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A modified photometric method for the determination of phospholipase A activities which is based on a previously published reaction principle is described. The modified assay uses a lyophilized substrate emulsion rather than a freshly prepared phospholipid emulsion and a new chromogen (tribromohydroxybenzoic acid and 4-amino-antipyrine) with a high molar absorption coefficient (1,930 m2/mol at 546 nm, 2,900 m2/mol at 512 nm wavelength). The new test is more practicable with respect to pipetting volumes and incubation times. Preliminary results of a method evaluation indicate that the modified assay fulfills the usual criteria for clinical chemical enzyme measurements.

We report calculations of densities of states associated with specific local atomic configurations in substitutionally disordered transition-metal--noble-metal alloys, in particular Au-Pd alloys. These calculations are based on the fully relativistic version of the Korringa-Kohn-Rostoker coherent-potential approximation and on the recently developed corresponding embedded-cluster method, and allow a direct evaluation of short-range-order effects in substitutionally disordered materials. A discussion of our results and a comparison with results obtained for transition-metal alloys such as Pd-Ag is given.

Reference samples consisting of spray-dried milk artificially contaminated with Salmonella typhimurium II 505 contained in a gelatin capsule have been developed to evaluate the standard method for the detection of Salmonellae in foods and feeding stuffs. The present study was carried out to evaluate these reference samples. Salmonella isolations from reference samples in the absence of food were satisfactory in 4 out of 6 laboratories when Muller-Kauffmann tetrathionate broth prepared according to ISO-6579 (TBB-ISO) was used and in all laboratories when the secondary enrichment medium was the magnesium chloride-malachite green broth of Rappaport-Vassiliadis (RV). The proportion of Salmonella isolations from reference samples decreased from 80% to 47% with TBB-ISO and from 95% to 63% with RV in the presence of food. Most negative results were obtained with foods such as minced pork and minced beef, which had high aerobic and Enterobacteriaceae plate counts. It is concluded that the reference samples can be used to test the performance of media and the reproducibility of methods when it is used without the addition of food. The results obtained for Salmonella isolations in the presence of food questioned the role of numbers and types of competitive micro-organisms. In particular these latter results indicated that more research is needed to gain a better understanding of the Salmonella isolation procedure.

A new deconvolution algorithm (DCON) suitable for pharmacokinetic applications is presented. It requires that both the impulse and input responses, typically systemic drug levels, be well described by polyexponential equations. DCON has a wider range of applications than an earlier method (DECONV) from which it is derived. A FORTRAN program is provided, making implementation of the technique a simple matter. DCON is demonstrated to evaluate the “GI bioavailability,” defined as the rate and the extent of gastrointestinal drug release, of various ibuprofen dosage forms. The GI drug release kinetics exemplifies a pharmacokinetic system which cannot be evaluated using the previous deconvolution algorithm (DECONV) because of an initial zero drug level response. This limitation is not found in DCON. It is also demonstrated how the mean in vivo dissolution time MDT can be evaluated by deconvolution.

Achieving precision and accuracy in routine clinical analyses is a complex task, requiring the identification, estimation, and elimination of sources of analytical error. This review first considers concepts of precision and accuracy, including discussions of the meaning of measurement process, analytical method, state of statistical control, precision, imprecision, accuracy, inaccuracy, systematic error, overall or total error, true value, traceability, and compatability. These concepts provide the basis upon which the performance of analytical methods can be evaluated. The second part of the review considers how precision and accuracy are assessed by the use of method evaluation experiments. The approach emphasizes the development of an evaluation protocol based on the analytical characteristics which represent the performance of the method. This includes discussions of the familiarization period; testing analytic range and linearity; testing precision by a replication experiment; testing accuracy by recovery, interference, and comparison of methods experiments; the selection of a comparative analytical method; the statistical analysis of method comparison data, including the interpretation of that data; the collaborative testing.

