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Threshold Analysis (threshold + analysis)
Selected AbstractsThreshold analysis of selected dose-response data for endocrine active chemicals,APMIS, Issue 3 2001Robert M. Blair Using a biologically relevant mathematical model, the Michaelis-Menten equation, we examined published data from endocrine active chemicals for evidence of no-threshold dose-response curves. Data were fit to a modified Michaelis-Menten equation which accounted for total background response. Subsequently, the data sets were analyzed using non-linear regression in order to estimate the four parameters of interest (non-hormone controlled background (Bnh), maximum response (Rmax), endogenous hormone level (D0), and the dose at which a half-maximal response was observed (ED50)) and to determine the fit to the fully modified Michaelis-Menten equation. Subsequently, response data were adjusted to account for Bnh and then normalized to Rmax, while dose data were adjusted to account for D0 and then normalized to the ED50. This data set was combined into a single, composite data set and fit to the fully modified Michaelis-Menten equation. We examined 31 data sets (24 endpoints) from studies on 9 different chemical/hormone treatments. Twenty-six of the data sets fit the modified Michaelis-Menten equation with high multiple correlation coefficients (r>0.90). The normalized data demonstrated a good fit to the modified Michaelis-Menten equation. These results indicate that a variety of biological responses fit the modified Michaelis-Menten equation, which does not have a threshold dose term. [source] Cost-effectiveness of HIV nonoccupational post-exposure prophylaxis in AustraliaHIV MEDICINE, Issue 4 2009D Guinot Objective The aim of the study was to determine the cost-effectiveness of HIV nonoccupational post-exposure prophylaxis (NPEP) in Australia. Methods A retrospective cost analysis of a population-based observational cohort of 1601 participants eligible for NPEP in Australia between 1998 and 2004 was carried out. We modelled NPEP treatment costs and combined them with effectiveness outcomes to calculate the cost per seroconversion avoided. We estimated the cost-utility of the programme, and sensitivity and threshold analysis was performed on key variables. Results The average NPEP cost per patient was A$1616, of which A$848 (52%) was for drugs, A$331 (21%) for consultations, A$225 (14%) for pathology and A$212 (13%) for other costs. The cost per seroconversion avoided in the cohort was A$1 647 476 in our base case analysis, and A$512 410 when transmission rates were set at their maximal values. The cost per quality-adjusted life-year (QALY) was between A$40 673 and A$176 772, depending on the risks of HIV transmission assumed. Conclusions In our base case, NPEP was not a cost-effective intervention compared with the widely accepted Australian threshold of A$50 000 per QALY. It was only cost-effective after receptive unprotected anal intercourse exposure to an HIV-positive source. Although NPEP was a relatively well-targeted intervention in Australia, its cost-effectiveness could be improved by further targeting high-risk exposures. [source] EVALUATION OF THE CHARACTER IMPACT ODORANTS IN SKIM MILK POWDER BY SENSORY STUDIES ON MODEL MIXTURESJOURNAL OF SENSORY STUDIES, Issue 1 2004Y. KARAGÜL-YÜCEER ABSTRACT The objective of this study was to verify key aroma-active compounds responsible for reconstituted fresh skim milk powder (SMP) aroma using threshold analysis, odor activity values, and model systems. Twelve odor-active compounds of SMP and one odor-active compound from fluid milk were selected based on flavor dilution factors from gas chromatography-olfactometry. Thresholds for the 13 odor-active compounds were identified using five-set ascending forced choice threshold analysis in odor-free water and fluid skim milk. Model systems were prepared using rehydrated milk retentate (RMR). The aroma of each model was evaluated by descriptive sensory analysis and by difference-from-control testing using a trained panel. The aroma of reconstituted fresh SMP and liquid skim milk were used as controls. Models containing a mixture of twelve of the thirteen chemicals had the most similar odor characteristics to rehydrated SMP aroma (9.0/10) indicating that these compounds constitute the character impact odorants of rehydrated fresh SMP. [source] Economic evaluation of BDP/formoterol fixed vs two single inhalers in asthma treatmentALLERGY, Issue 9 2010B. Brüggenjürgen To cite this article: Brüggenjürgen B, Ezzat N, Kardos P, Buhl R. Economic evaluation of BDP/formoterol fixed vs two single inhalers in asthma treatment. Allergy 2010; 65: 1108,1115. Abstract Background:, Asthma treatment costs are substantial, the largest proportion being incurred by medications. Combination therapy with inhaled corticosteroids (ICS) and long-acting beta2 -agonists (LABA) is recommended in patients not adequately controlled by ICS alone. Aim of this study was to compare costs and health outcomes of a fixed ICS,LABA combination of beclomethasone dipropionate (BDP) and formoterol fumarate (FF) vs the same drugs delivered via separate inhalers in Germany. Methods:, A cost-minimization analysis, a cost-effectiveness analysis, as well as a threshold analysis were undertaken. Efficacy results were obtained from a recent clinical trial. Cost inputs include medical costs, physician costs, and hospital admission costs. Medical costs, health outcomes, and treatment costs were also varied to assess their impact on results. Results:, Beclomethasone dipropionate/FF fixed combination was less costly compared to BDP + FF delivered as separate inhalers, costs totaling ,525 and ,637, respectively, over a 24-week treatment period. The incremental cost-effectiveness ratio was ,,9.77 per additional day free of asthma symptoms. Equal cost-effectiveness ratios would still be obtained at a price of the fixed combination increased by 3.4-fold. Conclusion:, A cost-minimization analysis as well as a cost-effectiveness analysis for Germany based on different product price calculations show that BDP/FF fixed combination is superior to BDP + FF delivered via separate inhalers. [source] Theory of laser cooling of semiconductor quantum wellsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2008G. Rupper Abstract We present a microscopic many-body theory of laser cooling of semiconductor quantum wells. The cooling mechanism is the upconversion of pump photons through absorption and subsequent luminescence by an electron,hole,exciton mixture maintained at steady state in the quantum well. Assuming this Coulomb plasma to be in quasi-thermal equilibrium, our theory calculates its absorption/luminescence spectra within a diagrammatic (real-time) Green's function approach at the self-consistent T-matrix level. These spectra are used in a cooling threshold analysis for GaAs quantum wells that also takes into account other losses into heat. We compare the present results with previous ones obtained for bulk GaAs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||