The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Mirella Ezban - One of the best experts on this subject based on the ideXlab platform.
-
qualification of a select one stage activated partial thromboplastin time based clotting assay and two chromogenic assays for the post administration monitoring of nonacog beta pegol
Journal of Thrombosis and Haemostasis, 2017Co-Authors: S Tiefenbacher, S Rosen, R Bohra, J Amiral, Annette E Bowyer, S Kitchen, A Lochu, Mirella EzbanAbstract:Essentials Nonacog beta pegol (N9-GP) is an extended half-life, recombinant human factor IX (FIX). One-stage clotting (OSC) and chromogenic FIX activity assays were assessed for N9-GP recovery. OSC STA®-Cephascreen®, ROX FIX and BIOPHEN FIX chromogenic assays were qualified for N9-GP. Other extended half-life factor products should be assessed in a similar way prior to approval. SummaryBackground Nonacog beta pegol (N9-GP) is an extended half-life, glycoPEGylated recombinant human factor IX that is under development for the prophylaxis and treatment of bleeding episodes in hemophilia B patients. Considerable reagent-dependent variability has been observed when one-stage clotting assays are used to measure the recovery of recombinant FIX products, including N9-GP. Objective To qualify select one-stage clotting and chromogenic FIX activity assays for measuring N9-GP recovery. Methods The accuracy and precision of the one-stage clotting assay (with the STA-Cephascreen activated partial thromboplastin [APTT] reagent) and the ROX Factor IX and BIOPHEN Factor IX chromogenic assays for measuring N9-GP recovery were assessed in N9-GP-spiked hemophilia B plasma samples in a systematic manner at three independent sites, with manufacturer-recommended protocols and/or site-specific assay setups, including different instruments. Results For each of the three FIX activity assays qualified on five different reagent–instrument systems, acceptable intra-assay and interassay accuracy and precision, dilution integrity, reagent robustness and freeze–thaw and short-term sample stabilities were demonstrated. The STA-Cephascreen assay showed a limited reportable range at one of the three qualification sites, and the BIOPHEN Factor IX assay showed suspect low-end sensitivity at one of the three qualification sites. An individual laboratory would account for these limitations by adjusting the assay's reportable range; thus, these findings are not considered to impact the respective assay qualifications. Conclusion The one-stage clotting assay with the STA-Cephascreen APTT reagent, the ROX Factor IX chromogenic assay and the BIOPHEN Factor IX chromogenic assay are considered to be qualified for the measurement of N9-GP in 3.2% (0.109 m) citrated human plasma.
-
qualification of a select one stage activated partial thromboplastin time based clotting assay and two chromogenic assays for the post administration monitoring of nonacog beta pegol
Journal of Thrombosis and Haemostasis, 2017Co-Authors: S Tiefenbacher, S Rosen, R Bohra, J Amiral, Annette E Bowyer, S Kitchen, A Lochu, Mirella EzbanAbstract:Essentials Nonacog beta pegol (N9-GP) is an extended half-life, recombinant human factor IX (FIX). One-stage clotting (OSC) and chromogenic FIX activity assays were assessed for N9-GP recovery. OSC STA®-Cephascreen®, ROX FIX and BIOPHEN FIX chromogenic assays were qualified for N9-GP. Other extended half-life factor products should be assessed in a similar way prior to approval. SummaryBackground Nonacog beta pegol (N9-GP) is an extended half-life, glycoPEGylated recombinant human factor IX that is under development for the prophylaxis and treatment of bleeding episodes in hemophilia B patients. Considerable reagent-dependent variability has been observed when one-stage clotting assays are used to measure the recovery of recombinant FIX products, including N9-GP. Objective To qualify select one-stage clotting and chromogenic FIX activity assays for measuring N9-GP recovery. Methods The accuracy and precision of the one-stage clotting assay (with the STA-Cephascreen activated partial thromboplastin [APTT] reagent) and the ROX Factor IX and BIOPHEN Factor IX chromogenic assays for measuring N9-GP recovery were assessed in N9-GP-spiked hemophilia B plasma samples in a systematic manner at three independent sites, with manufacturer-recommended protocols and/or site-specific assay setups, including different instruments. Results For each of the three FIX activity assays qualified on five different reagent–instrument systems, acceptable intra-assay and interassay accuracy and precision, dilution integrity, reagent robustness and freeze–thaw and short-term sample stabilities were demonstrated. The STA-Cephascreen assay showed a limited reportable range at one of the three qualification sites, and the BIOPHEN Factor IX assay showed suspect low-end sensitivity at one of the three qualification sites. An individual laboratory would account for these limitations by adjusting the assay's reportable range; thus, these findings are not considered to impact the respective assay qualifications. Conclusion The one-stage clotting assay with the STA-Cephascreen APTT reagent, the ROX Factor IX chromogenic assay and the BIOPHEN Factor IX chromogenic assay are considered to be qualified for the measurement of N9-GP in 3.2% (0.109 m) citrated human plasma.
