R E Gaines Das

National Institute for Biological Standards and Control, Potters Bar, England, United Kingdom

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Publications (99)264.17 Total impact

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    ABSTRACT: Whole-cell pertussis vaccines are still widely used across the globe and have been shown to produce longer lasting immunity against pertussis infection than acellular pertussis vaccines. Therefore, whole-cell vaccines are likely to continue to be used for the foreseeable future. The intracerebral mouse protection test (Kendrick test) is effective for determining the potency of whole-cell pertussis vaccines and is the only test that has shown a correlation with protection in children. Here we review the Kendrick test in terms of international requirements for vaccine potency and critical technical points to be considered for a successful test including test validity, in-house references and statistical analysis. There are objections to the Kendrick test on animal welfare and technical grounds. Respiratory challenge assays, nitric oxide induction assay and serological assays have been developed and have been proposed as possible methods which might provide alternatives to the Kendrick test. These methods and their limitations are also briefly discussed. Establishment of validated in vitro correlates of protection has yet to be achieved. New technical developments, such as genome sequence and the use of gene microarrays to screen responses triggered by vaccine components may also provide leads to alternative assays to the Kendrick test by identifying biomarkers of protection.
    Expert Review of Vaccines 09/2014; · 4.22 Impact Factor
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    ABSTRACT: Speculation that the Japanese modified intra-cerebral challenge assay, which is used in several countries for control of acellular pertussis vaccines, depends on the presence of small amounts of active pertussis toxin led to an assumption that it may not be appropriate for highly toxoided or genetically detoxified vaccines. Consequently, at the recommendation of a World Health Organisation AD Hoc Working Group on mouse protection models for testing and control of acellular pertussis vaccine, the effect of pertussis toxin on the modified intra-cerebral challenge assay (modified Kendrick, MICA) was evaluated in an international collaborative study. Results of this study showed that for genetically detoxified vaccines both with and without active pertussis toxin the MICA clearly distinguished mice vaccinated with acellular vaccines from unvaccinated mice and gave a significant dose–response relationship. However, vaccine samples containing active pertussis toxin (5 or 50 ng/single human dose) appeared to be more potent than the equivalent sample without active pertussis toxin. Similar results were also given by two respiratory infection models (intranasal and aerosol) included in the study. The results also indicated that the effect of pertussis toxin may vary depending on mouse strain.
    Biologicals 01/2013; · 1.62 Impact Factor
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    ABSTRACT: Whole cell pertussis vaccine is still widely used in many countries. An International Standard is needed for its potency control. The Third International Standard for Pertussis Vaccine was prepared about 40 years ago and its replacement was recommended by the Expert Committee for Biological Standardisation (ECBS) of the WHO. Material in ampoules coded 94/532 was prepared as a candidate replacement and has been evaluated in international collaborative studies which consisted of two parts. The first part, to assess the suitability of the candidate standard by comparing it with the Second International Standard for Pertussis Vaccine (IS2) involved 14 laboratories in 11 countries. The second part to compare the candidate standard with the Third International Standard for Pertussis Vaccine (IS3) involved 16 laboratories in 14 countries. Since 1995 various other studies have included the international standards and the results of these are also considered in assessing likely continuity of the IU for potency of whole cell pertussis vaccine. The preparation in ampoules coded 94/532 was adopted by the WHO ECBS in October 2006 as the 4th International Standard for whole cell pertussis vaccine and assigned an activity of 40 IU per ampoule on the basis of the studies reported here.
    Biologicals 11/2010; 38(6):644-51. · 1.62 Impact Factor
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    ABSTRACT: This report reflects the discussion and conclusions of a WHO group of experts from National Regulatory Authorities (NRAs), National Control Laboratories (NCLs), vaccine industries and other relevant institutions involved in standardization and control of diphtheria, tetanus and pertussis vaccines (DTP), held on 20-21 July 2006 and 28-30 March 2007, in Geneva Switzerland for the revision of WHO Manual for quality control of DTP vaccines. Taking into account recent developments and standardization in quality control methods and the revision of WHO recommendations for D, T, P vaccines, and a need for updating the manual has been recognized. In these two meetings the current situation of quality control methods in terms of potency, safety and identity tests for DTP vaccines and statistical analysis of data were reviewed. Based on the WHO recommendations and recent validation of testing methods, the content of current manual were reviewed and discussed. The group agreed that the principles to be observed in selecting methods included identifying those critical for assuring safety, efficacy and quality and which were consistent with WHO recommendations/requirements. Methods that were well recognized but not yet included in current Recommendations should be taken into account. These would include in vivo and/or in vitro methods for determining potency, safety testing and identity. The statistical analysis of the data should be revised and updated. It was noted that the mouse based assays for toxoid potency were still quite widely used and it was desirable to establish appropriate standards for these to enable the results to be related to the standard guinea pig assays. The working group was met again to review the first drafts and to input further suggestions or amendments to the contributions of the drafting groups. The revised manual was to be finalized and published by WHO.
