PubMed · 9634982
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P L Emond, C J Corbett. 1998. A new method for measuring human basic tear fluid osmolality.. https://doi.org/10.1007/978-1-4615-5359-5_124
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Ex vivo production of hematopoietic progenitor cells has potential applications for cell therapy to alleviate cytopenias associated with chemotherapy and for gene therapy. In both therapies, progenitor and stem cells are considered crucial factors for therapeutic success. Assays for progenitor cells, however, take 2 weeks to complete, which is similar to the length of a typical culture. Therefore, a real-time estimation of the percentage or number of progenitor cells, based on rapid measurements, would be useful for optimization of feeding and harvest decisions. In this study, metabolic activity assays and flow cytometric analysis were used to estimate the content of progenitor cells. The measured metabolic activities are a collective contribution from all types of cells. Cells in granulomonocytic cultures have been lumped into six cell types and metabolic rates have been modeled as a linear function of cell composition and growth rate and as a nonlinear function of cell density. Data from 24 experiments were utilized to determine the model parameters in a calibration step. These data include flow cytometric analysis of more mature hematopoietic cells, progenitor cell colony assays, total cell content, and metabolite concentrations, and cover a wide range of cell composition, cell density, and growth rate. After calibration, the model is able to deliver good predictions of progenitor cell content for cultures with higher percentages of progenitor cells, as well as the peak progenitor cell content, based only on parameters that can be rapidly measured. With the aid of those predictions a harvest strategy was developed that will allow optimizing the harvest time based on the culture kinetics of each patient or donor inoculum, rather than using retrospective analysis to determine a uniform harvest time.
The problem of assessing the validity and value of prognostic survival models presented in the literature for a particular population for which some data has been collected is discussed. Methods are sketched to perform validation through 'calibration', that is by embedding the literature model in a larger calibration model. This general approach is exemplified for x-year survival probabilities, Cox regression and general non-proportional hazards models. Some comments are made on basic structural changes to the model, described as 'revision'. Finally, general methods are discussed to combine models from different sources. The methods are illustrated with a model for non-Hodgkin's lymphoma validated on a Dutch data set.
Qualitative variables are commonly measured by means of different types of rating scales that produce ordered categorical data. The number of response categories in a scale can be chosen arbitrarily according to different operational definitions of the attribute to be measured. In the present paper classical measures based on the difference between the probabilities of concordant and discordant pairs of classifications were compared with a novel approach for assessment of order consistency between rating scales. In the new approach, illustrated by an assessment of pain, the concordant and discordant pairs are related to the pattern of total order consistency, irrespective of the scaling and the categorical distributions. The level of order consistency between a visual analogue scale (VAS) and a discrete scale for the same variable was evaluated. The non-linear properties of VAS assessments were demonstrated. The inter-scale consistency between the discrete scale and different approaches to grouping VAS responses into discrete scales showed that equidistant rescaling of VAS assessments resulted in an inter-scale bias.