SMALL SAMPLE SIZE CAPABILITY INDEX FOR ASSESSING VALIDITY OF ANALYTICAL METHODS

peer reviewedaudience: researcher, professional, studentAnalytical method’s capability evaluation can be a useful methodology to assess the fitness of purpose of these methods for their future routine application. However, care on how to compute the capability indices has to be made. Indeed, the commonly used formulas to compute capability indices such as Cpk, will highly overestimate the true capability of the methods. Especially during methods validation or transfer, there are only few experiments performed and, using in these situations the commonly applied capability indices to declare a method as valid or as transferable to a receiving laboratory will conduct to inadequate decisions. In this work, an improved capability index, namely Cpk-tol and the corresponding estimator of proportion of non conforming results (tolCpk−π) is proposed. Through Monte-Carlo simulations, they have been shown to greatly increase the estimation of analytical methods capability in particular in low sample size situations as encountered during methods validation or transfer. Additionally, the usefulness of this capability index is illustrated through several case studies

On the Correlation Between CO Absorption and Far-Ultraviolet Non-Linear Extinction Toward Galactic OB Stars

A sample of 59 sight lines to reddened Galactic OB stars was examined for correlations of the strength of the CO Fourth Positive (A - X) absorption band system with the ultraviolet interstellar extinction curve parameters. We used archival high-dispersion NEWSIPS IUE spectra to measure the CO absorption for comparison to parametric fits of the extinction curves from the literature. A strong correlation with the non-linear far-UV curvature term was found with greater absorption, normalized to E(B-V), being associated with more curvature. A weaker trend with the linear extinction term was also found. Mechanisms for enhancing CO in dust environments exhibiting high non-linear curvature are discussed.Comment: 10 pages, including 6 figures. LaTeX2e (emulateapj5.sty). To appear in ApJ, Sep 20, 200

Towards standardization of RNA quality assessment using user-independent classifiers of microcapillary electrophoresis traces

While it is universally accepted that intact RNA constitutes the best representation of the steady-state of transcription, there is no gold standard to define RNA quality prior to gene expression analysis. In this report, we evaluated the reliability of conventional methods for RNA quality assessment including UV spectroscopy and 28S:18S area ratios, and demonstrated their inconsistency. We then used two new freely available classifiers, the Degradometer and RIN systems, to produce user-independent RNA quality metrics, based on analysis of microcapillary electrophoresis traces. Both provided highly informative and valuable data and the results were found highly correlated, while the RIN system gave more reliable data. The relevance of the RNA quality metrics for assessment of gene expression differences was tested by Q-PCR, revealing a significant decline of the relative expression of genes in RNA samples of disparate quality, while samples of similar, even poor integrity were found highly comparable. We discuss the consequences of these observations to minimize artifactual detection of false positive and negative differential expression due to RNA integrity differences, and propose a scheme for the development of a standard operational procedure, with optional registration of RNA integrity metrics in public repositories of gene expression data

Mise en oeuvre de la simulation numérique dans la conception intégrée de pompes hydrauliques

L'hydraulique de puissance joue un rôle majeur dans l'ensemble des systèmes mécaniques nécessitant des puissances massiques élevées. Son champ d'application s'étend à de nombreux domaines tels que les transports de biens et de personnes, les travaux publics, les machines agricoles ainsi que les machines-outils. L'augmentation du prix de l'énergie, les contraintes environnementales ainsi que les exigences du marché mondial imposent aux fabricants d'équipements hydrauliques de produire des composants toujours plus compétitifs et de plus en plus performants. Face à ces exigences l'innovation est primordiale. La recherche et le développement ayant pour vocation la mise en ?uvre de solutions nouvelles ainsi que la compréhension des phénomènes physiques constituent la véritable pierre angulaire de la discipline. Les générateurs de débits, plus particulièrement les pompes à pistons font l'objet de nombreuses études dans le but d'améliorer leurs performances. Ces dernières sont dédiées à la caractérisation de l'évolution des différents paramètres physiques influencés par les conditions de fonctionnement. Elles concernent également la modélisation de leurs comportements ainsi que l'optimisation de la conception de certains de ses composants. Le développement conventionnel d'une pompe fait appel à la méthode expérimentale essais-erreurs avec itérations successives longues et couteuses. L'intégration de la simulation numérique très en amont permet une optimisation des produits par prototypage virtuel tout en réduisant considérablement le coût et le temps de développement. Le travail mené se situe au carrefour de ces deux méthodes de conception dans le but d'améliorer les performances des pompes hydrauliques à pistons. Il s'agit d'observer de quelle façon est mise à profit l'utilisation de la simulation numérique pour la conception de produits nouveaux. A partir des connaissances relatives aux caractéristiques d'une pompe hydraulique à pistons obtenues lors d'essais physiques, l'objectif est de modéliser le comportement de cette dernière. Ce modèle permet d'identifier les paramètres qui influencent de manière plus ou moins significative les performances de la pompe étudiée. Ces derniers constituent le socle sur lequel un travail d'investigation pourra être mené. Ce travail s'inscrira dans un processus de simulations auquel les plans d'expériences numériques permettront d'aboutir aux configurations optimales d'un nouveau produit