-
international comparative field study of n8 evaluating factor viii assay performance
Haemophilia, 2011Co-Authors: Dorthe Viuff, T W Barrowcliffe, Mirella Ezban, T Saugstrup, David LillicrapAbstract:Discrepancies between the one-stage clotting assay and the chromogenic method, and also among different variations of each method, have been a significant challenge for one B-domain deleted FVIII product. N8 is a B-domain truncated FVIII product developed by Novo Nordisk. The comparison of N8 and Advate(®) was performed in an international, multicentre, randomized and blinded field study of simulated postinfusion samples. Overall, Advate(®) and N8 performed similarly in the one-stage assay. In the one-stage clotting assay, the measured mean FVIII levels of Advate(®) vs. N8 were 0.046/0.047, 0.24/0.24, 0.58/0.60 and 0.82/0.83 IU mL(-1) for the target values of 0.03, 0.2, 0.6 and 0.9 IU mL(-1) , respectively. In the chromogenic assays, the concentration estimates showed a tendency towards higher N8 values as compared with Advate(®) ; the measured FVIII levels of Advate(®) vs. N8 were 0.030/0.032, 0.22/0.24, 0.65/0.74 and 0.98/1.08 IU mL(-1) for the target values of 0.03, 0.2, 0.6 and 0.9 IU mL(-1) , respectively. In the one-stage assays, the measured values were above 150% of target at the lowest concentration, decreasing to around 90% of target at the highest concentration. In contrast, the chromogenic assays were close to target at the lowest concentration and consistently above target at the three highest concentrations. Therefore, the ratio of chromogenic/one-stage potencies was concentration dependent, ranging from 0.66 to 1.30. The SSC plasma standard was similar in both. Assay variability was similar for both compounds. The results show that N8 can be reliably measured in plasma without the need for a separate N8 standard.
Jan Jacobs - One of the best experts on this subject based on the ideXlab platform.
-
chromogenic media for the detection of salmonella enterica serovar paratyphi a in human stool samples evaluation in a reference setting
European Journal of Clinical Microbiology & Infectious Diseases, 2018Co-Authors: Jan Jacobs, Laura Maria Francisca Kuijpers, Annelies PostAbstract:Detection of Salmonella Paratyphi A stool carriers by conventional stool culture media is hindered by the absence of hydrogen sulphide production compared to most other Salmonella serovars. This study evaluated the detection of Salmonella Paratyphi A in stool samples using Salmonella chromogenic media compared to a conventional medium. Four chromogenic media, COMPASS Salmonella agar (Biokar Diagnostics, Beauvais, France), BBL™ CHROMagar™ Salmonella (BD Diagnostics, Erembodegem-Aalst, Belgium), Brilliance™ Salmonella agar (Oxoid Ltd., Basingstoke, UK) and Salmonella PLUS CHROMagar™ (CHROMagar, Paris, France), were compared to conventional Salmonella-Shigella agar (Oxoid Ltd.). The colony morphology of 29 freshly grown stock isolates (Salmonella and competing organisms) was assessed. The limit of detection (LOD) was also determined using saline and stool suspensions. Finally, recognizability of Salmonella Paratyphi A isolates was assessed using 20 human stool samples spiked with different concentrations of Salmonella Paratyphi A. All Salmonella Paratyphi A isolates demonstrated detectable growth with typical purple-coloured colonies that could be clearly differentiated from competing organisms on all four chromogenic media. The LOD for Salmonella Paratyphi A was 103 colony-forming units (CFU)/ml for all media, except for Brilliance agar (105 CFU/ml of stool). Salmonella Paratyphi A was easy to differentiate from competing organisms in the spiked stool samples. Colony yields improved when an enrichment step (Selenite-F broth (BD Diagnostics, Erembodegem-Aalst, Belgium)) and prolonged incubation for 48 h were performed. Chromogenic media demonstrated good specificity and a low LOD for the detection of Salmonella Paratyphi A in stool samples.
