacopoeia (EP) intend to prescribe HCV RNA testing of plasma pools, with a required assay detection limit of 100 International Units per milliliter (IU/ml). The feasibility of this requirement was examined in the international Viral Quality Control (VQC) programme. In this collabor...
The European Medicine Evaluation Agency (EMEA) and the European Pharmacopoeia (EP) intend to prescribe HCV RNA testing of plasma pools, with a required assay detection limit of 100 International Units per milliliter (IU/ml). The feasibility of this requirement was examined in the international Viral Qualify Control (VQC) programme. In this collabor...
Human parvovirus B19 is a potential risk to hemophiliac patients receiving blood products.
To determine the prevalence of the corresponding antibody in patients with hemophilia A or B von Willebrand's disease, we tested 326 hemophilia patients for anti-B19 IgG. The results were compared with those of 203 age-matched controls (male blood donors and...
Recently, clotting factor preparations transmitted hepatitis A virus (HAV) to hemophilia patients. To study the risk of HAV infection in Dutch hemophilia patients, serum samples of 341 patients with hemophilia were tested for HAV antibodies (anti-HAV).
197/341 patients (group 1) were treated with clotting factor concentrates produced from large pla...
Serum samples from 316 patients visiting the Dutch National Hemophilia Center were collected from 1979 to 1993 and stored at −30°C. Patients were placed into three different groups: (1) patients ever treated with large pool non-hepatitis C virus (HCV)-safe concentrate (n=179); (2) patients treated with cryoprecipitate (n = 125); and (3) patients tr...
To establish the value of the second-generation recombinant immunoblot assay (RIBA-2) and cDNA polymerase chain reaction (cDNA PCR) for confirmation of hepatitis C virus (HCV) infection, anti-HCV reaction patterns and the presence of HCV RNA were examined in 610 blood donors and 255 non-A, non-B hepatitis patients who were positive or indeterminate...