Universal applicability of Total Error for the validation of bioanalytical methods

An innovative universal strategy using Total Error is thus proposed to decide about the method’s validity that controls the risk of accepting an unsuitable assay together with the ability to predict the reliability of future results. Several examples of applications of this validation methodology to various types of assays [LC-MS, ELISA, Bio-Assays] will be presented

Simultaneous improvement of the predictive character of the validation data and estimation of measurement uncertainty

C.I.R.M

COMBINATION OF INDEPENDENT COMPONENT ANALYSIS, DESIGN OF EXPERIMENTS AND DESIGN SPACE FOR A NOVEL METHODOLOGY TO DEVELOP CHROMATOGRAPHIC METHODS

As defined by ICH [1] and FDA, Quality by Design (QbD) stands for “a systematic approach to development that begins with predefined objectives and emphasizes product and process understanding and process control, based on sound science and quality risk management”. A risk–based QbD–compliant approach is proposed for the robust development of analytical methods. This methodology based on Design of Experiments (DoE) to study the experimental domain models the retention times at the beginning, the apex and the end of each peak corresponding to the compounds of a mixture and uses the separation criterion (S) rather than the resolution (RS) as a Critical Quality Attribute. Stepwise multiple linear regressions are used to create the models. The estimated error is propagated from the modelled responses to the separation criterion (S) using Monte Carlo simulations in order to estimate the predictive distribution of the separation criterion (S) over the whole experimental domain. This allows finding ranges of operating conditions that will guarantee a satisfactory quality of the method in its future use. These ranges define the Design Space (DS) of the method. In chromatographic terms, the chromatograms processed at operating conditions within the DS will assuredly show high quality, with well separated peaks and short run time, for instance. This Design Space can thus be defined as the subspace, necessarily encompassed in the experimental domain (i.e. the knowledge space), within which the probability for the criterion to be higher than an advisedly selected threshold is higher than a minimum quality level. Precisely, the DS is defined as “the multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality” [1]. Therefore, this DS defines a region of operating conditions that provide prediction of assurance of quality rather than only quality as obtained with traditional mean response surface optimisation strategies. For instance, in the liquid chromatography there is a great difference in e.g. predicting a resolution (RS) higher than 1.5 vs. predicting that the probability for RS to be higher than 1.5 (i.e. P(RS> 1.5)) is high. The presentation of this global methodology will be illustrated for the robust optimisation and DS definition of several liquid chromatographic methods dedicated to the separation of different mixtures: pharmaceutical formulations, API and impurities/degradation products, plant extracts, separation of enantiomers, … References [1] International Conference on Harmonisation (ICH) of Technical Requirements for Registration of Pharmaceuticals for Human Use, Topic Q8(R2): Pharmaceutical development, Geneva, 2009

A Functional and Regulatory Network Associated with PIP Expression in Human Breast Cancer

BACKGROUND: The PIP (prolactin-inducible protein) gene has been shown to be expressed in breast cancers, with contradictory results concerning its implication. As both the physiological role and the molecular pathways in which PIP is involved are poorly understood, we conducted combined gene expression profiling and network analysis studies on selected breast cancer cell lines presenting distinct PIP expression levels and hormonal receptor status, to explore the functional and regulatory network of PIP co-modulated genes. PRINCIPAL FINDINGS: Microarray analysis allowed identification of genes co-modulated with PIP independently of modulations resulting from hormonal treatment or cell line heterogeneity. Relevant clusters of genes that can discriminate between [PIP+] and [PIP-] cells were identified. Functional and regulatory network analyses based on a knowledge database revealed a master network of PIP co-modulated genes, including many interconnecting oncogenes and tumor suppressor genes, half of which were detected as differentially expressed through high-precision measurements. The network identified appears associated with an inhibition of proliferation coupled with an increase of apoptosis and an enhancement of cell adhesion in breast cancer cell lines, and contains many genes with a STAT5 regulatory motif in their promoters. CONCLUSIONS: Our global exploratory approach identified biological pathways modulated along with PIP expression, providing further support for its good prognostic value of disease-free survival in breast cancer. Moreover, our data pointed to the importance of a regulatory subnetwork associated with PIP expression in which STAT5 appears as a potential transcriptional regulator