S Tiefenbacher - One of the best experts on this subject based on the ideXlab platform.
-
qualification of a select one stage activated partial thromboplastin time based clotting assay and two chromogenic assays for the post administration monitoring of nonacog beta pegol
Journal of Thrombosis and Haemostasis, 2017Co-Authors: S Tiefenbacher, S Rosen, R Bohra, J Amiral, Annette E Bowyer, S Kitchen, A Lochu, Mirella EzbanAbstract:Essentials Nonacog beta pegol (N9-GP) is an extended half-life, recombinant human factor IX (FIX). One-stage clotting (OSC) and chromogenic FIX activity assays were assessed for N9-GP recovery. OSC STA®-Cephascreen®, ROX FIX and BIOPHEN FIX chromogenic assays were qualified for N9-GP. Other extended half-life factor products should be assessed in a similar way prior to approval. SummaryBackground Nonacog beta pegol (N9-GP) is an extended half-life, glycoPEGylated recombinant human factor IX that is under development for the prophylaxis and treatment of bleeding episodes in hemophilia B patients. Considerable reagent-dependent variability has been observed when one-stage clotting assays are used to measure the recovery of recombinant FIX products, including N9-GP. Objective To qualify select one-stage clotting and chromogenic FIX activity assays for measuring N9-GP recovery. Methods The accuracy and precision of the one-stage clotting assay (with the STA-Cephascreen activated partial thromboplastin [APTT] reagent) and the ROX Factor IX and BIOPHEN Factor IX chromogenic assays for measuring N9-GP recovery were assessed in N9-GP-spiked hemophilia B plasma samples in a systematic manner at three independent sites, with manufacturer-recommended protocols and/or site-specific assay setups, including different instruments. Results For each of the three FIX activity assays qualified on five different reagent–instrument systems, acceptable intra-assay and interassay accuracy and precision, dilution integrity, reagent robustness and freeze–thaw and short-term sample stabilities were demonstrated. The STA-Cephascreen assay showed a limited reportable range at one of the three qualification sites, and the BIOPHEN Factor IX assay showed suspect low-end sensitivity at one of the three qualification sites. An individual laboratory would account for these limitations by adjusting the assay's reportable range; thus, these findings are not considered to impact the respective assay qualifications. Conclusion The one-stage clotting assay with the STA-Cephascreen APTT reagent, the ROX Factor IX chromogenic assay and the BIOPHEN Factor IX chromogenic assay are considered to be qualified for the measurement of N9-GP in 3.2% (0.109 m) citrated human plasma.
-
qualification of a select one stage activated partial thromboplastin time based clotting assay and two chromogenic assays for the post administration monitoring of nonacog beta pegol
Journal of Thrombosis and Haemostasis, 2017Co-Authors: S Tiefenbacher, S Rosen, R Bohra, J Amiral, Annette E Bowyer, S Kitchen, A Lochu, Mirella EzbanAbstract:Essentials Nonacog beta pegol (N9-GP) is an extended half-life, recombinant human factor IX (FIX). One-stage clotting (OSC) and chromogenic FIX activity assays were assessed for N9-GP recovery. OSC STA®-Cephascreen®, ROX FIX and BIOPHEN FIX chromogenic assays were qualified for N9-GP. Other extended half-life factor products should be assessed in a similar way prior to approval. SummaryBackground Nonacog beta pegol (N9-GP) is an extended half-life, glycoPEGylated recombinant human factor IX that is under development for the prophylaxis and treatment of bleeding episodes in hemophilia B patients. Considerable reagent-dependent variability has been observed when one-stage clotting assays are used to measure the recovery of recombinant FIX products, including N9-GP. Objective To qualify select one-stage clotting and chromogenic FIX activity assays for measuring N9-GP recovery. Methods The accuracy and precision of the one-stage clotting assay (with the STA-Cephascreen activated partial thromboplastin [APTT] reagent) and the ROX Factor IX and BIOPHEN Factor IX chromogenic assays for measuring N9-GP recovery were assessed in N9-GP-spiked hemophilia B plasma samples in a systematic manner at three independent sites, with manufacturer-recommended protocols and/or site-specific assay setups, including different instruments. Results For each of the three FIX activity assays qualified on five different reagent–instrument systems, acceptable intra-assay and interassay accuracy and precision, dilution integrity, reagent robustness and freeze–thaw and short-term sample stabilities were demonstrated. The STA-Cephascreen assay showed a limited reportable range at one of the three qualification sites, and the BIOPHEN Factor IX assay showed suspect low-end sensitivity at one of the three qualification sites. An individual laboratory would account for these limitations by adjusting the assay's reportable range; thus, these findings are not considered to impact the respective assay qualifications. Conclusion The one-stage clotting assay with the STA-Cephascreen APTT reagent, the ROX Factor IX chromogenic assay and the BIOPHEN Factor IX chromogenic assay are considered to be qualified for the measurement of N9-GP in 3.2% (0.109 m) citrated human plasma.