    Vaccine 05/2008; 26(16):1913-21. · 3.49 Impact Factor
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    ABSTRACT: In November 2005, the World Health Organization convened an informal technical workshop on the stability of reference materials for biological medicines and in vitro diagnostics. The meeting was attended by experts from WHO collaborating centres in the area of biological standardization, national control laboratories, industries and other relevant organizations. The consultation group discussed current practices and approaches to predicting and monitoring the stability of biological reference materials. The group agreed to the need for establishing a working group (i) to continue dialogue on potential issues encompassing the principles, strategies and practicality for assuring the stability of WHO international reference standards for biological medicines and in vitro diagnostics and (ii) to develop more detailed guidance for assessment of the stability of WHO international biological reference materials.
    Biologicals 11/2007; 35(4):361-5. · 1.62 Impact Factor
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    ABSTRACT: A study was performed to investigate the reproducibility of haemagglutinin-inhibition (HI) and virus neutralising (VN) assays for detection of anti-influenza antibody. Participants in 11 laboratories from eight countries measured antibody to egg-grown A/Japan/434/2003, cell-grown A/Japan/434/2003 and A/Panama/2007/99 (H3N2) viruses in 18 human and two post-infection ferret sera. There was significant intra-laboratory assay variability for VN compared to HI. For replicate assays within laboratories, 14/410 (3%) and 130/631 (21%) titres differed by >2-fold (p<0.0001), and 0/410 (0%) and 35/631 (6%) titres differed by >5-fold (p<0.0001) by HI and VN, respectively. Although both assays showed inter-laboratory variation, VN assays were significantly more variable than HI. Median geometric coefficients of variation (GCV) for VN assays with each virus were 256%, 323% and 359% compared to 138%, 155% and 261% with HI. A serum standard improved inter-laboratory agreement and reduced median GCVs. This study raises concern about comparability of serology results from H5N1 vaccine trials and it is proposed that an International Standard for influenza H5N1 antibody is developed.
    Vaccine 05/2007; 25(20):4056-63. · 3.49 Impact Factor
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    ABSTRACT: A World Health Organization requirement for biological standards is that they should exhibit long-term stability at their recommended storage temperature. Thermal stability is usually predicted in accelerated thermal degradation studies, where ampoules of the lyophilized standard are stored at elevated temperatures for relatively short times before testing. To confirm the predicted thermal stability of the 2nd international standard of human interferon alpha 2b (IFN-alpha2b; 95/566), we tested the potency of the ampouled contents of this standard after 9 years storage at the customary storage temperature of -20 degrees C in comparison with ampoules of the IS which had been stored continuously at temperatures ranging from -150 degrees C to 56 degrees C. Since IFN-alpha2b potency estimates derived from the results of antiviral assays (AVA) showed high within-assay variability, we investigated a novel reporter gene assay (RGA) based on induction of secreted alkaline phosphatase (SEAP) for comparability and precision of such estimations. We show that this RGA generated comparable estimates with overall lower variation. Additionally, the SEAP conversion of p-nitrophenyl phosphate to yellow product could be followed kinetically. Absorbance readings were shown to increase with time in proportion with increasing concentration of IFN-alpha2b. When the time-dependent increments of absorbance were plotted graphically, the slopes of lines corresponded to concentration. This approach enabled single dilutions of IFN samples, identical in molecular structure to an IFN-alpha2b standard, to be used for potency estimates by interpolation of slope value against those of the standard at fixed concentrations. It appears attractive for high through-put potency testing of various R&D IFN-alpha2b samples.
