Practical and theoretical implications of target values in clinical chemistry: a QC approach

The automation of test validation procedures in a routine clinical laboratory by integrating artificial intelligence with the lab information system (LIS) is the focus of this study. Test validation consists of three layers: (1) acceptance of patient results based on technical criteria (technical validation), (2) acceptance of patient results based on internal quality control (QC) results (QC validation) and (3) medical validation of the patient protocol. The emphasis here is put on QC validation. General concepts regarding the setting of performance limits for internal QC results are briefly reviewed. As a practical example, we describe how the different layers of test validation were integrated with Molis, a LIS (Sysmex, Barchon, Belgium) used in a routine clinical biochemistry lab. PGP5 software (PGP, Brussels, Belgium) is used for technical validation and is installed on a Linx work-cell (Thermo Clinical Labsystems, Vantaa, Finland). The latter integrates four different Vitros instruments (OCD, Beerse, Belgium). QC validation and medical validation are performed with QC-Today (IL, Zaventem, Belgium) and VALAB (Erim, Toulouse, France), respectively. Both programs are bi-directionally coupled with the LIS. After 2 years of experience with this integrated system, it is clear that automation of validation rules and procedures has enhanced efficiency and overall quality of patient results.Presented at the Ninth Conference on Quality in the Spotlight, 18–19 March 2004, Antwerp, Belgium.     

Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce

The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primary–secondary amine and graphitized carbon black) and large-volume (20 μL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LC–MS–MS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GC–MS and LC–MS–MS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01 mg kg⁻¹ were achieved with both GC–MS (full-scan acquisition, 10 mg matrix equivalent injected) and LC–MS–MS (2 mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GC–MS (135 compounds) and LC–MS–MS (136 compounds) in over 100 different matrices, obtained over a period of 15 months, are also presented and discussed. At the 0.05 mg kg⁻¹ level acceptable recoveries were obtained for 93% (GC–MS) and 92% (LC–MS–MS) of pesticide–matrix combinations.     

Bias field reduction by localized Lloyd-Max quantization

Bias field reduction is a common problem in medical imaging. A bias field usually manifests itself as a smooth intensity variation across the image. The resulting image inhomogeneity is a severe problem for posterior image processing and analysis techniques such as registration or segmentation. In this article, we present a novel debiasing technique based on localized Lloyd-Max quantization (LMQ). The local bias is modeled as a multiplicative field and is assumed to be slowly varying. The method is based on the assumption that the global, undegraded histogram is characterized by a limited number of gray values. The goal is then to find the discrete intensity values such that spreading those values according to the local bias field reproduces the global histogram as good as possible. We show that our method is capable of efficiently reducing (even strong) bias fields in 3D volumes.     

Recent applications of liquid chromatography-mass spectrometry in forensic science

Recent years have seen the development of powerful technologies that have provided forensic scientists with new analytical capabilities, unimaginable only a few years ago. With liquid chromatography-mass spectrometry (LC-MS) in particular, there has been an explosion in the range of new products available for solving many analytical problems, especially for those applications in which non-volatile, labile and/or high molecular weight compounds are being analysed. The aim of this article is to present an overview of some of the most recent applications of LC-MS (/MS) to forensic analysis. To this end, our survey encompasses the period from 2002 to 2005 and focuses on trace analysis (including chemical warfare agents, explosives and dyes), the use of alternative specimens for monitoring drugs of abuse, systematic toxicological analysis and high-throughput analysis. It is not the intention to provide an exhaustive review of the literature but rather to provide the reader with a 'flavour' of the versatility and utility of the technique within the forensic sciences.