Laura Maria Francisca Kuijpers - One of the best experts on this subject based on the ideXlab platform.
-
chromogenic media for the detection of salmonella enterica serovar paratyphi a in human stool samples evaluation in a reference setting
European Journal of Clinical Microbiology & Infectious Diseases, 2018Co-Authors: Jan Jacobs, Laura Maria Francisca Kuijpers, Annelies PostAbstract:Detection of Salmonella Paratyphi A stool carriers by conventional stool culture media is hindered by the absence of hydrogen sulphide production compared to most other Salmonella serovars. This study evaluated the detection of Salmonella Paratyphi A in stool samples using Salmonella chromogenic media compared to a conventional medium. Four chromogenic media, COMPASS Salmonella agar (Biokar Diagnostics, Beauvais, France), BBL™ CHROMagar™ Salmonella (BD Diagnostics, Erembodegem-Aalst, Belgium), Brilliance™ Salmonella agar (Oxoid Ltd., Basingstoke, UK) and Salmonella PLUS CHROMagar™ (CHROMagar, Paris, France), were compared to conventional Salmonella-Shigella agar (Oxoid Ltd.). The colony morphology of 29 freshly grown stock isolates (Salmonella and competing organisms) was assessed. The limit of detection (LOD) was also determined using saline and stool suspensions. Finally, recognizability of Salmonella Paratyphi A isolates was assessed using 20 human stool samples spiked with different concentrations of Salmonella Paratyphi A. All Salmonella Paratyphi A isolates demonstrated detectable growth with typical purple-coloured colonies that could be clearly differentiated from competing organisms on all four chromogenic media. The LOD for Salmonella Paratyphi A was 103 colony-forming units (CFU)/ml for all media, except for Brilliance agar (105 CFU/ml of stool). Salmonella Paratyphi A was easy to differentiate from competing organisms in the spiked stool samples. Colony yields improved when an enrichment step (Selenite-F broth (BD Diagnostics, Erembodegem-Aalst, Belgium)) and prolonged incubation for 48 h were performed. Chromogenic media demonstrated good specificity and a low LOD for the detection of Salmonella Paratyphi A in stool samples.
T W Barrowcliffe - One of the best experts on this subject based on the ideXlab platform.
-
international comparative field study of n8 evaluating factor viii assay performance
Haemophilia, 2011Co-Authors: Dorthe Viuff, T W Barrowcliffe, Mirella Ezban, T Saugstrup, David LillicrapAbstract:Discrepancies between the one-stage clotting assay and the chromogenic method, and also among different variations of each method, have been a significant challenge for one B-domain deleted FVIII product. N8 is a B-domain truncated FVIII product developed by Novo Nordisk. The comparison of N8 and Advate(®) was performed in an international, multicentre, randomized and blinded field study of simulated postinfusion samples. Overall, Advate(®) and N8 performed similarly in the one-stage assay. In the one-stage clotting assay, the measured mean FVIII levels of Advate(®) vs. N8 were 0.046/0.047, 0.24/0.24, 0.58/0.60 and 0.82/0.83 IU mL(-1) for the target values of 0.03, 0.2, 0.6 and 0.9 IU mL(-1) , respectively. In the chromogenic assays, the concentration estimates showed a tendency towards higher N8 values as compared with Advate(®) ; the measured FVIII levels of Advate(®) vs. N8 were 0.030/0.032, 0.22/0.24, 0.65/0.74 and 0.98/1.08 IU mL(-1) for the target values of 0.03, 0.2, 0.6 and 0.9 IU mL(-1) , respectively. In the one-stage assays, the measured values were above 150% of target at the lowest concentration, decreasing to around 90% of target at the highest concentration. In contrast, the chromogenic assays were close to target at the lowest concentration and consistently above target at the three highest concentrations. Therefore, the ratio of chromogenic/one-stage potencies was concentration dependent, ranging from 0.66 to 1.30. The SSC plasma standard was similar in both. Assay variability was similar for both compounds. The results show that N8 can be reliably measured in plasma without the need for a separate N8 standard.