    Journal of Immunological Methods 02/2007; 319(1-2):6-12. · 2.23 Impact Factor
  • C Jane Robinson, Rose Gaines Das, Pauline Maile
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    ABSTRACT: Preparations of human sequence recombinant keratinocyte growth factor (KGF), fibroblast growth factor-7 (FGF-7) synthesized in E. coli were formulated and lyophilized at National Institute for Biological Standards and Control (NIBSC) and evaluated in a collaborative study using in vitro bioassays and immunoassays. One candidate standard was the full-length mature KGF molecule and the two others were different formulations of a truncated form of the molecule, KGF (24-163). The study demonstrated the difficulty of performing interlaboratory comparison of assays without a common reference standard and differences in dose-response relationships between molecular variants. On the basis of the results reported here, the World Health Organization (WHO) established the preparation coded 03/150 as the WHO reference reagent for human KGF, with an assigned unitage of 4000 units of KGF per ampoule and the preparation coded 03/148 as the WHO reference reagent for human KGF (24-163), with an assigned unitage of 9000 units of KGF(24-163) per ampoule.
    Growth Factors 01/2007; 24(4):279-84. · 2.20 Impact Factor
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    ABSTRACT: Preparations of human sequence recombinant vascular endothelial growth factor-165 (VEGF165) synthesized in Escherichia coli were formulated and lyophilized at NIBSC. Following evaluation at NIBSC, the first preparation, 01/424, has been distributed since 2002 as a NIBSC research reagent, but shows variation between ampoules in the volume and crystalline appearance of the lyophilized plug. A second preparation, 02/286, was subsequently lyophilized in a different formulation. Preparation 02/286 has now been evaluated in a collaborative study for its suitability to serve as a reference standard, and compared with preparation 01/424, by five laboratories using in vitro bioassays or immunoassays. On the basis of the results reported here, the World Health Organization (WHO) established the preparation coded 02/286 as the WHO reference reagent (RR) for human VEGF165, with an assigned unitage of 13,000 units per ampoule.
    Growth Factors 01/2007; 24(4):285-90. · 2.20 Impact Factor
  • Anthony Meager, Rose Gaines Das
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    ABSTRACT: Human interferon beta (IFN-beta) has been developed as a major biotherapeutic agent for the treatment of multiple sclerosis. Since World Health Organization (WHO) international standards (IS) for IFN-beta were established several years prior to the development of clinical grade IFN-beta products, a number of scientific issues with regard to the biological standardisation of natural and recombinant IFN-beta products have emerged. In order to address these issues, an international collaborative study to evaluate WHO IS and candidate international standards (CIS) of IFN-beta was instigated by the National Institute for Biological Standards and Control (NIBSC) in 2000 and was carried out in the succeeding year. Sixteen expert laboratories from 8 countries worldwide participated in the study. They performed titrations on 8 different IFN-beta preparations, including IS and new CIS, in a variety of mainly antiviral- but also including some antiproliferative- and reporter gene-assays, and contributed raw data from these assays to NIBSC for statistical analysis and calculation of potencies. While both intra- and inter-laboratory variation of potency estimates was evident, overall validity of the study as a whole was clearly shown by comparison of two pairs of internal coded duplicates, which gave the expected relative potency of 1 and the lowest inter-laboratory variability of potency estimates in all assay types. The CIS containing Chinese hamster ovary (CHO) cell- or human fibroblast-derived, glycosylated, IFN-beta gave similar low inter-laboratory variation in potency estimates one to another as the coded duplicates, which was significantly less than to the 2nd WHO IS of IFN-beta, human fibroblast-derived, Gb23-902-531. One of these CIS, designated 00/572, containing CHO cell-derived IFN-beta and formulated with both bovine casein and human serum albumin, could be assigned a potency, consistent for all assay types, of 40,000 international units (IU) per ampoule relative to the IU of the 2nd IS of IFN-beta, Gb23-902-531. Other CIS containing glycosylated IFN-beta, either CHO cell- or human-fibroblast-derived, could also be assigned potency values that were continuous with the IU of Gb23-902-531 and 00/572. However, greater inter-laboratory variations in estimates were evident from comparisons of Gb23-902-531 or 00/572 with either the 1st IS for E. coli-derived, non-glycosylated, IFN-beta with serine substitution at position 17 (IFN-beta Ser 17 mutein), Gxb02-901-535, or with a CIS (00/574) containing IFN-beta Ser 17 mutein. Indeed, variations in potency estimates for preparations containing IFN-beta Ser 17 mutein were sufficiently large to indicate that assays could distinguish