INTRODUCTION The quality of neonatal care is mainly determined by long-term neurodevelopmental outcome. The neurodevelopment of preterm infants is related to postnatal head growth and depends on medical interventions such as nutritional support. Head circumference (HC) is currently used as a two-dimensional measure of head growth. Since head deformities are frequently found in preterm infants, HC may not always adequately reflect head growth. Laser aided head shape digitizers offer semiautomatic acquisition of HC and cranial volume (CrV) and could thus be useful in describing head size more precisely. AIMS 1) To evaluate reproducibility of a 3D digital capture system in newborns. 2) To compare manual and digital HC measurements in a neonatal cohort. 3) To determine correlation of HC and CrV and predictive value of HC. METHODS Within a twelve-month period data of head scans with a laser shape digitizer were analysed. Repeated measures were used for method evaluation. Manually and digitally acquired HC was compared. Regression analysis of HC and CrV was performed. RESULTS Interobserver reliability was excellent for HC (bias-0.005%, 95% Limits of Agreement (LoA) -0.39-0.39%) and CrV (bias1.5%, 95%LoA-0.8-3.6%). Method comparison data was acquired from 282 infants. It revealed interchangeability of the methods (bias-0.45%; 95%LoA-4.55-3.65%) and no significant systematic or proportional differences. HC and CrV correlated (r(2) = 0.859, p

BACKGROUND:In order to improve the health and survival of mothers/newborns, the quality and attendance rates of postpartum care (PPC) must be increased, particularly in low-resource settings.OBJECT ...

Brain imaging genetics is an emergent research field where the association between genetic variations such as single nucleotide polymorphisms (SNPs) and neuroimaging quantitative traits (QTs) is evaluated. Sparse canonical correlation analysis (SCCA) is a bi-multivariate analysis method that has the potential to reveal complex multi-SNP-multi-QT associations. We present initial efforts on evaluating a few SCCA methods for brain imaging genetics. This includes a data synthesis method to create realistic imaging genetics data with known SNP-QT associations, application of three SCCA algorithms to the synthetic data, and comparative study of their performances. Our empirical results suggest, approximating covariance structure using an identity or diagonal matrix, an approach used in these SCCA algorithms, could limit the SCCA capability in identifying the underlying imaging genetics associations. An interesting future direction is to develop enhanced SCCA methods that effectively take into account the covariance structures in the imaging genetics data.

From the moment theory of light beam propagation and reflection Fresnel formulae at a planar interface between two dielectric media, we find simple approximate analytical expressions for the angular and lateral shifts for partial and total reflection of ligh beams of finite transversal extent and arbitrary spatial form. A new lateral shift for partial reflection for asymmetric incident beams is found.

Judging the medical acceptability and comparing the medical utility of laboratory methods requires standards for reproducibility with regard to medical performance. A completely general and flexible performance standard for reproducibility consists of the reproducibility criterion, the allowable error, and the concentration value. Neither precision, accuracy, nor total error correctly addresses this standard. The medical utility frequency of a method does do so, however, its use making method evaluation and comparison simple, completely flexible, and exact.

Because inadequate clinical testing may expose the public to unwarranted toxic effects a review of current clinical testing methodology is made and recommendatiosn for improvements are given. Areas covered include evaluation of data analysis procedures evaluation of the role of research design and some specific problems in contraceptive method evaluation. Recommendations call for greater standardization and for the development of new methodology in clinical testing data analysis and research design. Immediate steps to achieve this end include technical assistance from supporting agencies inclusion of clinical research methodology in training programs discussion of methodology in scientific forums advice from Journal editors and reviewers on methodology. At the international level those responsible for programs at universities and other institutions should ensure adequate technical assistance in methodology when encouraging clinical studies.

The last edition of Tietz's Fundamentals of Clinical Chemistry appeared more than ten years ago and survives as a dated but valuable reference. The successor to Fundamentals, Textbook of Clinical Chemistry , follows an outline similar to the original text but adds many new subjects and updates older topics. This has resulted in a text that is 50% larger than its predecessor. Much of the newer material centers on interpretation and understanding of data and its limitations. For example, more than 200 pages (compared with 50 pages) are dedicated to an introductory section entitled "Acquisition, Management, and Application of Laboratory Data," covering the use of reference ranges, statistics, quality assurance, method evaluation, and computers. The remaining introductory chapters discuss general procedures, instrumentation, and automation. Unfortunately, the chapter that discusses current automated instrumentation already has been outdated by equipment evolution and could have been incorporated into the chapter about general instrumentation principles.