-
coagulation and chromogenic assays of factor viii activity general aspects standardization and recommendations
Seminars in Thrombosis and Hemostasis, 2002Co-Authors: T W Barrowcliffe, S Raut, Dawn Sands, A R HubbardAbstract:Factor VIII (FVIII) is assayed by one-stage and two-stage clotting methods and by chromogenic methods, although the chromogenic method has largely replaced the two-stage clotting assay. Clinical plasma samples are assayed mostly by one-stage assays, but most manufacturers of concentrates use the chromogenic method, which is more precise and is the reference method of the European Pharmacopoeia and the International Society on Thrombosis and Haemostasis (ISTH). For most plasma-derived concentrates, assays against the World Health Organization (WHO) concentrate standard give similar results with the one-stage and chromogenic methods, but for products produced by the "method M" monoclonal antibody process, the one-stage potency is 25 to 30% higher than the chromogenic potency. For full-length recombinant products assayed against a plasma-derived concentrate standard, one-stage potencies are about 10% lower than chromogenic potencies, but for the B-domain deleted recombinant product ReFacto, the discrepancy is larger-from 20 to 50%. These discrepancies emphasize the need for an international methodology for labeling of concentrates. In ex vivo assays of hemophilic plasmas after infusion of concentrates, large discrepancies are found among laboratories and with different assay methods when a plasma standard is used. In most studies, the chromogenic potencies are higher than the one-stage potencies, and the discrepancy is highest for recombinant products. This discrepancy can be largely eliminated by the use of concentrate standards, diluted in FVIII-deficient plasma, to assay postinfusion plasma samples.
-
pharmacokinetic in vivo comparison using 1 stage and chromogenic substrate assays with two formulations of hemofil m
Thrombosis and Haemostasis, 1996Co-Authors: T W Barrowcliffe, Gordon L Bray, A R Hubbard, Geoffrey Kemballcook, Dale Owens, Von Tilberg L, Edward D. Gomperts, P. Lilley, John PasiAbstract:: In a study to demonstrate the safety and pharmacokinetics (half-life and recovery) of two different method M purified AHF (Hemofil-M) concentrates processed in the USA and Spain, two different methods of factor VIII assay (one-stage clotting and chromogenic) have been compared in vivo. The study was a single centre blinded, randomised, crossover study. Twelve patients with severe haemophilia A (VIII:C < 2 u/dl) were divided into two subgroups of six. None had received factor VIII concentrate within 48 h preceding the study. Twenty-four pharmacokinetic studies were performed in the 12 patients. Each subgroup received two different lots of study material (US and Spanish) at a dose of 50 u/kg seven days apart. A second randomisation was nominal potency, high: 1000 u or mid: 500 u per vial. The potency label was a one-stage clotting assay using the mega I standard. A standard pharmacokinetic study was performed over 24 h and each blinded sample was analysed in duplicate by a one-stage clotting (aPTT) and a chromogenic (Chromogenix AB; CS) assay at the Royal Free and NIBSC. Pharmacokinetic modelling was performed. The mean label for Hemofil-M using the chromogenic substrate assay was 79% that using the one stage assay (Mega I standard). The recovery was 17-28% higher measured by chromogenic compared to the clotting assay. Since most clinicians use the clotting assay, potency labelling using the chromogenic assay, will overestimate predicted Hemofil-M recovery by as much as 25%.