preparations of IFN-beta Ser 17 mutein from preparations of glycosylated IFN-beta. Thus, neither the 2nd IS of IFN-beta, Gb23-902-531, containing fibroblast-derived IFN-beta, nor CIS, 00/572, containing CHO cell-derived IFN-beta, was appropriate for standardisation of preparations of IFN-beta Ser 17 mutein. Conversely, neither the IS of IFN-beta Ser 17 mutein, Gxb02-901-535, or a CIS of IFN-beta Ser 17 mutein, 00/574, was appropriate for the standardisation of preparations of glycosylated IFN-beta. CIS 00/572, containing CHO cell-derived, glycosylated IFN-beta, was clearly shown to be suitable to serve as a primary standard for glycosylated forms of IFN-beta, especially clinical grade IFN-beta-1a products. It was further shown to exhibit high thermal and long-term stability. Since the CHO cell-derived IFN-beta used for preparation of 00/572 was of a greater purity than the IFN-beta used for the 2nd IS of IFN-beta, Gb23-902-531, it was recommended by the WHO Informal Consultation on the Standardisation of Cytokines, Growth Factors and Other Endocrinological Substances, which met in October 2003, that 00/572 should replace Gb23-902-531 as the IS for glycosylated IFN-beta. This recommendation was accepted by the WHO Expert Committee on Biological Standardization (ECBS) at its annual meeting in November 2003 and 00/572 was established as the 3rd IS for human glycosylated IFN-beta with an assigned potency of 40,000 IU. As this study identified no advantage to replacing the existing 1st IS for IFN-beta Ser 17 mutein, Gxb02-901-535, WHO ECBS accepted that this should continue to serve as the IS for this material.
    Journal of Immunological Methods 12/2005; 306(1-2):1-15. · 2.23 Impact Factor
  • Rose E. Gaines Das
    07/2005; , ISBN: 9780470011812
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    ABSTRACT: Lyophilization is a key strategy in the stabilization of biological materials. Protection of the lyophilized material from an oxidizing atmosphere is essential if stability is to be maintained under long term storage. Vials of lyophilized albumin closed by two methods and ampoules of albumin have been examined for moisture and oxygen ingress after storage both under conditions of stress for two months and under thermally accelerated conditions for one year. The results show that the gas and moisture contents of ampoules do not detectably change even under conditions of stress, in contrast to vials for which this study shows clearly detectable moisture ingress and suggests some oxygen ingress. This is consistent with the results of other studies. Thus, although vials may be satisfactory under constrained conditions of temperature and storage for limited periods of time, and are presently used satisfactorily for some working standards, it would be prudent to continue to use ampoules for storage of international reference materials which are intended for indefinite storage and for which stability is an essential requirement.
    Biologicals 07/2005; 33(2):63-70. · 1.62 Impact Factor
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    ABSTRACT: A freeze-dried human serum preparation containing immunoglobulin G (IgG) to Toxoplasma gondii was assessed for its suitability as an international reference reagent in an international collaborative study by 24 laboratories from 17 countries. This candidate standard was compared with the third international standard (IS) for human anti-Toxoplasma serum, TOXM, with the previous second IS, TOXS, and with a range of other serum samples. Samples were tested with the Sabin-Feldman dye test and a range of agglutination assays and enzyme immunoassays. This study emphasizes the need for appropriate standards if intermethod agreement of estimates is to be achieved. On the basis of the results of this study, the preparation was established by the World Health Organization as the first IS for human anti-Toxoplasma IgG, with an assigned potency of 20 IU per ampoule of total anti-Toxoplasma antibodies.
    Journal of Clinical Microbiology 12/2004; 42(11):5133-8. · 4.07 Impact Factor
  • Rose E Gaines Das
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    ABSTRACT: Any experiment involving the use of animals which is not well-planned, meticulously carried out, and scrupulously analysed, is unethical. Planning, or good experimental design, followed by analysis appropriate for the design, will help to ensure the optimal use of animals. Thus, collaboration between biologist and statistician, especially at the planning and analysis stages, is one of the best ways of achieving an ethical and successful experiment. However, genuine communication is necessary for any collaboration, and this requires time and patience, on the part of both biologist and statistician. Although the three fundamental principles of experimental design, replication, randomisation and local control, are straightforward in theory, there is substantial scope for misunderstanding and misinterpretation in practice. Each experiment presents unique and interacting biological and statistical problems, and both the right design and the correct analysis should be decided on a case-by-case basis.
    Alternatives to laboratory animals: ATLA 10/2004; 32 Suppl 2:5-8. · 1.37 Impact Factor
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    ABSTRACT: An optimised test designed for an in vitro monocyte activation test for pro-inflammatory and pyrogenic contaminants of parenteral drugs is described, together with ways to address the inherent variability of such assays in which cells are cultured using 96-well plates. The test preparation is cultured with peripheral blood mononuclear cells (PBMNC) and the contaminants in the test article stimulate the release from the cells of the endogenous pyrogenic cytokine interleukin-6 (IL-6). The test system is in use within the pharmaceutical industry and at a national control authority for detecting pro-inflammatory and pyrogenic contaminants, including 'rabbit-negative' and 'LAL-negative' non-endotoxin pyrogens. Products tested include small molecules, biologicals and vaccines. The PBMNC/IL-6 monocyte activation test has been approved by the US FDA as an 'end-product release test' and also is being used for in-process testing.
    Journal of Immunological Methods 06/2004; 288(1-2):165-77. · 2.23 Impact Factor
  • Dorothea Sesardic, Tong Leung, Rose Gaines Das
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    ABSTRACT: The biological activity of therapeutic preparations of botulinum type A toxin is currently expressed in units defined on the basis of the median lethal intraperitoneal dose of that preparation in mice at 72 h, the LD50 dose. In this study we describe the comparison, by ten laboratories in five countries, of three different formulations of botulinum type A toxin using the mouse lethality test, and also using the relative activities of the preparations. The results of this study show that use of a standard preparation and expression of relative potency gives substantially greater consistency between and within laboratories than when mouse LD50 unit is used to define activity of botulinum toxin.
    Biologicals 01/2004; 31(4):265-76. · 1.62 Impact Factor
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    ABSTRACT: A rapid, 'one-plate' monocyte-activation test is described for detecting endotoxin and non-endotoxin pyrogens in parenteral medicinal products. The one-plate test offers useful gains over conventional 'two-plate' (cell culture plate+ELISA plate) tests in terms of its limit of detection, robustness, speed and cost. The 'one-plate' test is likely to be applicable to a wide range of products because it allows less time for product interference in the test. The 'one-plate' test utilises pyrogen-free anti-cytokine (interleukin (IL)-6 or tumour necrosis factor alpha (TNFalpha)) antibodies (Ab), coated and stabilised onto (pyrogen-free) 96-well plates. Monocytes/monocytic cells, endotoxin (lipopolysaccharides, LPS) standard or sample and (pyrogen-free) second (labelled) Ab are cultured together (usually for 2-4 h) on the Ab-coated plate and then the plate is washed and the ELISA completed. There is no transfer from one plate to another and no (further) incubations of (released) cytokine with, first, coating Ab and, then, developing Ab since these steps have already taken place during the initial cell culture. The rapid, 'one-plate' test is readily automated. The preferred readout is IL-6, which gives a limit of detection of 0.015 endotoxin units (EU)/ml with peripheral blood mononuclear cell (PBMNC), 0.03 EU/ml with diluted whole blood and 0.05 EU/ml with a monocytic cell line (MONO MAC 6).
    Journal of Immunological Methods 04/2003; 274(1-2):209-20. · 2.23 Impact Factor
  • A Mire-Sluis, R Gaines Das, A Lernmark
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    ABSTRACT: The immunogenicity of biological therapeutic products is currently a high profile regulatory and biotechnology industry issue. The immune responses raised against biotechnology products range from the benign, to affecting product efficacy, to those that have serious deleterious clinical impact. The most widely used marker of immunogenicity is the detection and measurement of antibody responses induced in vivo to a product. This relies on assays that are sensitive and robust. In order to assess the parameters of an assay during its design, development and validation, it is extremely useful to have a reference standard to compare assay results. However, immune responses lead to polyclonal antibody preparations that can vary by affinity and avidity. This makes it extremely difficult to select a preparation that will behave similarly in different test systems and against different antibody samples. The case example of the WHO standardization of islet cell antibodies illustrates the difficulties in the process and the mechanisms required to produce a suitable antibody standard.
    Developments in biologicals 02/2003; 112:153-63.
  • D Xing, R Gaines Das, P Newland, M Corbel
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    ABSTRACT: Pertussis toxin (PT) in its detoxified form is an important antigenic component of both acellular and whole cell pertussis vaccines. Limits on the content of active PT in acellular vaccines are set in official monographs (EP, WHO, USP) and evidence of compliance is therefore, required by regulatory authorities. The two assay methods which are currently used by most manufacturers and official national control laboratories to monitor residual PT activity in acellular pertussis vaccines (and also in whole cell vaccines) are histamine sensitising (HIST) assays and Chinese hamster ovary (CHO) cell assays. Currently, different reference preparations of PT are used by individual laboratories for these tests. We therefore organised an international collaborative study to examine, by these two assay methods, two freeze-dried purified preparations of PT, one preparation in ampoules coded JNIH-5 and one preparation in ampoules coded 90/518, together with in-house reference (IHR) preparations in current use. Data from this study confirm that both JNIH-5 and 90/518 show biological activity both in HIST assays and in CHO-cell assays. Both HSD50 and ED50 values obtained in this study differ significantly between laboratories and thus show that biological activity is not determined by the nominal masses of preparations. Estimates of relative potency of 90/518 in terms of JNIH-5 per ampoule for the HIST assays do not differ significantly between laboratories. The overall mean estimates of relative potency of 90/518 in terms of JNIH-5 do not differ significantly between the two methods. Data from this study further indicate that the biological activity of different preparations was not directly related to their stated protein content. The use of protein content to indicate the level of PT activity in different preparations would give misleading results. Thus, use of a common standard is shown to greatly improve between laboratory agreement of estimates.
    Vaccine 11/2002; 20(29-30):3535-42. · 3.49 Impact Factor
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    ABSTRACT: Two methods for predicting the specific in vivo bioactivity of recombinant follicle stimulating hormone (FSH), based on quantitative measures of isoform distribution by isoelectric focusing (IEF)(1) and by capillary zone electrophoresis (CZE)(2) respectively, have been subjected to an international collaborative study by six laboratories from six countries. Both methods were used to estimate the predicted bioactivities of four preparations of follitropin beta, coded FSH A-D, differing widely in their isoform compositions and specific bioactivities. The mean predicted estimate of potency by IEF and CZE for each FSH preparation by each laboratory was within 80-125% of its potency estimated by bioassay, except for the mean estimates by CZE of that for FSH A by one laboratory and of that of FSH D by another. Each of the six laboratories using the IEF method, and each of the five laboratories using the CZE method were able to rank these FSHs according to their bioactivities, namely FSH B>FSH C>FSH A>FSH D. All laboratories were able to use both IEF and CZE to discriminate between FSH A and C, with bioactivities within 76-132% of one another. Four of six laboratories were able to use IEF, and two of five laboratories were able to use CZE, to discriminate between FSH B and C, with bioactivities within 89-112% of one another. This suggests that the accuracy and precision of both these methods should be sufficient to discriminate between FSHs which would meet or fail European Pharmacopoeia requirements for this type of hormone, since these stipulate that estimates of potency should fall between 80-125% of its stated potency. Using in most cases duplicate estimates in two independent assays, and excluding Laboratory 4, the pooled intra-laboratory geometric coefficient of variation (GCV) was about 4% for both IEF and CZE, and the inter-laboratory GCV was about 7% for IEF and about 10% for CZE. The use of one FSH preparation as a standard, with its specific activity as an assigned value, reduced the inter-laboratory variability of estimates for the remaining FSHs by both methods. This increased the accuracy of the predicted estimates of bioactivity for these remaining FSHs in terms of their approximation to the values for their bioactivities estimated by bioassay. These data therefore suggest that both these methods, and particularly IEF, are sufficiently accurate, precise and robust to be used for predicting the bioactivity of batches of follitropin beta, and especially if used with a standard preparation.
    Biologicals 10/2002; 30(3):217-34. · 1.62 Impact Factor